Reflective mask blank and reflective mask

Abstract

The purpose of the present invention is to provide an EUV photomask blank and an EUV photomask which have high resistance to hydrogen radicals, low EUV reflectance, and a high OD value. A reflective mask blank (10) according to an embodiment of the present invention is provided with at least a substrate (1), a multilayer reflective film (2), a cover layer (3), and a low-reflection part (5) in which a first absorption film (51) having high hydrogen radical resistance and a second absorption film (52) having high hydrogen radical resistance are alternately laminated. The extinction coefficient of the first absorption film (51) is different from the extinction coefficient of the second absorption film (52), or the refractive index of the first absorption film (51) is different from the refractive index of the second absorption film (52), and the extinction coefficient of the second absorption film (52) with respect to EUV light is 0.04 or more.

Description

Technical Field

[0001] The present invention relates to a reflective mask blank and a reflective mask used in the manufacture of semiconductor devices and the like. Background Technology

[0002] In semiconductor device manufacturing processes, as semiconductor devices become increasingly miniaturized, the requirements for miniaturization in photolithography technology also increase. In photolithography, the minimum developing size of the transferred pattern is highly dependent on the wavelength of the exposure light source; the shorter the wavelength, the smaller the minimum resolution size can be. Therefore, in semiconductor device manufacturing processes, the exposure light source has been replaced from the previous 193nm ArF excimer laser to a 13.5nm EUV exposure light source.

[0003] Because EUV light has a short wavelength, most materials have high light absorption. Therefore, the photomask used for EUV (EUV mask) is a reflective mask, unlike conventional transmissive masks (see, for example, Patent Document 1 and Patent Document 2). Patent Document 1 discloses the following technique: In a reflective exposure mask used in EUV lithography, a multilayer film is formed on a substrate by periodically stacking two or more material layers, and a mask pattern composed of a nitrogen-containing metal film or a stacked structure of metal nitride films and metal films is formed on the multilayer film.

[0004] Furthermore, Patent Document 2 discloses a reflective EUV mask that uses a phase control film as an absorber film on a multilayer reflective film, and employs a stacked structure of alternating layers of high-refractive-index material and low-refractive-index material on the phase control film.

[0005] As mentioned above, EUV lithography cannot use refractive optical systems that utilize the transmission of light; therefore, the optical system components of the exposure machine are not lenses, but mirrors. Consequently, there is a problem that the incident light incident on the EUV photomask and the reflected light reflected at the EUV photomask cannot be designed to be coaxial. Typically, in EUV lithography, the following method is used: EUV light is incident with its optical axis tilted 6 degrees from the vertical direction of the EUV photomask, and the reflected light, reflected at a negative 6-degree angle, illuminates the semiconductor substrate.

[0006] Thus, in EUV lithography, due to the tilt of the optical axis, the EUV light incident on the EUV photomask will produce shadows on the pattern (absorption layer pattern) of the EUV photomask, which can sometimes lead to a problem known as the "projection effect (shadowing effect)" that degrades the transfer performance.

[0007] To address this issue, Patent Document 1 discloses the following method: by making the extinction coefficient k for EUV 0.03 or higher, the thickness of the absorber layer can be made thinner than before (less than 60 nm), thereby reducing the projection effect.

[0008] Furthermore, Patent Document 2 discloses a method in which the reflectivity of EUV light is reduced to less than 2% by alternately stacking layers of high-refractive-index material and low-refractive-index material as an absorption film, with a film thickness of thinner absorber layer than before.

[0009] Furthermore, in current EUV exposure apparatuses, cleaning using hydrogen radicals is performed to prevent contamination within the chamber caused by pollutants. Since photomasks are exposed to a hydrogen radical environment, low resistance to hydrogen radicals can sometimes shorten their lifespan. Therefore, photomasks need to be formed from compound materials with high resistance to hydrogen radicals.

[0010] However, neither Patent Document 1 nor Patent Document 2 mentions hydrogen radical resistance, nor does it specify whether the photomask can withstand long-term use.

[0011] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 6408790 Patent Document 2: Japanese Patent No. 6661724 Summary of the Invention

[0012] Technical issues Thus, in the reflective mask blanks and reflective masks according to the prior art, there are no reflective mask blanks and reflective masks that minimize the projection effect, reduce the reflectivity of EUV (increase the absorption rate), and improve the resistance to hydrogen radicals.

[0013] Therefore, the object of the present invention is to provide a reflective mask preform (EUV photomask preform) and a reflective mask (EUV photomask) that exhibit high resistance to hydrogen radicals and excellent transferability by minimizing the projection effect. In other words, the object of the present invention is to provide an EUV photomask preform (reflective mask preform) and an EUV photomask (reflective mask) that exhibit high resistance to hydrogen radicals, low EUV reflectivity, and high OD value.

[0014] Technical solution According to one aspect of the present invention, a reflective mask preform is used for manufacturing a reflective mask for pattern transfer using extreme ultraviolet light as a light source, comprising at least: a substrate; a multilayer film formed on the substrate; a cover film formed on the multilayer film and protecting the multilayer film; and an absorbent film formed on the cover film, wherein the absorbent film is formed by alternating layers of a first absorbent film and a second absorbent film, the first absorbent film having high hydrogen radical resistance, the extinction coefficient of the first absorbent film being different from the extinction coefficient of the second absorbent film, or the refractive index of the first absorbent film being different from the refractive index of the second absorbent film, and the extinction coefficient of the second absorbent film for EUV light being 0.04 or more.

[0015] According to one aspect of the present invention, a reflective mask comprises at least: a substrate; a multilayer film formed on the substrate; a cover film formed on the multilayer film and protecting the multilayer film; and an absorber film formed on the cover film and patterned thereon, the absorber film being formed by alternating layers of a first absorber film and a second absorber film, the first absorber film having high hydrogen radical resistance, the extinction coefficient of the first absorber film being different from the extinction coefficient of the second absorber film, or the refractive index of the first absorber film being different from the refractive index of the second absorber film, and the extinction coefficient of the second absorber film for EUV light being 0.04 or more.

[0016] Technical effect According to one aspect of the present invention, by alternately stacking a first absorption film having high resistance to hydrogen radicals and a second absorption film having an extinction coefficient of 0.04 or higher for EUV as the absorption film, it is possible to provide EUV photomask preforms (reflective mask preforms) and EUV photomasks (reflective masks) that have high resistance to hydrogen radicals and excellent transferability by minimizing projection effects. More specifically, according to one aspect of the present invention, by alternately stacking a first absorption film having high resistance to hydrogen radicals and a second absorption film having an extinction coefficient of 0.04 or higher for EUV as the absorption film, it is possible to provide EUV photomask preforms (reflective mask preforms) and EUV photomasks (reflective masks) that have high resistance to hydrogen radicals, low EUV reflectivity, and high OD values. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view illustrating the structure of a reflective photomask blank according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic cross-sectional view illustrating the structure of a reflective photomask according to an embodiment of the present invention.

[0019] Figure 3 It is a chart showing the optical constants of various metals at the wavelength of EUV light.

[0020] Figure 4 This is a conceptual diagram illustrating the hydrogen radical tolerance evaluation method according to this embodiment.

[0021] Figure 5 This is a schematic cross-sectional view illustrating a modified example of a reflective photomask according to an embodiment of the present invention.

[0022] Symbol Explanation 1: Substrate (low thermal expansion film) 2: Multilayer reflective film 3: Covering layer 4: Reflective layer 5: Low-reflection section (absorption film) 5a: Low-reflectivity pattern 51: First Absorbing Membrane 52: Second Absorbent Membrane 52a: Passivation layer 6: Back conductive film 10: Reflective photomask preform (reflective photomask preform) 20: Reflective photomask (reflective mask) 300: Chamber 301: Electrode 302: Sample Detailed Implementation

[0023] An embodiment of the present invention will be described with reference to the accompanying drawings.

[0024] The structures shown in the accompanying drawings are schematic, and the relationship between thickness and planar dimensions, the proportions of thickness in each layer, etc., differ from actual structures. Furthermore, the embodiments shown below illustrate structures for embodying the technical concept of the present invention; the materials, shapes, and structures of the constituent components of the technical concept of the present invention are not limited to the following. Various modifications can be made to the technical concept of the present invention within the scope of the claims as defined in the claims.

[0025] (Structure of a reflective photomask) use Figure 1 and Figure 2 The basic structures of the reflective photomask blank (reflective photomask blank) and the reflective photomask (reflective photomask) according to embodiments of the present invention will be described.

[0026] Figure 1 This is a schematic cross-sectional view showing the reflective photomask blank 10 according to an embodiment of the present invention. Furthermore, Figure 2 This is a schematic cross-sectional view showing a reflective photomask 20 according to an embodiment of the present invention. Figure 2 The reflective photomask 20 shown according to an embodiment of the present invention is a... Figure 1 The reflective layer 4 of the reflective photomask blank 10 shown in the present invention is formed by patterning.

[0027] According to an embodiment of the present invention, the reflective photomask blank 10 is a reflective photomask blank for manufacturing a reflective photomask for pattern transfer using extreme ultraviolet light source, and it includes at least: a substrate (low thermal expansion film) 1; a multilayer reflective film (multilayer film) 2 formed on the substrate 1; a cover film (covering layer) 3 formed on the multilayer reflective film 2 to protect the multilayer reflective film 2; and a low reflectivity portion (absorption film) 5 formed on the cover film 3.

[0028] The low-reflection portion 5 is a laminate formed by alternately stacking a first absorption film 51 and a second absorption film 52. Furthermore, the first absorption film 51 is a layer formed of a material with high hydrogen radical resistance. Additionally, the extinction coefficient of the first absorption film 51 is different from that of the second absorption film 52, or the refractive index of the first absorption film 51 is different from that of the second absorption film 52. Moreover, the extinction coefficient of the second absorption film 52 for EUV light is 0.04 or higher.

[0029] The following provides a detailed description of the structures of the reflective photomask blank 10 and the reflective photomask 20.

[0030] like Figure 1 As shown, the reflective photomask blank 10 according to an embodiment of the present invention has a multilayer reflective film 2 on a substrate 1, and a cover layer 3 on the multilayer reflective film 2. Thus, a reflective layer 4 having the multilayer reflective film 2 and the cover layer 3 is formed on the substrate 1.

[0031] Furthermore, a low-reflection portion 5 is provided on the reflective layer 4. The low-reflection portion 5 is, for example, a laminate consisting of four or more layers, which alternately provides a first absorption film 51 with high hydrogen radical resistance as the first layer and a second absorption film 52 with an extinction coefficient of 0.04 or higher as the second layer.

[0032] (Substrate) The substrate 1 according to an embodiment of the present invention can be a flat silicon (Si) substrate, a synthetic quartz substrate, or the like. Furthermore, low-thermal-expansion glass with added titanium can be used, but the present invention is not limited to any material with a low coefficient of thermal expansion.

[0033] (Multilayer reflective film) The multilayer reflective film 2 according to an embodiment of the present invention reflects EUV light (extreme ultraviolet light) as exposure light, and is composed of a multilayer film formed by a combination of materials with significantly different refractive indices for EUV light. For example, the multilayer reflective film 2 can be formed by repeatedly stacking layers of combinations such as molybdenum (Mo) and silicon (Si), or molybdenum (Mo) and beryllium (Be) for about 40 cycles.

[0034] (Covering layer) According to an embodiment of the present invention, the cover layer (cover film) 3 is formed of a material resistant to dry etching during the formation of the low-reflection pattern 5a, and functions as an etching stop layer to prevent damage to the multilayer reflective film 2 during the formation of the low-reflection pattern 5a by etching. Here, depending on the material of the multilayer reflective film 2 and the etching conditions, the cover layer 3 may not be provided.

[0035] Furthermore, a back conductive film 6 can be formed on the surface of the substrate 1 where the multilayer reflective film 2 is not formed. The back conductive film 6 is a film used to fix the reflective photomask 20 using the principle of an electrostatic chuck when it is placed in the exposure machine.

[0036] (Low-reflection area) A low-reflectivity pattern 5a is formed by removing a portion of the low-reflectivity portion 5 of the reflective photomask blank 10. In EUV lithography, EUV light is incident at an angle and reflected by the reflective layer 4, but the projection effect caused by the low-reflectivity pattern 5a becoming an optical path obstacle deteriorates the transfer performance onto the wafer. This deterioration in transfer performance can be reduced by thinning the thickness of the low-reflectivity portion 5 (low-reflectivity pattern 5a) that absorbs EUV light. To thin the thickness of the low-reflectivity portion 5 (low-reflectivity pattern 5a), it can be achieved by applying a material with high absorption of EUV light, i.e., a material with a high extinction coefficient k for a wavelength of 13.5 nm, to the second absorption film 52, and applying a film with a different extinction coefficient or refractive index than the second absorption film 52 to the first absorption film 51, and then alternately stacking them.

[0037] It should be noted that in this embodiment, "high extinction coefficient k" means an extinction coefficient k of 0.04 or higher. By forming the second absorption film 52 from a compound material with an extinction coefficient k of 0.04 or higher, the thickness of the second absorption film 52 is reduced, resulting in a reduction in the thickness of the low-reflection portion 5. For example, a compound material with an extinction coefficient k of 0.04 or higher may have… Figure 3 The materials shown. As compound materials with an extinction coefficient k of 0.04 or higher (second absorption film material group), such as... Figure 3 As shown, for example, a material containing one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium and rhenium.

[0038] It should be noted that, in Figure 3 Among them, materials containing one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium are exemplified as materials with high hydrogen radical resistance (first absorber material group).

[0039] By using a material group with high hydrogen radical resistance in the material of the first absorption film 51 constituting the low-reflection portion 5 of this embodiment, the hydrogen radical resistance of the entire low-reflection portion 5 can be improved.

[0040] It should be noted that in this embodiment, "material with high hydrogen radical resistance" refers to, for example, the use of... Figure 4 The apparatus shown describes a compound material with a film loss of less than 1 nm under hydrogen radical conditions, achieved by exciting the material in a hydrogen radical environment with a hydrogen flow rate of 100 sscm, using 2.45 GHz Micro Wave Plasma (MWP), and setting the distance between electrodes 301 to 18 mm. Furthermore, "film (layer) with excellent hydrogen radical resistance" refers to a film (layer) with a film loss of less than 1 nm under the aforementioned hydrogen radical environment.

[0041] The first absorber membrane 51 preferably contains one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium. If the first absorber membrane 51 contains the above-mentioned elements, it can be endowed with excellent hydrogen radical resistance.

[0042] Furthermore, the outermost layer of the low-reflection portion 5 is preferably a first absorption film 51. If the outermost layer of the low-reflection portion 5 is a first absorption film 51, then the entire low-reflection portion 5 can be endowed with excellent hydrogen radical resistance.

[0043] The second absorption film 52 preferably contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium, and rhenium. If the second absorption film 52 contains the above-mentioned elements, the extinction coefficient k of the second absorption film 52 can be greater than 0.04, and the projection effect can be reduced.

[0044] Furthermore, if the aforementioned material with high hydrogen radical resistance is also mixed into the second absorption film 52, the hydrogen radical resistance can be further improved, which is therefore more preferable. In this case, if the extinction coefficient k of the entire low-reflection portion 5 is 0.04 or higher, there is no particular problem. Furthermore, if the extinction coefficient k of the second absorption film 52 is 0.04 or higher, there is no particular problem.

[0045] It should be noted that, in this embodiment, the extinction coefficient and refractive index of each absorption film can also be adjusted by appropriately adjusting the composition ratio of the materials constituting each absorption film.

[0046] Furthermore, when it is necessary to suppress damage caused by hydrogen free radicals on the sides of the low-reflectivity pattern 5a, passivation can also be performed. Through passivation, such as... Figure 5As shown, a passivation layer 52a with high hydrogen radical resistance can be formed on the patterned side of the second absorption film 52, which can further improve hydrogen radical resistance. For example, a material with high hydrogen radical resistance (a high hydrogen radical resistance material) constituting the first absorption film 51 can also be added to the second absorption film 52, and an oxide coating (passivation layer 52a) can be formed on the patterned side of the second absorption film 52. It should be noted that as long as the extinction coefficient k of the second absorption film 52 is 0.04 or higher, there is no particular limitation on the content of the high hydrogen radical resistance material added to the second absorption film 52.

[0047] For this thin film layer (passivation layer 52a), from the viewpoint of improving durability, it is preferable that its film thickness (specifically, the thickness from the side of the pattern) is in the range of 0.5 nm or more and 8 nm or less. From the viewpoint of improving transferability, it is even more preferable that its film thickness is in the range of 0.5 nm or more and 5 nm or less. From the viewpoint of balancing improving durability and improving transferability, it is more preferable that its film thickness is in the range of 2 nm or more and 5 nm or less.

[0048] The passivation layer 52a formed on the patterned side of the second absorption film 52 can be formed, for example, by a chemical treatment method such as SPM or APM. Other chemical solutions or gases besides those described above can also be used as treatment methods. Furthermore, the passivation layer 52a can also be an oxide film; it is acceptable to form an oxide film using the methods described above or through natural oxidation.

[0049] Furthermore, regarding the thickness of the passivation layer 52a, the second absorption film 52 near the side of the cover layer 3 may be thicker, while the second absorption film 52 near the outermost surface of the low-reflection portion 5 may be thinner.

[0050] Furthermore, regarding the thickness of the passivation layer 52a, the second absorption film 52 near the side of the cover layer 3 may be thinner, while the second absorption film 52 near the outermost surface of the low-reflection portion 5 may be thicker.

[0051] It should be noted that the thickness of the passivation layer 52a can also be adjusted by appropriately adjusting the above-mentioned processing time and the type of processing agent.

[0052] The mixing ratio of the materials forming the low-reflection portion 5 needs to be adjusted so that the total film thickness of the low-reflection portion 5 is 47 nm or less to reduce the projection effect and the OD value is 1.5 or more to maintain a contrast that allows for pattern transfer. The lower limit of the mixing ratio depends on the optical constants of the mixed materials, so it cannot be generalized. However, in order to reduce the projection effect compared with conventional films, it is desirable that the material group forming the second absorption film 52 is a compound material containing at least 50 atomic percent of non-metallic elements. Moreover, in order to transfer fine patterns, it is desirable that the contrast between the intensity of light reflected by the reflective layer 4 and the low-reflection portion 5 is high. Therefore, the OD value of the low-reflection portion 5 is more preferably 2.0 or more.

[0053] Here, the optical density (OD) value, which represents the contrast between the light intensity of the reflective layer 4 and the low-reflection part 5, will be explained. When the intensity of the reflected light from the reflective layer 4 is set to Rm and the intensity of the reflected light from the low-reflection part 5 is set to Ra, the OD value is defined by the following formula (1).

[0054] OD=-log(Ra / Rm)···Formula (1) A higher OD value results in better contrast, leading to higher transferability. In reflective photomasks, pattern transfer requires OD > 1, but to achieve higher transfer performance than previous films, an OD value of 1.5 or higher is preferred.

[0055] In this embodiment, it is desirable that the number of layers of the first absorbent membrane 51 and the second absorbent membrane 52 is 4 or more. If the number of layers is 4 or more, various combinations of materials and film thicknesses can be achieved, making thin film formation possible. Furthermore, if the number of layers is in the range of 4 or more and 40 or less, sufficient thin film formation can be achieved, and if it is in the range of 4 or more and 16 or less, more combinations of materials and film thicknesses can be achieved, which is even more preferred.

[0056] Furthermore, the refractive index of the constituent material of the first absorption film 51 is preferably in the range of 0.85 or higher and 1 or lower. It should be noted that, from the viewpoint of material combination number, it is preferable that the refractive index of the constituent material of the first absorption film 51 is different from that of the constituent material of the second absorption film 52.

[0057] It should be noted that the refractive index of the constituent material of the first absorption film 51 can be greater than or less than the refractive index of the constituent material of the second absorption film 52.

[0058] Of course, the refractive index of the material constituting the first absorption film 51 can also be the same as the refractive index of the material constituting the second absorption film 52.

[0059] Furthermore, from the perspective of the number of material combinations, it is desirable that the extinction coefficient k of the constituent material of the first absorption film 51 is different from the extinction coefficient k of the constituent material of the second absorption film 52.

[0060] It should be noted that the extinction coefficient k of the constituent material of the first absorption film 51 can be greater than or less than the extinction coefficient k of the constituent material of the second absorption film 52.

[0061] Of course, the extinction coefficient k of the constituent material of the first absorption film 51 can also be the same as the extinction coefficient k of the constituent material of the second absorption film 52.

[0062] Furthermore, the thickness of each absorption film can be 0.1 nm or more. There are no particular restrictions on the thickness of the low-reflection portion 5, as long as the total thickness of each absorption film is 47 nm or less and the OD value is 1.5 or more.

[0063] For example, the thickness of the first absorbent membrane 51 can be the same as the thickness of the second absorbent membrane 52.

[0064] In addition, the thickness of the first absorbent membrane 51 can be thinner than that of the second absorbent membrane 52.

[0065] Furthermore, the thickness of the first absorbent membrane 51 can be greater than the thickness of the second absorbent membrane 52.

[0066] Furthermore, the thickness of each absorption film can gradually decrease or gradually increase in the direction away from the covering layer 3 (towards the outermost surface of the low-reflection part 5).

[0067] [Example] The present invention will now be described in more detail by way of examples, but the present invention is not limited to any of the examples.

[0068] <Example 1> A synthetic quartz substrate with low thermal expansion is used as the substrate. On the substrate, 40 layers of silicon (Si) and molybdenum (Mo) are stacked as a multilayer reflective film. The thickness of the multilayer reflective film is 280 nm.

[0069] Next, a ruthenium (Ru) coating layer with a thickness of 2.5 nm is formed on the multilayer reflective film.

[0070] A second absorption film is formed on the capping layer using tin oxide (SnO) and tantalum (Ta). The film is formed with a thickness (single layer) of 11.4 nm. The resulting second absorption film has a refractive index n of 0.95 and an extinction coefficient k of 0.050.

[0071] Next, a first absorption film is formed on the second absorption film using tantalum oxide (TaO). The film is formed with a thickness (single layer) of 1.9 nm. The resulting first absorption film has a refractive index n of 0.96 and an extinction coefficient k of 0.027.

[0072] Next, the first and second absorption films are alternately stacked to form an absorption film with a total of 6 layers (a stack consisting of three layers of the first absorption film and three layers of the second absorption film). The total thickness of the absorption film formed in this way is 39.9 nm.

[0073] Next, on the side of the substrate where the multilayer reflective film has not been formed, a back conductive film is formed with chromium nitride (CrN) to a thickness of 100 nm.

[0074] Thus, the reflective photomask blank of Example 1 was fabricated.

[0075] It should be noted that a multi-element sputtering apparatus was used to form the various films on the substrate. The thickness of each film was controlled by the sputtering time.

[0076] Next, a positive chemical amplification resist (SEBP9012: manufactured by Shin-Etsu Chemical Industry Co., Ltd.) is spin-coated onto the absorber film to form a film with a thickness of 120 nm, and then baked at 110 degrees for 10 minutes to form a resist film.

[0077] Next, the predetermined pattern is drawn on the positive chemical amplification resist using an electron beam patterning machine (JBX3030: manufactured by Nippon Electron Ltd.).

[0078] Then, a baking process is performed at 110 degrees Celsius for 10 minutes, followed by spray development (SFG3000: manufactured by SIGMAMELTEC Co., Ltd.). This forms a resist pattern.

[0079] Next, the resist pattern is used as an etching mask, and the patterning of each absorption film is performed by dry etching with chlorine gas as the main component, thereby forming the absorption film pattern.

[0080] Next, the residual resist pattern is stripped off. This exposes the absorbent film pattern on the surface and sides of the absorbent film.

[0081] In this embodiment, the absorption layer pattern is an L / S (line and spacing) pattern with a linewidth of 200 nm.

[0082] Thus, the reflective photomask of Example 1 was fabricated.

[0083] It should be noted that, for the absorption film of Example 1, the reflectance Rm of the multilayer reflective film region and the reflectance Ra of the absorption film region were measured using an EUV-based reflectance measuring device. The OD value, which serves as the mask characteristic, was calculated based on these measurement results, and the results are shown in Table 1. It can be seen that the EUV reflectance in the region formed as the absorption film is 0.70%, and the OD value is 1.96.

[0084] <Example 2> Except that the thickness of the second absorption film (monolayer) was set to 11.1 nm and the thickness of the first absorption film (monolayer) formed using silicon oxide (SiO) was set to 2.5 nm, the reflective photomask blank and reflective photomask of Example 2 were fabricated in the same manner as in Example 1.

[0085] It should be noted that the refractive index n of the first absorption film is 0.97 and the extinction coefficient k is 0.013.

[0086] In addition, the total thickness of the absorption membrane is 40.8 nm.

[0087] In addition, the EUV reflectance in the absorption film region is 0.74%, and the OD value is 1.94.

[0088] <Example 3> Except that the thickness of the second absorption film (monolayer) was set to 10.9 nm and the thickness of the first absorption film (monolayer) formed using titanium oxide (TiO) was set to 2.5 nm, the reflective photomask blank and reflective photomask of Example 3 were fabricated in the same manner as in Example 1.

[0089] It should be noted that the refractive index n of the first absorption film is 0.94 and the extinction coefficient k is 0.022.

[0090] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0091] In addition, the EUV reflectance in the absorption film region is 0.63%, and the OD value is 2.01.

[0092] <Example 4> Except that the thickness of the second absorption film (monolayer) was set to 11.0 nm and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) was set to 2.4 nm, the reflective photomask blank and reflective photomask of Example 4 were fabricated in the same manner as in Example 1.

[0093] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.010.

[0094] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0095] In addition, the EUV reflectance in the absorption film region is 0.61%, and the OD value is 2.02.

[0096] <Example 5> Except that the thickness of the second absorption film (monolayer) was set to 10.8 nm and the thickness of the first absorption film (monolayer) formed using chromium oxide (CrO) was set to 2.6 nm, the reflective photomask blank and reflective photomask of Example 5 were fabricated in the same manner as in Example 1.

[0097] It should be noted that the refractive index n of the first absorption film is 0.93 and the extinction coefficient k is 0.033.

[0098] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0099] In addition, the EUV reflectance in the absorption film region is 0.67%, and the OD value is 1.99.

[0100] <Example 6> Except that the thickness of the second absorption film (monolayer) was set to 11.1 nm and the thickness of the first absorption film (monolayer) formed using hafnium oxide (HfO) was set to 2.2 nm, the reflective photomask blank and reflective photomask of Example 6 were fabricated in the same manner as in Example 1.

[0101] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.034.

[0102] In addition, the total thickness of the absorption membrane is 39.9 nm.

[0103] In addition, the EUV reflectance in the absorption film region is 0.72%, and the OD value is 1.95.

[0104] <Example 7> Except that the thickness of the second absorption film (monolayer) was set to 10.4 nm and the thickness of the first absorption film (monolayer) formed using ruthenium (Ru) was set to 2.6 nm, the reflective photomask blank and reflective photomask of Example 7 were fabricated in the same manner as in Example 1.

[0105] It should be noted that the refractive index n of the first absorption film is 0.89 and the extinction coefficient k is 0.017.

[0106] In addition, the total thickness of the absorption membrane is 39.0 nm.

[0107] In addition, the EUV reflectance in the absorption film region is 0.71%, and the OD value is 1.96.

[0108] <Example 8> Except that the thickness of the second absorption film (monolayer) was set to 11.0 nm and the thickness of the first absorption film (monolayer) formed using molybdenum (Mo) was set to 2.4 nm, the reflective photomask blank and reflective photomask of Example 8 were fabricated in the same manner as in Example 1.

[0109] It should be noted that the refractive index n of the first absorption film is 0.92 and the extinction coefficient k is 0.006.

[0110] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0111] In addition, the EUV reflectance in the absorption film region is 0.37%, and the OD value is 2.25.

[0112] <Example 9> Except that the thickness of the second absorption film (monolayer) was set to 11.3 nm and the thickness of the first absorption film (monolayer) formed using zirconium (Zr) was set to 2.1 nm, the reflective photomask blank and reflective photomask of Example 9 were fabricated in the same manner as in Example 1.

[0113] It should be noted that the refractive index n of the first absorption film is 0.96 and the extinction coefficient k is 0.004.

[0114] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0115] In addition, the EUV reflectance in the absorption film region is 0.54%, and the OD value is 2.08.

[0116] <Example 10> Except that the thickness of the second absorption film (monolayer) formed using indium (In) and tantalum (Ta) was set to 11.5 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.2 nm, the reflective photomask blank and reflective photomask of Example 10 were fabricated in the same manner as in Example 1.

[0117] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0118] In addition, the refractive index n of the second absorption film is 0.94 and the extinction coefficient k is 0.058.

[0119] In addition, the total thickness of the absorption membrane is 41.1 nm.

[0120] In addition, the EUV reflectance in the absorption film region is 0.13%, and the OD value is 2.71.

[0121] <Example 11> Except that the thickness of the second absorption film (monolayer) formed using nickel (Ni) and tantalum (Ta) was set to 11.2 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.4 nm, the reflective photomask blank and reflective photomask of Example 11 were fabricated in the same manner as in Example 1.

[0122] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0123] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.053.

[0124] In addition, the total thickness of the absorption membrane is 40.8 nm.

[0125] In addition, the EUV reflectance in the absorption film region is 0.44%, and the OD value is 2.17.

[0126] <Example 12> Except that the thickness of the second absorption film (monolayer) formed using tellurium (Te) and tantalum (Ta) was set to 10.9 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.3 nm, the reflective photomask blank and reflective photomask of Example 12 were fabricated in the same manner as in Example 1.

[0127] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0128] In addition, the refractive index n of the second absorption film is 0.96 and the extinction coefficient k is 0.057.

[0129] In addition, the total thickness of the absorption membrane is 39.6 nm.

[0130] In addition, the EUV reflectance in the absorption film region is 0.20%, and the OD value is 2.51.

[0131] <Example 13> Except that the thickness of the second absorption film (monolayer) formed using silver (Ag) and tantalum (Ta) was set to 11.4 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.6 nm, the reflective photomask blank and reflective photomask of Example 13 were fabricated in the same manner as in Example 1.

[0132] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0133] In addition, the refractive index n of the second absorption film is 0.92 and the extinction coefficient k is 0.060.

[0134] In addition, the total thickness of the absorption membrane is 42.0 nm.

[0135] In addition, the EUV reflectance in the absorption film region is 0.06%, and the OD value is 3.05.

[0136] <Example 14> Except that the thickness of the second absorption film (monolayer) formed using cobalt (Co) and tantalum (Ta) was set to 11.1 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.4 nm, the reflective photomask blank and reflective photomask of Example 14 were fabricated in the same manner as in Example 1.

[0137] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0138] In addition, the refractive index n of the second absorption film is 0.94 and the extinction coefficient k is 0.051.

[0139] In addition, the total thickness of the absorption membrane is 40.5 nm.

[0140] In addition, the EUV reflectance in the absorption film region is 0.55%, and the OD value is 2.07.

[0141] <Example 15> Except that the thickness of the second absorption film (monolayer) formed using antimony (Sb) and tantalum (Ta) was set to 11.1 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.5 nm, the reflective photomask blank and reflective photomask of Example 15 were fabricated in the same manner as in Example 1.

[0142] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0143] In addition, the refractive index n of the second absorption film is 0.94 and the extinction coefficient k is 0.053.

[0144] In addition, the total thickness of the absorption membrane is 40.8 nm.

[0145] In addition, the EUV reflectance in the absorption film region is 0.41%, and the OD value is 2.20.

[0146] <Example 16> Except that the thickness of the second absorption film (monolayer) formed using bismuth (Bi) and tantalum (Ta) was set to 11.1 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.5 nm, the reflective photomask blank and reflective photomask of Example 16 were fabricated in the same manner as in Example 1.

[0147] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0148] In addition, the refractive index n of the second absorption film is 0.94 and the extinction coefficient k is 0.049.

[0149] In addition, the total thickness of the absorption membrane is 40.8 nm.

[0150] In addition, the EUV reflectance in the absorption film region is 0.70%, and the OD value is 1.97.

[0151] <Example 17> Except that the thickness of the second absorption film (monolayer) formed using iridium (Ir) and tantalum (Ta) was set to 11.8 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.0 nm, the reflective photomask blank and reflective photomask of Example 17 were fabricated in the same manner as in Example 1.

[0152] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0153] In addition, the refractive index n of the second absorption film is 0.93 and the extinction coefficient k is 0.043.

[0154] In addition, the total thickness of the absorption membrane is 41.4 nm.

[0155] In addition, the EUV reflectance in the absorption film region is 1.13%, and the OD value is 1.76.

[0156] <Example 18> Except that the thickness of the second absorption film (monolayer) formed using rhenium (Re) and tantalum (Ta) was set to 11.7 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.0 nm, the reflective photomask blank and reflective photomask of Example 18 were fabricated in the same manner as in Example 1.

[0157] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0158] In addition, the refractive index n of the second absorption film is 0.93 and the extinction coefficient k is 0.040.

[0159] In addition, the total thickness of the absorption membrane is 41.1 nm.

[0160] In addition, the EUV reflectance in the absorption film region is 1.57%, and the OD value is 1.61.

[0161] <Example 19> Except that the thickness of the second absorption film (monolayer) formed using platinum (Pt) and tantalum (Ta) was set to 11.9 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.1 nm, the reflective photomask blank and reflective photomask of Example 19 were fabricated in the same manner as in Example 1.

[0162] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0163] In addition, the refractive index n of the second absorption film is 0.92 and the extinction coefficient k is 0.050.

[0164] In addition, the total thickness of the absorption membrane is 42.0 nm.

[0165] In addition, the EUV reflectance in the absorption film region is 0.38%, and the OD value is 2.24.

[0166] <Example 20> Except that the thickness of the second absorption film (monolayer) formed using osmium (Os) and tantalum (Ta) was set to 11.8 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.0 nm, the reflective photomask blank and reflective photomask of Example 20 were fabricated in the same manner as in Example 1.

[0167] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0168] In addition, the refractive index n of the second absorption film is 0.93 and the extinction coefficient k is 0.042.

[0169] In addition, the total thickness of the absorption membrane is 41.4 nm.

[0170] In addition, the EUV reflectance in the absorption film region is 1.19%, and the OD value is 1.73.

[0171] <Example 21> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 3.4 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 3.5 nm, the reflective photomask blank and reflective photomask of Example 21 were fabricated in the same manner as in Example 1.

[0172] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0173] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0174] In addition, the total number of layers of the first and second absorption films is 14, and the total thickness of the absorption films is 48.3 nm.

[0175] In addition, the EUV reflectance in the absorption film region is 0.23%, and the OD value is 2.45.

[0176] <Example 22> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 15.8 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 4.3 nm, the reflective photomask blank and reflective photomask of Example 22 were fabricated in the same manner as in Example 1.

[0177] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0178] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0179] In addition, the total number of layers of the first and second absorption films is 4, and the total thickness of the absorption films is 40.2 nm.

[0180] In addition, the EUV reflectance in the absorption film region is 0.51%, and the OD value is 2.11.

[0181] <Example 23> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 9.2 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.5 nm, the reflective photomask blank and reflective photomask of Example 23 were fabricated in the same manner as in Example 1.

[0182] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0183] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0184] In addition, the total number of layers of the first and second absorption films is 8, and the total thickness of the absorption films is 46.8 nm.

[0185] In addition, the EUV reflectance in the absorption film region is 0.26%, and the OD value is 2.39.

[0186] <Example 24> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 4.4 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 1.4 nm, the reflective photomask blank and reflective photomask of Example 24 were fabricated in the same manner as in Example 1.

[0187] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0188] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0189] In addition, the total number of layers of the first and second absorption films is 16, and the total thickness of the absorption films is 40.2 nm.

[0190] In addition, the EUV reflectance in the absorption film region is 0.25%, and the OD value is 2.41.

[0191] <Example 25> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 13.9 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 1.7 nm, the reflective photomask blank and reflective photomask of Example 25 were fabricated in the same manner as in Example 1.

[0192] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0193] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0194] In addition, the total thickness of the absorption membrane is 46.8 nm.

[0195] In addition, the EUV reflectance in the absorption film region is 0.22%, and the OD value is 2.47.

[0196] <Example 26> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 4.4 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.2 nm, the reflective photomask blank and reflective photomask of Example 26 were fabricated in the same manner as in Example 1.

[0197] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0198] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0199] In addition, the total number of layers of the first and second absorption films is 12, and the total thickness of the absorption films is 33.0 nm.

[0200] In addition, the EUV reflectance in the absorption film region is 1.62%, and the OD value is 1.60.

[0201] <Example 27> Except that the thickness of the second absorption film (monolayer) formed using lead (Pb) and tungsten (W) was set to 11.8 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 2.0 nm, the reflective photomask blank and reflective photomask of Example 27 were fabricated in the same manner as in Example 1.

[0202] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0203] In addition, the refractive index n of the second absorption film is 0.93 and the extinction coefficient k is 0.042.

[0204] In addition, the total thickness of the absorption membrane is 41.4 nm.

[0205] In addition, the EUV reflectance in the absorption film region is 1.19%, and the OD value is 1.73.

[0206] <Example 28> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 36.9 nm, and the thickness of the first absorption film (monolayer) formed using ruthenium (Ru) and silicon (Si) was set to 10.3 nm, the reflective photomask blank and reflective photomask of Example 28 were fabricated in the same manner as in Example 1.

[0207] It should be noted that the refractive index n of the first absorption film is 0.90 and the extinction coefficient k is 0.015.

[0208] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0209] In addition, the total number of layers of the first and second absorption films is 2, and the total thickness of the absorption films is 47.2 nm.

[0210] In addition, the EUV reflectance in the absorption film region is 0.24%, and the OD value is 2.43.

[0211] <Example 29> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 4.0 nm and the thickness of the first absorption film (monolayer) formed using ruthenium (Ru) was set to 3.9 nm, the reflective photomask blank and reflective photomask of Example 29 were fabricated in the same manner as in Example 1.

[0212] It should be noted that the refractive index n of the first absorption film is 0.89 and the extinction coefficient k is 0.017.

[0213] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0214] In addition, the total number of layers of the first and second absorption films is 10, and the total thickness of the absorption films is 39.5 nm.

[0215] In addition, the EUV reflectance in the absorption film region is 0.36%, and the OD value is 2.25.

[0216] It should be noted that in this embodiment, a first absorbent film is formed on the capping layer, and a second absorbent film is formed on the first absorbent film. That is, in this embodiment, the absorbent film is formed with the second absorbent film as the outermost layer.

[0217] <Example 30> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 16.9 nm, and the thickness of the first absorption film (monolayer) formed using aluminum (Al) and silicon (Si) was set to 5.5 nm, the reflective photomask blank and reflective photomask of Example 30 were fabricated in the same manner as in Example 1.

[0218] It should be noted that the refractive index n of the first absorption film is 1.00 and the extinction coefficient k is 0.015.

[0219] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0220] In addition, the total number of layers of the first and second absorption films is 4, and the total thickness of the absorption films is 44.8 nm.

[0221] In addition, the EUV reflectance in the absorption film region is 0.75%, and the OD value is 1.94.

[0222] <Example 31> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and tantalum (Ta) was set to 10.8 nm and the thickness of the first absorption film (monolayer) formed using tungsten (W) was set to 2.6 nm, the reflective photomask blank and reflective photomask of Example 31 were fabricated in the same manner as in Example 1.

[0223] It should be noted that the refractive index n of the first absorption film is 0.93 and the extinction coefficient k is 0.033.

[0224] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.050.

[0225] In addition, the total thickness of the absorption membrane is 40.2 nm.

[0226] In addition, the EUV reflectance in the absorption film region is 0.67%, and the OD value is 1.99.

[0227] It should be noted that the tungsten (W) used in the first absorber membrane is a material resistant to hydrogen free radicals.

[0228] <Comparative Example 1> Except that a second absorption film was not provided and the thickness of the first absorption film (monolayer) formed using tin oxide (SnO) was set to 32.4 nm, the reflective photomask blank and reflective photomask of Comparative Example 1 were fabricated in the same manner as in Example 1.

[0229] It should be noted that the refractive index n of the first absorption film is 0.93 and the extinction coefficient k is 0.070.

[0230] In addition, the total thickness of the absorption membrane is 32.4 nm.

[0231] In addition, the EUV reflectance in the absorption film region is 0.20%, and the OD value is 2.51.

[0232] <Comparative Example 2> Except that the thickness of the second absorption film (monolayer) formed using tin oxide (SnO) and zirconium (Zr) was set to 18.5 nm, and the thickness of the first absorption film (monolayer) formed using niobium oxide (NbO) and silicon (Si) was set to 1.6 nm, the reflective photomask blank and reflective photomask of Comparative Example 2 were fabricated in the same manner as in Example 1.

[0233] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.015.

[0234] In addition, the refractive index n of the second absorption film is 0.95 and the extinction coefficient k is 0.030.

[0235] In addition, the total number of layers of the first and second absorption films is 4, and the total thickness of the absorption films is 40.2 nm.

[0236] In addition, the EUV reflectance is 5.19% and the OD value is 1.10.

[0237] <Reference Example> The reflective photomask blank and reflective photomask of the reference example are existing tantalum (Ta) photomask blanks and existing tantalum (Ta) masks according to the prior art.

[0238] Except that a second absorption film was not provided and the thickness of the first absorption film (monolayer) formed using tantalum nitride (TaN) and tantalum oxide (TaO) was set to 60 nm, the reflective photomask blank and reflective photomask of the reference example were fabricated in the same manner as in Example 1.

[0239] It should be noted that the refractive index n of the first absorption film is 0.95 and the extinction coefficient k is 0.030.

[0240] In addition, the total thickness of the absorption membrane is 60.0 nm.

[0241] In addition, the EUV reflectance in the absorption film region is 1.83%, and the OD value is 1.54.

[0242] <Evaluation> For the reflective photomasks obtained in Examples 1-31, Comparative Examples 1-2, and Reference Examples above, the EUV reflectivity, OD value, and hydrogen radical resistance were evaluated using the following methods.

[0243] [EUV reflectance] In this embodiment, if the measured EUV reflectance is below 1.80%, the performance is improved compared to the existing tantalum (Ta) mask, and therefore it is qualified.

[0244] [OD value] In this embodiment, if the measured OD value is 1.5 or higher, there is no problem in its use, and therefore it is qualified.

[0245] [Hydrogen radical resistance] Hydrogen was excited using a 2.45 GHz Microwave Plasma (MWP) with a flux of 100 sscm. A reflective photomask was fabricated on one of the electrodes with an inter-electrode distance of 18 mm. The thickness change of the absorption film after hydrogen radical treatment was confirmed using atomic force microscopy (AFM) and evaluated according to the following three levels: ◎, 〇, and ×. It should be noted that the measurements were performed using an L / S pattern with a linewidth of 200 nm.

[0246] In addition, in this embodiment, "◎" and "〇" are qualified.

[0247] <Evaluation Criteria> ◎: Regarding the case where no change in film thickness was observed due to hydrogen free radicals. 〇: Regarding the observation of minute film thickness changes related to hydrogen free radicals. ×: Regarding the observed film thickness changes related to hydrogen free radicals. The evaluation results are shown in Table 1.

[0248] [Table 1]

[0249] As shown in Table 1, based on the evaluation results of Examples 1-31, Comparative Examples 1-2, and Reference Examples, if the absorber film is composed of alternating layers of a first absorber film and a second absorber film, the first absorber film is a film with excellent resistance to hydrogen free radicals, the extinction coefficient k or refractive index n of the first absorber film is different from the extinction coefficient k or refractive index n of the second absorber film, and the extinction coefficient k of the second absorber film is 0.04 or higher, then it is possible to provide a reflective photomask blank and a reflective photomask with high resistance to hydrogen free radicals, low EUV reflectivity, and high OD value.

[0250] It should be noted that the reflective photomask blank and reflective photomask according to the present invention are not limited to the above embodiments and examples, and various modifications can be made without impairing the features of the invention.

Claims

1. A reflective mask blank for manufacturing a reflective mask for pattern transfer using extreme ultraviolet light as a light source, characterized in that, The reflective mask preform includes at least: a substrate; a multilayer film formed on the substrate; a cover film formed on the multilayer film and protecting the multilayer film; and an absorbent film formed on the cover film. The absorption membrane is composed of alternating layers of a first absorption membrane and a second absorption membrane. The first absorbent membrane has high resistance to hydrogen free radicals. The extinction coefficient of the first absorption film is different from that of the second absorption film, or the refractive index of the first absorption film is different from that of the second absorption film. The extinction coefficient of the second absorption film for EUV light is greater than 0.

04.

2. The reflective mask blank according to claim 1, characterized in that, The first absorber membrane contains one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium.

3. The reflective mask blank according to claim 1, characterized in that, The second absorber contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium and rhenium.

4. The reflective mask blank according to claim 1, characterized in that, The total thickness of the absorption membrane is less than 47 nm.

5. The reflective mask blank according to claim 1, characterized in that, The first absorbent membrane and the second absorbent membrane are stacked in four or more layers.

6. The reflective mask blank according to claim 1, characterized in that, The outermost layer of the absorption membrane is the first absorption membrane.

7. The reflective mask blank according to claim 1, characterized in that, The OD value (Optical Density) calculated based on the absorption film and the multilayer film is 1.5 or higher.

8. A reflective mask, characterized in that, The reflective mask comprises at least: a substrate; a multilayer film formed on the substrate; a cover film formed on the multilayer film and protecting the multilayer film; and an absorbent film formed on the cover film and having a pattern thereon. The absorption membrane is composed of alternating layers of a first absorption membrane and a second absorption membrane. The first absorbent membrane has high resistance to hydrogen free radicals. The extinction coefficient of the first absorption film is different from that of the second absorption film, or the refractive index of the first absorption film is different from that of the second absorption film. The extinction coefficient of the second absorption film for EUV light is greater than 0.

04.

9. The reflective mask according to claim 8, characterized in that, The first absorber membrane contains one or more elements selected from tantalum, silicon, titanium, niobium, chromium, hafnium, ruthenium, molybdenum, aluminum, and zirconium.

10. The reflective mask according to claim 8, characterized in that, The second absorber contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, cobalt, tantalum, antimony, bismuth, osmium, iridium and rhenium.

11. The reflective mask according to claim 8, characterized in that, The total thickness of the absorption membrane is less than 47 nm.

12. The reflective mask according to claim 8, characterized in that, The first absorbent membrane and the second absorbent membrane are stacked in four or more layers.

13. The reflective mask according to claim 8, characterized in that, The outermost layer of the absorption membrane is the first absorption membrane.

14. The reflective mask according to claim 8, characterized in that, The OD value (Optical Density) calculated based on the absorption film and the multilayer film is 1.5 or higher.

15. The reflective mask according to claim 8, characterized in that, An oxide coating with high hydrogen radical resistance is formed on the side of the patterned second absorbent membrane.

Images