Mask blanks for pattern evaluation

Abstract

To simply perform drawing evaluation.SOLUTION: A mask blank for drawing evaluation 10 evaluates drawing performance for a reflection type mask blank used in EUV lithography, and has a substrate 11, a pseudo reflection layer 12 laminated on the substrate, and a hard mask layer 16 laminated on the pseudo reflection layer 12. The pseudo reflection layer is a single layer film which is made of a material equivalent to a multilayer reflection film for EUV, and the hard mask layer is a layer equivalent to a layer being a mask to an absorber layer for EUV.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mask blank for pattern evaluation, and in particular to a technique suitable for use in EUV lithography. [Background technology]

[0002] In recent years, in the manufacture of semiconductors, along with the miniaturization of devices, EUV lithography, an exposure technology using extreme ultraviolet (EUV: Extreme Ultra Violet) light, is seen as promising. Note that here, EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically light with a wavelength of about 0.2 to 100 nm.

[0003] A reflective mask used in EUV lithography has a multilayer reflective film formed on a substrate that reflects exposure light, and an absorber film that absorbs the exposure light formed in a pattern on the multilayer reflective film. Light incident on a reflective mask mounted on an exposure machine (a writing machine or a pattern transfer device) is absorbed in areas with the absorber film, and in areas without the absorber film, the light image reflected by the multilayer reflective film is transferred onto a semiconductor substrate through a reflection optical system.

[0004] As a multilayer reflective film, for example, one that reflects 13-14 nm EUV light and is made by alternately stacking Mo and Si layers of several nm in thickness for about 40 to 60 periods is known. In order to increase the reflectance, it is desirable to use a Mo film with a large refractive index as the top layer, but Mo is easily oxidized when exposed to air, resulting in a decrease in reflectance. Therefore, for example, a Si film is provided as the top layer as a protective film to prevent oxidation.

[0005] In addition, a reflective mask is known in which a buffer layer made of ruthenium (Ru) is formed between a multilayer reflective film in which Mo films and Si films are alternately stacked, and an absorber pattern in order to prevent etching damage to the multilayer reflective film during formation of the absorber pattern.

[0006] Unlike actual EUV lithography, the mask blanks used in EUV lithography are also used to maintain the drawing characteristics of the drawing machine, that is, the performance of the drawing machine in pattern formation.

[0007] In other words, mask blanks used in EUV lithography need to be verified for their adhesion to the resist during pattern formation, and for EB (electron beam) exposure, their behavior with respect to the electron beam. In particular, verification of the lithography machine characteristics that form masks from mask blanks needs to be performed after maintenance of the lithography machine or after the completion of a certain number of EUV lithography processes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2013-532381 Summary of the Invention [Problem to be solved by the invention]

[0009] However, as described above, the mask blanks used in EUV lithography have a multilayer reflective film, which is a laminate of an extremely large number of Mo films and Si films alternately stacked, and therefore the manufacturing process is complicated and the manufacturing cost is very high. Moreover, in forming such a large number of layers, it is necessary to maintain a state in which the uniformity of the film thickness and the uniformity of the film properties are guaranteed over the entire surface during each stacking of the multiple layers, so that the manufacturing is time-consuming and the cost increases when using it to verify the characteristics of a lithography machine other than the actual EUV lithography, so there was a demand for an alternative method. In other words, there was a demand to use mask blanks for verifying the characteristics of a lithography machine, i.e., mask blanks for lithography evaluation, rather than mask blanks used in actual EUV lithography.

[0010] The present invention has been made in consideration of the above circumstances, and aims to achieve the following objects. 1. To provide a mask blank for patterning evaluation that enables evaluation of patterning machine characteristics. 2. To make it possible to provide mask blanks for patterning evaluation with a simple structure, with ease of manufacture, and at low cost. 3. Be sure to evaluate the drawing characteristics. [Means for solving the problem]

[0011] The mask blank for patterning evaluation of the present invention is A mask blank for lithography evaluation to evaluate EB lithography performance for a reflective mask blank used in EUV lithography, A substrate; a false reflective layer laminated to the substrate; a hard mask layer laminated to the false reflective layer; having The false reflective layer is a single layer film made of a material equivalent to a multilayer reflective film for EUV, The hard mask layer is a layer equivalent to a layer that serves as a mask for an absorber layer against EUV, The thickness of the false reflective layer is 10 nm to 100 nm; The hard mask layer and the false reflective layer are The hard mask layer is used as a mask to pattern the false reflective layer, and the pattern dimension can be evaluated. Film Thickness In comparison It is set, This has solved the above problem. Books The mask blank for pattern evaluation of the invention is A resist layer is laminated on the hard mask layer. It is possible. The mask blank for patterning evaluation of the present invention is The false reflective layer contains molybdenum and silicon, and the concentration of impurities other than oxygen and carbon is 20 ppm or less; It is possible. The mask blank for patterning evaluation of the present invention is The hard mask layer contains chromium and has a thickness of 1 nm to 20 nm. It is possible. The mask blank for patterning evaluation of the present invention is an absorber layer laminated to the false reflective layer; The hard mask layer is laminated to the absorber layer. It is possible. The mask blank for patterning evaluation of the present invention is a protective layer laminated to the false reflective layer; The absorbent layer is laminated on the protective layer. It is possible. The mask blank for patterning evaluation of the present invention is A buffer layer is laminated on the protective layer, The absorber layer is laminated on the buffer layer. It is possible. The mask blank for patterning evaluation of the present invention is The substrate is a quartz substrate, or the substrate is a zero expansion substrate; It is possible. The drawing evaluation method of the present invention includes: Using any one of the above described mask blanks for pattern evaluation, forming a resist pattern by performing writing and development using an electron beam writing device, or by etching the hard mask layer to form a pattern, and then removing the resist layer, measuring the pattern dimensions using a CD-SEM to evaluate the writing characteristics; It is possible.

[0012] The mask blank for patterning evaluation of the present invention is A mask blank for lithography evaluation to evaluate EB lithography performance for a reflective mask blank used in EUV lithography, A substrate; a false reflective layer laminated to the substrate; a hard mask layer laminated to the false reflective layer; having The false reflective layer is a single layer film made of a material equivalent to a multilayer reflective film for EUV, The hard mask layer is the same layer that serves as a mask for the absorber layer against EUV. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, as a drawing characteristic, it is possible to evaluate the adhesion between the resist layer and hard mask layer formed when forming a pattern from a mask blank as a mask. In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, the manufacturing process is simplified and the mask blanks can be easily manufactured, the manufacturing time and manufacturing cost are reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0013] The mask blank for patterning evaluation of the present invention is A resist layer is laminated onto the hard mask layer. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, as a drawing characteristic, it is possible to evaluate the adhesion between the resist layer and hard mask layer formed when forming a pattern from a mask blank as a mask. In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, since the mask blank for pattern evaluation has a single-layered false reflective layer instead of a multilayer reflective film, it is not necessary to form a multilayer reflective film, which is difficult to form when the defect specifications are satisfied. Therefore, the mask blank for pattern evaluation of the present invention can be easily manufactured by simplifying the manufacturing process compared to the reflective mask blank used in EUV lithography, and the manufacturing time and manufacturing cost can be reduced, and pattern characteristics can be easily evaluated.

[0014] The mask blank for patterning evaluation of the present invention is The false reflective layer contains molybdenum and silicon. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which have a complex structure and require extremely strict manufacturing conditions. Specifically, as drawing characteristics, when forming a pattern from a mask blank as a mask, a false reflective layer with the same composition as the multilayer reflective film that affects the absorber layer, etc. is formed, and the adhesion of each layer laminated on the multilayer reflective film can be evaluated. In addition, as the drawing characteristics of each layer stacked on the multilayer reflective film, it is possible to evaluate whether the spread and amount of backscattered electrons from each layer against the incident electron beam when EB exposure is performed are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, since the mask blank for pattern evaluation has a single false reflective layer having the same composition as the multilayer reflective film, it is not necessary to form a multilayer reflective film, which is difficult to form, when the defect specification is satisfied. Therefore, the mask blank for pattern evaluation of the present invention can be easily manufactured by simplifying the manufacturing process compared to the reflective mask blank used in EUV lithography, and the manufacturing time and manufacturing cost can be reduced, and the patterning characteristics can be easily evaluated.

[0015] The mask blank for patterning evaluation of the present invention is The hard mask layer contains chromium. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, when forming a pattern from a mask blank as a mask, it is possible to evaluate the adhesion and etching characteristics as pattern formation characteristics of the hard mask layer formed as the drawing characteristics. In addition, it is possible to evaluate whether the etching characteristics of the hard mask layer when patterning each layer stacked on the multilayer reflective film, and the spread and amount of backscattered electrons from each layer against the incident electron beam when EB exposure is performed as drawing characteristics, are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, the mask blank for drawing evaluation has a single-layer pseudo-reflective layer instead of a multilayer reflective film, and the hard mask layer for pattern formation of other layers can have properties equivalent to those of the reflective mask blanks used in EUV lithography. Furthermore, since the mask blank for pattern evaluation has a single-layered false reflective layer instead of a multilayer reflective film, it is not necessary to form a multilayer reflective film, which is difficult to form when the defect specifications are satisfied. Therefore, the mask blank for pattern evaluation of the present invention can be easily manufactured by simplifying the manufacturing process compared to the reflective mask blank used in EUV lithography, and the manufacturing time and manufacturing cost can be reduced, and pattern characteristics can be easily evaluated.

[0016] The mask blank for patterning evaluation of the present invention is an absorber layer laminated to the false reflective layer; The hard mask layer is deposited on the absorber layer. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which have a complex structure and require extremely strict manufacturing conditions. Specifically, when forming a pattern from a mask blank as a mask, it is possible to evaluate the characteristics in pattern formation in the absorber layer, which is the most important as a mask, as the drawing characteristics. In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, the manufacturing process is simplified and the mask blanks can be easily manufactured, the manufacturing time and manufacturing cost are reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0017] The mask blank for patterning evaluation of the present invention is a protective layer laminated to the false reflective layer; The absorbent layer is laminated to the protective layer. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which have a complex structure and require extremely strict manufacturing conditions. Specifically, when forming a pattern from a mask blank as a mask, it is possible to evaluate the characteristics in pattern formation in the protective layer, which is an important element of a mask, as the drawing characteristics. In addition, in terms of drawing characteristics, it is possible to evaluate whether the behavior of the incident electron beam when performing EB exposure, i.e., the spread and amount of backscattered electrons, is equivalent to that of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, the manufacturing process is simplified and the mask blanks can be easily manufactured, the manufacturing time and manufacturing cost are reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0018] The mask blank for patterning evaluation of the present invention is A buffer layer is laminated on the protective layer, The absorber layer is laminated to the buffer layer. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, when forming a pattern from a mask blank as a mask, it is possible to evaluate the characteristics in pattern formation in the buffer layer, which is important as a mask, as drawing characteristics. In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, the manufacturing process is simplified and the mask blanks can be easily manufactured, the manufacturing time and manufacturing cost are reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0019] The mask blank for patterning evaluation of the present invention is The substrate is a quartz substrate. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision using inexpensive quartz substrates, without using reflective mask blanks using zero expansion substrates used in EUV lithography, which requires extremely strict conditions. Specifically, when forming a pattern from a mask blank as a mask, the drawing characteristics can be evaluated using a quartz substrate, which has a wealth of processing methods as a mask substrate and is often used for mask blanks that are compatible with light of different wavelengths. In addition, as a drawing characteristic, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed on a quartz substrate when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, compared with the reflective mask blanks used in EUV lithography, the manufacturing process is simplified and the mask blanks can be easily manufactured without using a zero expansion substrate, which is difficult to process and requires a large number of manufacturing steps, and the manufacturing time and manufacturing costs can be reduced, making it easy to evaluate the patterning characteristics.

[0020] The mask blank for patterning evaluation of the present invention is The substrate is a zero expansion substrate. This makes it possible to evaluate the drawing performance of reflective mask blanks used in EUV lithography with the same accuracy and precision, without using reflective mask blanks used in EUV lithography, which have a complex structure and require extremely strict manufacturing conditions.Specifically, by using a zero-expansion substrate with the same thermal properties as the reflective mask blanks used in EUV lithography, the characteristics in pattern formation in each layer of the mask can be evaluated when forming a pattern from the mask blank as a mask as the drawing characteristics. In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography. Furthermore, in the mask blanks for patterning evaluation, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks for patterning evaluation of the present invention, the manufacturing process is simplified and the mask blanks can be easily manufactured, the manufacturing time and manufacturing cost are reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0021] The drawing evaluation method of the present invention includes: Using any one of the above described mask blanks for pattern evaluation, A resist pattern is formed by drawing and developing with an electron beam drawing device (EB drawing machine), or the hard mask layer is etched to form a pattern, and after removing the resist layer, the pattern dimensions are measured with a CD-SEM (Critical Dimension-Scanning Electron Microscope) to evaluate the drawing characteristics. As a result, it is not necessary to form a multilayer reflective film, which is difficult to form when the defect specifications are met, and the manufacturing process can be simplified and the mask blanks can be manufactured more easily than the reflective mask blanks used in EUV lithography.The mask blanks for patterning evaluation can be used to easily evaluate patterning characteristics, with reduced manufacturing time and costs. Effect of the Invention

[0022] According to the present invention, it is possible to provide a mask blank for patterning evaluation which can be easily manufactured by simplifying the manufacturing process, reducing the manufacturing time and manufacturing costs, and enabling easy evaluation of patterning characteristics, as compared to the reflective mask blanks used in EUV lithography. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view showing a first embodiment of a mask blank for patterning evaluation according to the present invention. [Diagram 2] 1A to 1C are cross-sectional views showing a patterning evaluation step using a first embodiment of a mask blank for patterning evaluation according to the present invention. [Diagram 3] FIG. 2 is a cross-sectional view showing a second embodiment of a mask blank for patterning evaluation according to the present invention. [Figure 4] 5A to 5C are cross-sectional views showing a patterning evaluation step using a second embodiment of a mask blank for patterning evaluation according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, a first embodiment of a mask blank for patterning evaluation according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a mask blank for drawing evaluation in this embodiment, and in the figure, reference numeral 10 denotes the mask blank for drawing evaluation.

[0025] The mask blank 10 for writing evaluation according to this embodiment is a pseudo mask blank for evaluating writing performance. That is, the writing performance is evaluated when performing patterning in the mask blank, that is, a writing process performed when manufacturing a mask from the mask blank.

[0026] In particular, the drawing evaluation mask blank 10 according to this embodiment is used for evaluation in lithography using extreme ultraviolet light (EUV) having a wavelength of about 0.2 to 100 nm, preferably about 13.5 nm, as exposure light.

[0027] The mask blanks 10 for patterning evaluation according to this embodiment are used for EUV reflective mask blanks. That is, the mask blanks 10 for patterning evaluation according to this embodiment are not actually used as a mask, and do not need to have a reflectivity to the above-mentioned exposure light.

[0028] As shown in FIG. 1, the mask blank 10 for drawing evaluation in this embodiment has a substrate 11, a false reflective layer 12 formed on the substrate 11, a protective layer 13 formed on the false reflective layer 12, a buffer layer 14 formed on the protective layer 13, an absorber layer 15 formed on the buffer layer 14, a hard mask layer 16 formed on the absorber layer 15, and a resist layer 17 formed on the hard mask layer 16.

[0029] The substrate 11 is a quartz substrate (glass substrate). The glass substrate is made of a material having excellent resistance to EUV irradiation, such as a quartz glass substrate. The size of the substrate 11 is not particularly limited, and is appropriately selected according to the substrate to be exposed using the lithography (semiconductor substrate, substrate for FPD such as LCD (liquid crystal display), plasma display, organic EL (electroluminescence) display, etc.).

[0030] In this embodiment, a rectangular substrate with sides of about 100 mm to 2000 mm or more and a thickness of about 1 mm can be used as the substrate 11. The substrate 11 can have a surface condition equivalent to that of an EUV mask blank, for example, a smooth surface of 0.15 nm rms or less, preferably 0.1 nm rms or less, and a flatness of 100 nm or less, preferably 70 nm or less.

[0031] In the mask blank 10 for patterning evaluation according to this embodiment, when quartz glass is used as the substrate 11, it can have the same characteristics as a mask blank used with exposure light having a longer wavelength. This allows the substrate procurement cost and the work procedures such as surface treatment in the pre-processing of the substrate to be the same as in the past, and makes it easier to handle the substrate.

[0032] Since the substrate 11 according to this embodiment is applicable to the evaluation of reflective mask blanks, transparency is not important. The substrate 11 according to this embodiment may be zero-expansion glass (zero-expansion substrate) like the reflective mask blanks using EUV. Here, the zero expansion glass is selected from those that are not significantly affected by thermal expansion during lithography even when the temperature rises due to EUV irradiation.

[0033] Specifically, the substrate 11 has a low thermal expansion coefficient (0±1.0×10 -7 / °C, more preferably 0±0.3×10 -7 / °C, and more preferably 0±0.2×10 -7 / °C, and more preferably 0±0.1×10 -7 / °C, and 0±0.05×10 is particularly preferable. -7 / ° C. In addition, it is preferable that the surface has excellent smoothness, flatness, and resistance to a cleaning solution used for cleaning a mask blank or an EUV mask after forming a mask pattern.

[0034] Specifically, the substrate 11 may be made of glass having a low thermal expansion coefficient, such as SiO2-TiO2 glass, but is not limited thereto. Substrates may also be made of crystallized glass in which β-quartz solid solution is precipitated, quartz glass, silicon, metal, etc. A film such as a stress compensation film may also be formed on the substrate. An example of a metal substrate is an Invar alloy (Fe-Ni alloy).

[0035] The substrate 11 is preferably a substrate having high smoothness and flatness. In particular, it is preferable that the substrate has a smooth surface of 0.2 nmRms or less (smoothness in a 10 μm square area) and a flatness of 100 nm or less (flatness in a 142 mm square area). In addition, the substrate 11 is preferably one having high rigidity to prevent deformation due to film stress of the film formed thereon. In particular, it is preferable that the substrate has a high Young's modulus of 65 GPa or more.

[0036] The unit of smoothness, Rms, is the root-mean-square roughness, which can be measured with an atomic force microscope. Flatness is a value that indicates the surface warpage (amount of deformation) indicated by TIR (Total Indicated Reading), and is the absolute value of the difference in height between the highest point on the substrate surface above the focal plane, which is determined by the least squares method with the substrate surface as the reference plane, and the lowest point on the substrate surface below the focal plane.

[0037] The false reflective layer 12 is a single layer film containing the same elements as the multilayer reflective film of the EUV mask blanks as the patterning evaluation mask blanks 10. The multilayer reflective film of the EUV mask blanks is a kind of Bragg reflection mirror for EUV light.

[0038] That is, the pseudo-reflective layer 12 can be a single layer film made of the same combination of elements as the multilayer reflective film, such as Mo / Si, Ru / Si, Mo / Be, Rh / Si, Pt / Si, Mo compound / Si compound, Si / Mo / Ru, Si / Mo / Ru / Mo, Si / Ru / Mo / Ru, etc. The pseudo-reflective layer 12 can be a single layer film containing molybdenum and silicon. This is because by using a film containing the same elements as the multilayer reflective film, the amount and range of backscattering of the electron beam during EB exposure in the drawing performance evaluation becomes equivalent to that of the multilayer reflective film, thereby satisfying the condition of minimizing the modification of the proximity effect correction.

[0039] Here, the pseudo-reflective layer 12 is preferably a single-layer film containing the same elements as the multi-layer reflective film, so for example, in the case of Mo / Si, it is preferable that it does not contain impurities other than molybdenum and silicon. Specifically, it is preferable that the concentration of impurities other than molybdenum and silicon is 20 ppm or less (other than oxygen and carbon).

[0040] The thickness of the false reflective layer 12 can be 10 nm to 100 nm, more preferably 25 nm to 40 nm. This is because the hard mask layer 16 itself has a low evaluation accuracy of the pattern dimension by CD-SEM due to the thin thickness of the hard mask layer 16, and the pattern dimension may be evaluated by etching the false reflective layer 12 with the patterned hard mask layer 16, so the condition of keeping the thickness ratio defined by the etching selectivity between the hard mask layer 16 and the false reflective layer 12 constant is satisfied. Therefore, if the thickness is smaller than the above range, it is not preferable because there is a problem that the evaluation accuracy decreases, and if the thickness is larger than the above range, it is not preferable because there is a problem that the hard mask layer 16 disappears before the end point and the pattern shape deteriorates.

[0041] The single layer false reflective layer 12 can be formed on the substrate 11 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0042] The single layer of the false reflective layer 12 may have a gradient in composition in the thickness direction. For example, the gradient may be such that the Si concentration increases toward the top surface of the false reflective layer 12, that is, toward the direction farthest from the substrate 11. In this case, as described later, the protective layer 13 and the buffer layer 14 may not be provided.

[0043] In the reflective mask blank, a protective film can be provided on the multilayer reflective film in order to prevent the surface of the multilayer reflective film and its vicinity from natural oxidation during storage or oxidation during cleaning.

[0044] The protective layer 13 in the mask blank 10 for patterning evaluation according to this embodiment is equivalent to a protective film in a reflective mask blank. The protective layer 13 may be made of, for example, ruthenium (Ru) or a ruthenium compound containing ruthenium (Ru) and at least one selected from molybdenum (Mo), niobium (Nb), zirconium (Zr), yttrium (Y), boron (B), titanium (Ti), and lanthanum (La), or may be Si, Ru, Rh, C, SiC, a mixture of these elements, or these elements to which nitrogen or boron has been added.

[0045] When Ru is used as the protective layer 13, it can also function as a buffer film, which will be described later, so it is possible to omit providing the buffer layer 14. In this case, the Ru film can be about 2 nm to 3 nm, or about 2.5 nm. When Si is used as the protective layer 13, the uppermost surface of the false reflective layer 12 can function as the protective layer 13 by forming the uppermost surface of the false reflective layer 12 from Si. In this case, it is also possible to omit the Si protective layer 13. In order for the Si film on the uppermost surface of the false reflective layer 12 to also function as a protective film, it is preferable that the film thickness of the Si film is 5 to 15 nm, which is thicker than 4.5 nm.

[0046] Alternatively, after a Si film is formed as the protective layer 13, a Ru film serving as both the protective layer 13 and the buffer layer 14 may be formed on the Si film. The films such as the protective layer 13 and the buffer layer 14 do not necessarily have to be one layer, but may be two or more layers. Furthermore, the films such as the protective layer 13 and the buffer layer 14 may have a concentration gradient in the film thickness direction. Furthermore, the films such as the protective layer 13 and the buffer layer 14 may contain impurities other than those mentioned above.

[0047] When the protective film is provided on a multilayer reflective film, the maximum reflectance of the protective film surface to EUV light must satisfy the following range. That is, the maximum reflectance of the protective film surface to EUV light is preferably 60% or more, and more preferably 65% ​​or more. Therefore, it is preferable that the protective layer 13 also satisfies this condition.

[0048] The buffer layer 14 in the mask blank 10 for patterning evaluation according to this embodiment is equivalent to a buffer film in a reflective mask blank. The buffer layer 14 has etching characteristics different from those of the absorber layer 15. The buffer layer 14 is equivalent to a buffer film in a reflective mask blank. The buffer film is capable of preventing damage to the multilayer reflective film caused by etching during pattern formation and pattern correction of the absorber film.

[0049] The buffer layer 14 can be a chromium-based film containing chromium (Cr) that has different etching characteristics from the absorber film. The chromium-based buffer film has high smoothness, and the absorber film formed thereon also has a high smoothness on its surface, thereby reducing pattern blur.

[0050] The material of the buffer film is selected to be less susceptible to the etching process of the absorbing film, that is, to have an etching rate slower than that of the absorbing film and to be less susceptible to damage by this etching process. The buffer layer 14 can be formed on the protective layer 13 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0051] Examples of materials for the buffer film include Cr, Al, Ru, Ta, and their nitrides, as well as SiO2, Si3N4, Al2O3, and mixtures thereof. Among these, Ru, CrN, and SiO2 are preferred, CrN and Ru are more preferred, and Ru is particularly preferred because it functions as both a protective film and a buffer film. The thickness of the buffer film is preferably 1 to 60 nm, particularly preferably 1 to 10 nm, and further preferably 1 to 5 nm.

[0052] The absorber layer 15 in the mask blank 10 for drawing evaluation according to this embodiment is equivalent to an absorber film in a reflective mask blank. The absorber layer 15 has a function of absorbing exposure light, such as EUV light, and can be preferably made of tantalum (Ta) alone or a material containing Ta as a main component. A material containing Ta as a main component is usually a Ta alloy. The crystal state of such an absorber film is preferably an amorphous or microcrystalline structure in terms of smoothness and flatness. Examples of materials containing Ta as a main component include materials containing Ta and B, materials containing Ta and N, materials containing Ta and B and further containing at least one of O and N, materials containing Ta and Si, materials containing Ta, Si and N, materials containing Ta and Ge, materials containing Ta, Ge and N, etc.

[0053] By adding B, Si, Ge, etc. to Ta, an amorphous material can be easily obtained and the smoothness can be improved. Also, by adding N or O to Ta, the resistance to oxidation is improved, which has the effect of improving stability over time. Particularly preferred materials among these include, for example, materials containing Ta and B (composition ratio Ta / B is in the range of 8.5 / 1.5 to 7.5 / 2.5) and materials containing Ta, B and N (N is 5 to 30 at %, and B is 10 to 30 at % when the remaining components are taken as 100). With these materials, a microcrystalline or amorphous structure can be easily obtained, and good smoothness and flatness can be obtained.

[0054] Such an absorber film containing Ta as a single component or Ta as a main component is preferably formed by a sputtering method such as magnetron sputtering. For example, in the case of a TaBN film, a target containing tantalum and boron is used, and the film can be formed by a sputtering method using argon gas with added nitrogen. When formed by a sputtering method, the internal stress can be controlled by changing the power input to the sputtering target or the input gas pressure. In addition, since it can be formed at a low temperature of about room temperature, the influence of heat on the multilayer reflective film, etc. can be reduced.

[0055] Examples of materials for the absorber layer 15 include materials such as WN, TiN, and Ti, other than materials containing Ta as a main component. The absorbent layer 15 may have a laminated structure of multiple layers. The absorber layer 15 may have a thickness that can sufficiently absorb the exposure light, for example, EUV light, and can be about 30 to 100 nm.

[0056] The characteristic that is particularly required for the absorber film in the reflective mask blank is that the optical contrast of the EUV reflected light is sufficiently high in relation to the multilayer reflective film (or in relation to the protective film if a protective film is formed on the multilayer reflective film). To achieve the above characteristic, it is preferable to make the reflectance of EUV light on the absorber film surface extremely low. However, it is required to make the thickness of the absorber film thin.

[0057] For this reason, it is not realistic to sufficiently increase the optical contrast of the reflected EUV light only by reducing the reflectance of the EUV light on the absorber film surface. Therefore, it is preferable to sufficiently increase the optical contrast of the reflected EUV light by utilizing the principle of phase shift in relation to the reflected light from the multilayer reflective film.

[0058] In order to utilize the principle of phase shift in relation to the reflected light from the multilayer reflective film, it is preferable that the phase of the EUV reflected light from the absorber film differs from the phase of the EUV reflected light from the multilayer reflective film by 175 to 185 degrees. In order to sufficiently increase the optical contrast of the EUV reflected light, the phase difference between the EUV reflected light from the absorber film and the EUV reflected light from the multilayer reflective film is preferably 175 to 185 degrees, and more preferably 177 to 183 degrees.

[0059] The absorber film is made of a material with a high absorption coefficient for EUV light. As a material with a high absorption coefficient for EUV light, it is preferable to use a material mainly composed of tantalum (Ta). Here, the material mainly composed of tantalum (Ta) may be a material containing 40 at% (atomic composition ratio %) or more of Ta. It is preferable that the absorber film contains tantalum (Ta) at preferably 50 at% or more, more preferably 55 at% or more.

[0060] The material containing Ta as a main component for use in the absorber film contains at least one component selected from the group consisting of hafnium (Hf), silicon (Si), zirconium (Zr), germanium (Ge), boron (B), hydrogen (H) and nitrogen (N) in addition to Ta. Specific examples of materials containing the above elements other than Ta include TaN, TaNH, TaHf, TaHfN, TaBSi, TaBSiN, TaB, TaBN, TaSi, TaSiN, TaGe, TaGeN, TaZr, and TaZrN.

[0061] The absorber film preferably does not contain oxygen (O). The content of O in the absorber film is preferably less than 25 at %. The content of oxygen in the absorber film is preferably 15 at % or less, more preferably 10 at % or less, and further preferably 5 at % or less. The thickness of the absorber film may be sufficient to sufficiently absorb the exposure light, for example, EUV light, and is preferably about 1 nm to 100 nm, or 1 nm to 60 nm, and more preferably 3 nm to 56 nm.

[0062] The hard mask layer 16, together with the resist layer 17, acts as a mask in the patterning of the absorber layer 15 and other layers. Specifically, the hard mask layer 16 is patterned using the resist layer 17 as a mask to form a hard mask pattern 16p. The hard mask pattern 16p acts as a mask in the patterning of the absorber layer 15 and other layers.

[0063] For this reason, the hard mask layer 16 is formed from a material that can act as a mask in patterning the absorber layer 15, etc. The hard mask layer 16 is made of a material that is resistant to an etchant used in etching the absorber layer 15. Specifically, the hard mask layer 16 contains chromium (Cr). In addition, the hard mask layer 16 has a composition other than chromium, such as oxygen and carbon, with a content of 10 atm % or less, more preferably 5 atm % or less.

[0064] In this case, the thickness of the hard mask layer 16 may be in the range of 1 to 20 nm, and is preferably in the range of about 1 to 10 nm, or 3 to 5 nm. The hard mask layer 16 can be formed on the absorber layer 15 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0065] Moreover, the hard mask layer 16 may contain Ti instead of chromium (Cr). In this case, the content of oxygen, carbon, etc. as impurities is set to 10 atm % or less, more preferably, the content of oxygen, carbon, etc. is set to 5 atm % or less.

[0066] In this case, the thickness of the hard mask layer 16 may be in the range of 1 to 20 nm, and is preferably in the range of about 1 to 10 nm, or 3 to 5 nm. The hard mask layer 16 can be formed on the absorber layer 15 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0067] In the mask blank 10 for patterning evaluation according to this embodiment, a film corresponding to a thermal diffusion suppressing film can also be provided between the false reflective layer 12 and the protective layer 13 . In a reflective mask blank, the thermal diffusion suppression film can be made of a material having a refractive index (n) greater than 0.90 and an extinction coefficient (k) smaller than −0.020.

[0068] Here, a thermal diffusion suppression film is provided between the protective film made of ruthenium or a ruthenium compound and the multilayer reflective film. This can suitably suppress the formation of a diffusion layer between the protective film and the Si film of the top layer of the multilayer reflective film during the formation of the protective film or during subsequent heat treatments (heat treatments for reducing the stress of the multilayer reflective film, pre-baking of the resist film, exposure, cleaning, etc.). Therefore, no reduction in reflectance occurs due to the diffusion layer. Furthermore, by providing the thermal diffusion suppression film between the protective film and the multilayer reflective film, a higher reflectance can be obtained, and the optical characteristics (reflectance) can be improved.

[0069] The thermal diffusion suppression film may be composed of at least one metal selected from molybdenum (Mo), niobium (Nb), zirconium (Zr), yttrium (Y), titanium (Ti), and lanthanum (La), or a compound containing at least one selected from molybdenum (Mo), niobium (Nb), zirconium (Zr), yttrium (Y), titanium (Ti), and lanthanum (La) and at least one selected from oxygen (O), boron (B), nitrogen (N), carbon (C), and silicon (Si).

[0070] Alternatively, the thermal diffusion suppression film may be made of carbon (C) or a compound containing carbon (C) and at least one selected from oxygen (O), boron (B), nitrogen (N) and silicon (Si). The thermal diffusion suppressing film may be made of a compound containing at least one element selected from oxygen (O), boron (B), nitrogen (N) and silicon (Si).

[0071] The thermal diffusion suppression film may have a thickness of 0.5 to 2.5 nm. The thermal diffusion suppressing film can be formed on the absorber layer 15 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0072] The resist layer 17 may be an electron beam resist. Specifically, the resist layer 17 may be a polystyrene resin derivative. The resist layer 17 made of an electron beam resist is formed by coating. The resist layer 17 may be baked. In this case, the thickness of the resist layer 17 may be in the range of 1 to 20 nm, and is preferably in the range of about 1 to 10 nm, or 3 to 10 nm. Alternatively, the total thickness of the resist layer 17 and the hard mask layer 16 can be set to 40 nm to 100 nm.

[0073] Next, an evaluation process using the patterning evaluation mask blank 10 according to this embodiment will be described. FIG. 2 is a cross-sectional view showing a method for evaluating drawing using a mask blank for drawing evaluation in this embodiment.

[0074] The materials and formation methods of each layer of the patterning evaluation mask blank 10 according to this embodiment are as described above. 2, a predetermined transfer pattern is formed on the absorber layer 15 of this patterning evaluation mask blank 10. First, patterning is performed on the resist layer 17 formed on the absorber layer 15 using an electron beam patterning machine, and the patterned resist pattern 17p is formed by developing the patterned resist layer 17p.

[0075] Using the formed resist pattern 17p as a mask, the hard mask layer 16 is dry etched to form a hard mask pattern 16p having a predetermined transfer pattern. When the hard mask layer 16 is made of a material mainly composed of Cr, dry etching using a chlorine-based gas or a fluorine-based gas can be used. When the hard mask layer 16 is made of a Cr-based material, dry etching using a mixed gas containing chlorine and oxygen can be used.

[0076] The absorber layer 15 is dry-etched using the formed resist pattern 17p and hard mask pattern 16p as a mask to form an absorber layer pattern 15p having a predetermined transfer pattern. When the absorber layer 15 is made of a material mainly composed of Ta, dry etching using a chlorine-based gas or a fluorine-based gas can be used.

[0077] Using the formed resist pattern 17p and hard mask pattern 16p as a mask, the buffer layer 14 is dry-etched to form a buffer layer pattern 14p having a predetermined transfer pattern. When the buffer layer 14 is made of a material mainly composed of Ta, dry etching using a chlorine-based gas or a fluorine-based gas can be used.

[0078] The resist pattern 17p remaining on the absorber layer pattern 15p is removed using hot concentrated sulfuric acid or the like to produce a false mask 10p.

[0079] Here, as a drawing evaluation, a CD-SEM is used to check whether the absorber layer pattern 15p is formed as designed. Here, pattern dimension evaluation using EUV diffracted light is possible due to the large difference in reflectance between the absorber layer and the laminated reflective layer. For this reason, conventional CD-SEM evaluation is used to evaluate the false reflective layer.

[0080] Moreover, as a drawing evaluation, an inspection is performed by CD-SEM to check whether the hard mask pattern 16p is formed as designed.

[0081] Furthermore, an evaluation is performed with respect to the adhesion between the resist layer 17 and the hard mask layer 16. In this case, a method can be used in which the resist after writing and development is observed with an SEM to evaluate whether there is any pattern disappearance or collapse.

[0082] In addition, the behavior of the resist layer 17 with respect to the electron beam when EB exposure is performed is evaluated. In this case, a method can be used in which drawing and development are performed using the proximity effect correction of EB exposure used in a normal laminated reflective film, the pattern dimensions of the hard mask pattern 16p are measured, and the difference from the design value is compared.

[0083] In addition, the behavior of the hard mask layer 16 against the electron beam when EB exposure is performed is evaluated. In this case, after drawing, developing, and etching the hard mask using the proximity effect correction of EB exposure used in a normal laminated reflective film, the dimensions of the formed hard mask pattern 16p are measured and compared with the design values.

[0084] Using the formed hard mask pattern 16p as a mask, the buffer layer 14 is dry-etched to form a buffer layer pattern 14p having a predetermined transfer pattern. When the buffer layer 14 is made of a material mainly composed of Ru, dry etching using a chlorine-based gas or a fluorine-based gas can be used.

[0085] In addition, it is also possible not to form the buffer layer pattern 14p. In the case of performing drawing evaluation in the manufacture of a reflective mask that can obtain the required reflectance without removing the buffer layer 14, the buffer layer 14 can be left on the pseudo-reflective layer 12 with the protective layer without processing it into a pattern similar to that of the absorber layer 15. The hard mask pattern 16p may be removed. In the case of the hard mask layer 16 made of a Cr-based material, dry etching with a mixed gas containing chlorine and oxygen can be used.

[0086] In the mask blank 10 for drawing evaluation according to this embodiment, since a multilayer reflective film is not formed, the drawing performance of the reflective mask blank used in EUV lithography can be evaluated with the same accuracy and precision without using the reflective mask blank used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, as the drawing characteristic, the adhesion between the resist layer 17 and the hard mask layer 16 formed when forming a pattern from the mask blank as a mask can be evaluated.

[0087] In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography.

[0088] Furthermore, in the mask blanks 10 for patterning evaluation in this embodiment, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks 10 for patterning evaluation in this embodiment, the manufacturing process is simplified and the mask blanks 10 can be easily manufactured, and the manufacturing time and manufacturing cost can be reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0089] In this embodiment, as long as it is possible to perform drawing evaluation, it is not limited to the above-mentioned configuration. For example, in the layer configuration of the reflective mask blank, as long as the false reflective layer 12 is a single layer film formed of the same elements as the multilayer reflective film and is a layer configuration required for drawing evaluation, other film configurations are also possible. Also, the resist layer 17 may not be formed.

[0090] Hereinafter, a second embodiment of a mask blank for patterning evaluation according to the present invention will be described with reference to the drawings. 3 is a cross-sectional view showing a mask blank for patterning evaluation in this embodiment, in which reference numeral 10 denotes the mask blank for patterning evaluation.

[0091] The mask blank 10 for writing evaluation according to this embodiment is a pseudo mask blank for evaluating writing performance. That is, the writing performance is evaluated when performing patterning in the mask blank, that is, a writing process performed when manufacturing a mask from the mask blank.

[0092] In particular, the drawing evaluation mask blank 10 according to this embodiment is used for evaluation in lithography using extreme ultraviolet light (EUV) having a wavelength of about 0.2 to 100 nm, preferably about 13.5 nm, as exposure light.

[0093] The mask blanks 10 for pattern evaluation according to this embodiment are used for UEV reflective mask blanks. That is, the mask blanks 10 for pattern evaluation according to this embodiment are not actually used as a mask, and do not need to have a reflectivity with respect to the above-mentioned exposure light.

[0094] As shown in FIG. 1, the mask blank 10 for drawing evaluation according to this embodiment has a substrate 11, a false reflective layer 12 formed on the substrate 11, a hard mask layer 16 formed on the false reflective layer 12, and a resist layer 17 formed on the hard mask layer 16.

[0095] The substrate 11 is a quartz substrate (glass substrate). The glass substrate is made of a material having excellent resistance to UEV irradiation, such as a quartz glass substrate. The size of the substrate 11 is not particularly limited and is appropriately selected according to the substrate to be exposed using the lithography (semiconductor substrate, substrate for FPD such as LCD (liquid crystal display), plasma display, organic EL (electroluminescence) display, etc.).

[0096] In this embodiment, a rectangular substrate with sides of about 100 mm to 2000 mm or more and a thickness of about 1 mm can be used as the substrate 11. The substrate 11 can have a surface condition equivalent to that of an EUV mask blank, for example, a smooth surface of 0.15 nm rms or less, preferably 0.1 nm rms or less, and a flatness of 100 nm or less, preferably 70 nm or less.

[0097] In the mask blank 10 for patterning evaluation according to this embodiment, when quartz glass is used as the substrate 11, it can have the same characteristics as a mask blank used with exposure light having a longer wavelength. This allows the substrate procurement cost and the work procedures such as surface treatment in the pre-processing of the substrate to be the same as in the past, and makes it easier to handle the substrate.

[0098] Since the substrate 11 according to this embodiment is applicable to the evaluation of reflective mask blanks, transparency is not important. The substrate 11 according to this embodiment may be made of zero expansion glass, similar to reflective mask blanks using UEV. Here, the zero expansion glass is selected from those that are not significantly affected by thermal expansion during lithography even when the temperature rises due to UEV irradiation.

[0099] Specifically, the substrate 11 has a low thermal expansion coefficient (0±1.0×10 -7 / °C, more preferably 0±0.3×10 -7 / °C, and more preferably 0±0.2×10 -7 / °C, and more preferably 0±0.1×10 -7 / °C, and 0±0.05×10 is particularly preferable. -7 / ° C. In addition, it is preferable that the surface has excellent smoothness, flatness, and resistance to a cleaning solution used for cleaning a mask blank or an EUV mask after forming a mask pattern.

[0100] Specifically, the substrate 11 may be made of glass having a low thermal expansion coefficient, such as SiO2-TiO2 glass, but is not limited thereto. Substrates may also be made of crystallized glass in which β-quartz solid solution is precipitated, quartz glass, silicon, metal, etc. A film such as a stress compensation film may also be formed on the substrate. An example of a metal substrate is an Invar alloy (Fe-Ni alloy).

[0101] The substrate 11 is preferably a substrate having high smoothness and flatness. In particular, it is preferable that the substrate has a smooth surface of 0.2 nmRms or less (smoothness in a 10 μm square area) and a flatness of 100 nm or less (flatness in a 142 mm square area). In addition, the substrate 11 is preferably one having high rigidity to prevent deformation due to film stress of the film formed thereon. In particular, it is preferable that the substrate has a high Young's modulus of 65 GPa or more.

[0102] The unit of smoothness, Rms, is the root-mean-square roughness, which can be measured with an atomic force microscope. Flatness is a value that indicates the surface warpage (amount of deformation) indicated by TIR (Total Indicated Reading), and is the absolute value of the difference in height between the highest point on the substrate surface above the focal plane, which is determined by the least squares method with the substrate surface as the reference plane, and the lowest point on the substrate surface below the focal plane.

[0103] The false reflective layer 12 is a single layer film containing the same elements as the multilayer reflective film of the EUV mask blanks as the patterning evaluation mask blanks 10. The multilayer reflective film of the EUV mask blanks is a kind of Bragg reflection mirror for EUV light.

[0104] That is, the pseudo-reflective layer 12 can be a single layer film made of the same combination of elements as the multilayer reflective film, such as Mo / Si, Ru / Si, Mo / Be, Rh / Si, Pt / Si, Mo compound / Si compound, Si / Mo / Ru, Si / Mo / Ru / Mo, Si / Ru / Mo / Ru, etc. The pseudo-reflective layer 12 can be a single layer film containing molybdenum and silicon. This is because by using a film containing the same elements as the multilayer reflective film, the amount and range of backscattering of the electron beam during EB exposure in the drawing performance evaluation can be made equivalent to that of the multilayer reflective film, thereby meeting the condition of minimizing the influence of proximity effect correction.

[0105] Here, the pseudo-reflective layer 12 is preferably a single-layer film containing the same elements as the multi-layer reflective film, so for example, in the case of Mo / Si, it is preferable that it does not contain impurities other than molybdenum and silicon. Specifically, it is preferable that the concentration of impurities other than molybdenum and silicon is 20 ppm or less (other than oxygen and carbon).

[0106] The thickness of the false reflective layer 12 can be 10 nm to 50 nm, and more preferably 25 nm to 35 nm. This is because the hard mask layer 16 is thin, so the evaluation accuracy of the pattern dimension of the hard mask layer 16 itself by CD-SEM is low, and the patterned hard mask layer 16 may be used to etch the false reflective layer 12 to evaluate the pattern dimension, so the condition of keeping the thickness ratio defined by the etching selectivity between the hard mask layer 16 and the false reflective layer 12 constant is satisfied. Therefore, if the thickness is smaller than the above range, it is not preferable because there is a problem that the evaluation accuracy by CD-SEM decreases, and if the thickness is larger than the above range, it is not preferable because there is a problem that the hard mask layer 16 disappears before the end point, causing deterioration of the pattern shape.

[0107] The single layer false reflective layer 12 can be formed on the substrate 11 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0108] The single layer of the false reflective layer 12 may have a composition gradient in the thickness direction. For example, the composition gradient may be such that the Si concentration increases toward the top surface of the false reflective layer 12, that is, the direction farthest from the substrate 11.

[0109] The hard mask layer 16, together with the resist layer 17, acts as a mask in the patterning of an absorber film or the like in the EUV reflective mask blanks. Specifically, the hard mask layer 16 is patterned using the resist layer 17 as a mask to form a hard mask pattern 16p. The hard mask pattern 16p acts as a mask in the patterning of the absorber film and the like.

[0110] For this reason, the hard mask layer 16 is made of a material that can act as a mask in patterning the absorber film, etc., of the EUV reflective mask blanks. The hard mask layer 16 is made of a material that is resistant to an etchant used in etching the absorber film, etc., of the EUV reflective mask blanks. Specifically, the hard mask layer 16 contains chromium (Cr). In addition, the hard mask layer 16 has a composition other than chromium, such as oxygen and carbon, with a content of 10 atm % or less, more preferably, a content of 5 atm % or less of oxygen, nitrogen, carbon, etc.

[0111] In this case, the thickness of the hard mask layer 16 may be in the range of 1 to 20 nm, and is preferably in the range of about 1 to 10 nm, or 3 to 5 nm. The hard mask layer 16 can be formed on the false reflective layer 12 by a sputtering method such as ion beam sputtering in addition to DC sputtering and RF sputtering.

[0112] Moreover, the hard mask layer 16 may contain Ti instead of chromium (Cr). In this case, the content of oxygen, nitrogen, carbon, etc. as impurities is set to 10 atm % or less, more preferably, the content of oxygen, nitrogen, carbon, etc. is set to 5 atm % or less.

[0113] In this case, the thickness of the hard mask layer 16 may be in the range of 1 to 20 nm, and is preferably in the range of about 1 to 10 nm, or 3 to 5 nm. The hard mask layer 16 can be formed on the absorber layer 15 by a sputtering method such as ion beam sputtering, in addition to DC sputtering and RF sputtering.

[0114] The resist layer 17 may be an electron beam resist. Specifically, the resist layer 17 may be a polystyrene resin derivative. The resist layer 17 made of an electron beam resist is formed by coating. The resist layer 17 may be baked. In this case, the thickness of the resist layer 17 may be in the range of 20 to 60 nm, and preferably in the range of 40 to 50 nm.

[0115] Next, an evaluation process using the patterning evaluation mask blank 10 according to this embodiment will be described. FIG. 4 is a cross-sectional view showing a patterning evaluation step using a mask blank for patterning evaluation in this embodiment.

[0116] The materials and formation methods of each layer of the patterning evaluation mask blank 10 according to this embodiment are as described above. Then, as shown in FIG. 4, a pattern is drawn on the resist layer 17 formed on the hard mask layer 16 using an electron beam drawing machine, and then developed to form a predetermined resist pattern 17p.

[0117] Using the formed resist pattern 17p as a mask, the hard mask layer 16 is dry etched to form a hard mask pattern 16p having a predetermined transfer pattern. When the hard mask layer 16 is made of a material mainly composed of Cr, dry etching using a chlorine-based gas or a fluorine-based gas can be used. When the hard mask layer 16 is made of a Cr-based material, dry etching using a mixed gas containing chlorine and oxygen can be used. The etching of the hard mask layer 16 can be performed in accordance with the etching of an absorption band film or the like that is to be patterned in an EUV reflective mask blank.

[0118] The resist pattern 17p remaining on the hard mask pattern 16p is removed using hot concentrated sulfuric acid or the like to produce a false mask 10p.

[0119] Here, as a drawing evaluation, an inspection is performed to check whether the hard mask pattern 16p is formed as designed. The inspection of the hard mask pattern 16p is performed by, for example, using a CD-SEM to detect the shape of the hard mask pattern 16p, and the result is evaluated.

[0120] Also, an evaluation is made of the adhesion between the resist layer 17 and the hard mask layer 16. In this case, a method can be used in which the resist after writing and development is observed with an SEM to evaluate whether there is any pattern disappearance or collapse.

[0121] In addition, the behavior of the resist layer 17 with respect to the electron beam when EB exposure is performed is evaluated. In this case, a method can be used in which the pattern dimensions of the resist after writing and development are measured using the proximity effect correction of EB exposure used in a normal laminated reflective film, and the difference from the design value is compared.

[0122] In the mask blank 10 for drawing evaluation according to this embodiment, since it has the minimum configuration required for drawing evaluation without forming a multilayer reflective film, it is possible to evaluate the drawing performance for a reflective mask blank used in EUV lithography with the same accuracy and precision without using a reflective mask blank used in EUV lithography, which has a complex structure and requires extremely strict manufacturing conditions. Specifically, as the drawing characteristic, it is possible to evaluate the adhesion between the resist layer 17 and the hard mask layer 16 formed when forming a pattern from the mask blank as a mask.

[0123] In addition, in terms of drawing characteristics, it is possible to evaluate whether the spread and amount of backscattered electrons relative to the incident electron beam when performing EB exposure are equivalent to those of reflective mask blanks used in actual EUV lithography.

[0124] Furthermore, in the mask blanks 10 for patterning evaluation in this embodiment, a multilayer reflective film, which is difficult to form, is not formed when the defect specifications are satisfied. Therefore, in the mask blanks 10 for patterning evaluation in this embodiment, the manufacturing process is simplified and the mask blanks 10 can be easily manufactured, and the manufacturing time and manufacturing cost can be reduced, and the patterning characteristics can be easily evaluated, compared to the reflective mask blanks used in EUV lithography.

[0125] In this embodiment, as long as it is possible to perform drawing evaluation, it is not limited to the above-mentioned configuration. For example, in the layer configuration of the reflective mask blank, as long as the false reflective layer 12 is a single layer film formed of the same elements as the multilayer reflective film and is a layer configuration required for drawing evaluation, other film configurations are also possible. EXAMPLES

[0126] Hereinafter, an embodiment of the present invention will be described.

[0127] As a specific example of the present invention, an evaluation test of the lithography characteristics of a mask blank for lithography evaluation will be described.

[0128] <Experimental Example 1> The substrate used is a quartz glass substrate (152 mm square, 6.3 mm thick). The thermal expansion coefficient of this substrate is 0.2×10 -7 / °C and Young's modulus is 67 GPa. The glass substrate was mechanically polished to a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less.

[0129] The false reflective layer formed on the substrate was a single layer of MoSi2. That is, the false reflective layer was formed on the substrate by DC magnetron sputtering using a MoSi target. The MoSi2 film was deposited to a thickness of 20 nm, and finally, a Ru film was deposited to a thickness of 5 nm as a protective layer using a Ru target.

[0130] Furthermore, a material containing Ta, B, and N was formed on the Ru film to a thickness of 30 nm as an absorber layer. Here, using a target containing Ta and B, 10% nitrogen (N2) was added to argon (Ar) and the film was formed by DC magnetron sputtering. The composition ratio of the formed TaBN film was 0.8 at% Ta, 0.1 at% B, and 0.1 at% N.

[0131] Furthermore, a material containing Ta, B, and O was formed to a thickness of 13 nm as an absorber layer. Here, a target containing Ta and B was used, and the film was formed by DC magnetron sputtering with argon (Ar) and 10% nitrogen (O2). The composition ratio of the formed TaBO film was 0.8 at% Ta, 0.1 at% B, and 0.1 at% O.

[0132] Furthermore, a Cr single layer film was formed as a hard mask layer on the Ta-containing film, and a resist for electron beam lithography was formed thereon as a resist layer.

[0133] Next, the writing performance was evaluated when fabricating a reflective mask for EUV exposure from the reflective mask blank using this mask blank for writing evaluation. Here, the writing performance was evaluated under the same conditions as those for forming a pattern for a 16 Gbit-DRAM with a design rule of 0.07 μm.

[0134] First, a resist pattern was formed on the resist layer on the mask blank for patterning evaluation by electron beam patterning and development. Using this resist pattern as a mask, the hard mask layer was dry etched with chlorine gas to form a hard mask pattern. Using this resist pattern and the hard mask pattern as a mask, the absorber layer was dry etched with chlorine gas to form an absorber layer pattern. Furthermore, the buffer layer remaining in the area where there was no absorber layer pattern was removed by dry etching according to the absorber layer pattern using a mixed gas of chlorine and oxygen, exposing the protective layer and the false reflective layer to obtain a false mask.

[0135] Here, to evaluate the writing performance of the fake mask, an inspection is performed to check whether the hard mask pattern is formed as designed. For the inspection of the hard mask pattern, the shape of the hard mask pattern is detected by, for example, a CD-SEM, and the result is evaluated.

[0136] In addition, the adhesion between the resist layer and the hard mask layer is evaluated. In this case, the resist after writing and development is observed with an SEM to check for pattern loss or collapse.

[0137] The behavior of the resist layer against the electron beam during EB exposure is evaluated. In this case, a method can be used in which the proximity effect correction (amount and range of backscattering) of the electron beam during EB exposure is set to be the same as that during multilayer reflective film exposure, and the pattern dimensions after development are compared.

[0138] The behavior of the hard mask layer against the electron beam during EB exposure is evaluated. In this case, a method can be used in which the proximity effect correction (amount and range of backscattering) of the electron beam during EB exposure is set to the same as that during multilayer reflective film exposure, and the pattern dimensions after development and resist move are compared with the design values. Here, the specifications for the drawing evaluation test are shown as shown in FIG. The electron beam proximity effect correction parameters (backscattering amount and range) during EB exposure were set to the same settings as those for multilayer reflective film exposure, and the pattern dimensions formed by etching the hard mask were evaluated using CD-SEM. The difference was -6 nm when the design CD was 60 nm.

[0139] From this result, it is understood that the mask blank for drawing evaluation formed with this film configuration can be used for drawing verification. [Explanation of symbols]

[0140] 10...Mask blanks for pattern evaluation 11...Substrate 12...false reflective layer 13…Protective layer 14…Buffer layer 15...Absorbent layer 16…Hard mask layer 17...Resist layer

Claims

1. A mask blank for evaluating the writing performance of a reflective mask blank used in EUV lithography, comprising: A substrate; a false reflective layer laminated to the substrate; a hard mask layer laminated to the false reflective layer; having The false reflective layer is a single layer film made of a material equivalent to a multilayer reflective film for EUV, The hard mask layer is a layer equivalent to a layer that serves as a mask for an absorber layer against EUV, The thickness of the false reflection layer is 10 nm to 100 nm; The hard mask layer and the false reflective layer are set to a thickness ratio that allows evaluation of a pattern dimension in patterning of the false reflective layer using the hard mask layer as a mask. A mask blank for pattern evaluation, comprising:

2. A resist layer is laminated on the hard mask layer.

2. The mask blank for patterning evaluation according to claim 1.

3. The false reflective layer contains molybdenum and silicon, and the concentration of impurities other than oxygen and carbon is 20 ppm or less; 2. The mask blank for patterning evaluation according to claim 1.

4. The hard mask layer contains chromium and has a thickness of 1 nm to 20 nm.

2. The mask blank for patterning evaluation according to claim 1.

5. an absorber layer laminated to the false reflective layer; The hard mask layer is laminated to the absorber layer.

3. The mask blank for patterning evaluation according to claim 2.

6. a protective layer laminated to the false reflective layer; The absorbent layer is laminated on the protective layer.

6. The mask blank for patterning evaluation according to claim 5.

7. A buffer layer is laminated on the protective layer, The absorber layer is laminated on the buffer layer.

7. The mask blank for patterning evaluation according to claim 6.

8. The substrate is a quartz substrate, or the substrate is a zero expansion substrate; 8. The mask blank for patterning evaluation according to claim 1 .

9. Using the mask blank for patterning evaluation according to any one of claims 2, 5 to 7, forming a resist pattern by performing writing and development using an electron beam writing device, or by etching the hard mask layer to form a pattern, and then removing the resist layer, measuring the pattern dimensions using a CD-SEM to evaluate the writing characteristics; A drawing evaluation method comprising:

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