Reflective photomask blank and reflective photomask

Abstract

The present invention aims to provide a reflective photomask blank and a reflective photomask with high resistance to hydrogen radicals and minimized projection effect to improve transfer performance. The reflective photomask blank (10) according to the present embodiment includes a substrate (1), a reflective portion (7), and a low reflective portion (8). The low reflective portion (8) is composed of an absorption layer (4) and a topmost layer (5). The absorption layer (4) contains one or more selected from a first material group in a total of 50 atomic percent or more. The topmost layer (5) contains at least one or more selected from a second material group in a total of 80 atomic percent or more. The first material group is indium, tin, tellurium, cobalt, nickel, platinum, silver, copper, zinc, and bismuth, and oxides, nitrides, and oxynitrides thereof. The second material group is tantalum, aluminum, ruthenium, molybdenum, zirconium, titanium, zinc, and vanadium, and oxides, nitrides, oxynitrides, and indium oxide thereof.

Description

Technical Field

[0001] The present invention relates to a reflective photomask and a reflective photomask blank for fabricating the reflective photomask. Background Technology

[0002] In semiconductor device manufacturing processes, as semiconductor devices become increasingly miniaturized, the requirements for miniaturization in photolithography technology also increase accordingly. In photolithography, the minimum resolution size of the transferred pattern largely depends on the wavelength of the exposure light source; the shorter the wavelength, the smaller the minimum resolution size. Therefore, in semiconductor device manufacturing processes, the traditional exposure light source using a 193nm ArF excimer laser has been replaced by an exposure light source using a 13.5nm EUV (Extreme Ultraviolet) light source.

[0003] Because EUV light has a short wavelength, it can be absorbed by almost all materials at a high proportion. Therefore, unlike traditional transmissive masks, the photomask used for EUV exposure (EUV mask) is a reflective mask (see, for example, Patent Documents 1, 2, and 3). Patent Document 1 discloses that in a reflective exposure mask used for EUV lithography, two or more material layers are periodically stacked on a substrate to form a multilayer film, and a pattern composed of a nitrogen-containing metal film or a mask pattern composed of a stacked structure of metal nitride films and metal films is formed on the multilayer film. In addition, Patent Document 2 discloses a reflective EUV mask comprising: a phase control film serving as an absorber film on the multilayer reflective film, and a stacked structure formed on the phase control film by alternating layers of high-refractive-index material layers and low-refractive-index material layers. In addition, Patent Document 3 discloses an EUV photomask obtained by forming a reflective layer on a glass substrate, which consists of a multilayer film composed of alternating layers of molybdenum (Mo) and silicon (Si), forming a light-absorbing layer with tantalum (Ta) as the main component, and forming a pattern on the light-absorbing layer.

[0004] As mentioned above, EUV lithography cannot use refractive optical systems that utilize light transmission; therefore, the optical system components of the exposure unit use mirrors instead of lenses. Consequently, there is a problem that the incident and reflected light directed towards the EUV photomask (reflective photomask) cannot be designed to be coaxial. In EUV lithography, the following method is typically used: the optical axis is tilted 6 degrees relative to the vertical direction of the EUV photomask to incident EUV light, and the reflected light, reflected at a negative 6-degree angle, illuminates the semiconductor substrate.

[0005] Thus, in EUV lithography, due to the tilting of the optical axis, the EUV light incident on the EUV photomask will form a shadow of the EUV photomask pattern (absorption layer pattern), thereby degrading the transfer performance, i.e., producing the so-called "projection effect (shadowing effect)" problem.

[0006] To address this issue, Patent Document 1 discloses a method that, by using a material with an extinction coefficient k of 0.03 or higher for EUV as the constituent material of the phase control film and the low refractive index material layer, a thinner absorber layer (film thickness less than 60 nm) can be formed compared to conventional films, thereby reducing the projection effect. Furthermore, Patent Document 2 discloses a method that, for conventional absorber layers or phase-shifting films with Ta as the main component, by using a compound material with high absorption (extinction coefficient k) for EUV light, the film thickness can be reduced, thereby decreasing the projection effect.

[0007] Furthermore, in existing EUV exposure equipment, hydrogen radicals are mostly used for cleaning to prevent contamination of the chamber due to the introduction of impurities (so-called contaminants). Since photomasks are mostly exposed to a hydrogen radical environment, their durability against hydrogen radicals may decrease, and their lifespan may be shortened. Therefore, photomasks need to be formed from compound materials with high resistance to hydrogen radicals.

[0008] However, neither Patent Document 1 nor Patent Document 2 mentions hydrogen radical resistance, nor is it clear whether they are photomasks capable of withstanding long-term use. Furthermore, Patent Document 2 describes a method for forming a low-reflectance film (low-reflection portion) for EUV light on the absorption layer, but it makes no mention of the increased projection effect due to the increased combined thickness of the absorber layer and the low-reflectance film caused by forming the low-reflection portion, nor is it clear whether it is an EUV photomask with high transferability.

[0009] Furthermore, in existing EUV mask preforms, a tantalum (Ta) film with a thickness of 60 nm to 90 nm is used as the light-absorbing layer. When pattern transfer is performed using an EUV mask fabricated using this preform, depending on the relationship between the incident direction of the EUV light and the orientation of the mask pattern, a decrease in contrast may occur at the edges where the mask pattern becomes a shadow. Consequently, problems such as increased edge roughness of the transferred pattern on the semiconductor substrate or the inability to form linewidths to the target dimensions may arise, potentially degrading the transfer performance.

[0010] Therefore, reflective photomask preforms were studied by changing the light-absorbing layer from tantalum (Ta) to a material with high absorption (extinction coefficient) for EUV light, or by adding a material with high absorption to tantalum (Ta). For example, Patent Document 4 describes a reflective photomask preform in which the light-absorbing layer is composed of a material containing at least 50 atomic percent (at%) Ta as the main component and further containing at least one element selected from Te, Sb, Pt, I, Bi, Ir, Os, W, Re, Sn, In, Po, Fe, Au, Hg, Ga, and Al.

[0011] Furthermore, it is known that mirrors are contaminated by byproducts of EUV (such as Sn) or carbon. As these contaminants accumulate on the mirror, the reflectivity of the mirror surface decreases, reducing the throughput of the lithography apparatus. To address this problem, Patent Document 5 discloses a method for removing contaminants from the mirror by generating hydrogen radicals within the apparatus and reacting these hydrogen radicals with the contaminants.

[0012] However, in the reflective photomask preform described in Patent Document 4, the resistance of the light-absorbing layer to hydrogen radicals (hydrogen radical resistance) was not investigated. Therefore, the transfer pattern (mask pattern) formed on the light-absorbing layer by introducing it into the EUV exposure apparatus cannot be stably maintained, and as a result, the transferability may deteriorate.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent No. 6408790

[0016] Patent Document 2: International Publication No. 2011 / 004850

[0017] Patent Document 3: Japanese Patent Application Publication No. 2011-176162

[0018] Patent Document 4: Japanese Patent Application Publication No. 2007-273678

[0019] Patent Document 5: Japanese Patent Application Publication No. 2011-530823 Summary of the Invention

[0020] The problem to be solved by the present invention

[0021] The purpose of this invention is to provide EUV photomask preforms (reflective photomask preforms) and EUV photomasks (reflective photomasks) that have high resistance to hydrogen radicals and minimize projection effects to improve transferability.

[0022] Methods for solving problems

[0023] To achieve the above objectives, one aspect of the present invention relates to a reflective photomask preform for fabricating a reflective photomask for pattern transfer using extreme ultraviolet light as a light source. The preform comprises: a substrate, a reflective portion formed on the substrate and reflecting incident light, and a low-reflectivity portion formed on the reflective portion and absorbing incident light. The low-reflectivity portion is characterized by being a stacked structure of at least two layers, consisting of an absorption layer and an outermost layer; at least one of the absorption layers contains at least 50 atomic percent of one or more materials selected from a first group of materials; and the outermost layer contains at least 80 atomic percent of one or more materials selected from the first group of materials. More than % are selected from at least one of the second material groups, wherein the first material group is indium (In), tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn) and bismuth (Bi), and their oxides, nitrides and oxynitrides, and the second material group is tantalum (Ta), aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn) and vanadium (V), and their oxides, nitrides, oxynitrides, and indium oxide (InxOy (y>1.5x)).

[0024] Furthermore, another aspect of the present invention relates to a reflective photomask preform for fabricating a reflective photomask for pattern transfer using extreme ultraviolet light as a light source. This preform comprises: a substrate, a reflective portion formed on the substrate and reflecting incident light, and a low-reflectivity portion formed on the reflective portion and absorbing incident light. The low-reflectivity portion is characterized by being a stacked structure of at least two layers, consisting of an absorption layer and an outermost layer. At least one layer of the absorption layer comprises indium oxide, and the outermost layer comprises tantalum (Ta), aluminum (Al), silicon (Si), palladium (Pd), zirconium (Zr), hafnium (Hf), niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), and bismuth (Bi), and any one or more of their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0025] In addition, the absorber layer may be formed of a material containing a total of 50 atomic percent or more of indium (In) and oxygen (O), and the atomic ratio of oxygen (O) to indium (In) (O / In) may be more than 1 and less than 1.5.

[0026] In addition, the absorber layer may further comprise any one or more of beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), ruthenium (Ru), silver (Ag), barium (Ba), iridium (Ir), gold (Au), silicon (Si), germanium (Ge), hafnium (Hf), tantalum (Ta), aluminum (Al), palladium (Pd), zirconium (Zr), niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), tellurium (Te), tungsten (W), molybdenum (Mo), and tin (Sn), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0027] In addition, the outermost layer may contain any one or more of transition elements, bismuth (Bi), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0028] In addition, the absorption layer can be divided into multiple layers, and even when divided into multiple layers, the total film thickness is in the range of 17 nm to 47 nm and the OD value (Optica Density) is 1.0 or higher.

[0029] Furthermore, even when the absorber layer is divided into multiple layers, the total film thickness can be in the range of 17 nm to 45 nm.

[0030] Furthermore, the film thickness of the low-reflection portion can be less than 60 nm, and the film thickness of the outermost layer can be greater than 1.0 nm.

[0031] To achieve the above objectives, one aspect of the present invention relates to a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate, a reflective portion formed on the substrate and reflecting incident light, and a low-reflectivity portion formed on the reflective portion and absorbing incident light. The low-reflectivity portion is characterized by being a stacked structure of at least two layers, consisting of an absorption layer and an outermost layer; at least one of the absorption layers comprises at least 50 atomic percent of one material selected from a first group of materials; and the outermost layer comprises at least 80 atomic percent of one material selected from a first group of materials. The first material group includes at least one of the following: indium (In), tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn), and bismuth (Bi), as well as their oxides, nitrides, and oxynitrides; and the second material group includes tantalum (Ta), aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn), and vanadium (V), as well as their oxides, nitrides, oxynitrides, and indium oxide (InxOy (y > 1.5x)).

[0032] In addition, other aspects of the present invention relate to a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, comprising: a substrate, a reflective portion formed on the substrate and reflecting incident light, and a low-reflectivity portion formed on the reflective portion and absorbing incident light, characterized in that the low-reflectivity portion is a stacked structure of at least two layers consisting of an absorption layer and an outermost layer, at least one of the absorption layer comprising indium oxide, and the outermost layer comprising tantalum (Ta), aluminum (Al), silicon (Si), palladium (Pd), zirconium (Zr), hafnium (Hf), niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), and bismuth (Bi), and any one or more of their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0033] In addition, the absorber layer may be formed of a material containing a total of 50 atomic percent or more of indium (In) and oxygen (O), and the atomic ratio of oxygen (O) to indium (In) (O / In) may be more than 1 and less than 1.5.

[0034] In addition, the absorber layer may further comprise any one or more of beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), ruthenium (Ru), silver (Ag), barium (Ba), iridium (Ir), gold (Au), silicon (Si), germanium (Ge), hafnium (Hf), tantalum (Ta), aluminum (Al), palladium (Pd), zirconium (Zr), niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), tellurium (Te), tungsten (W), molybdenum (Mo), and tin (Sn), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0035] In addition, the outermost layer may contain any one or more of transition elements, bismuth (Bi), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0036] In addition, the film thickness of the low-reflection portion can be less than 60 nm. Even if the absorption layer is divided into multiple layers, the total film thickness of each layer can be more than 17 nm and less than 47 nm, and the film thickness of the outermost layer can be more than 1 nm.

[0037] Furthermore, even when the absorber layer is divided into multiple layers, the total film thickness of each layer can be between 17 nm and 45 nm.

[0038] The effects of the invention

[0039] According to one aspect of the present invention, by forming a low-reflectivity portion composed of a compound material with high EUV absorption and a compound material with high hydrogen radical resistance on the outermost layer, the dimensional and shape accuracy of the pattern transferred onto the wafer can be improved, and the photomask can be used for a long time. That is, according to one aspect of the present invention, an EUV photomask preform (reflective photomask preform) and an EUV photomask (reflective photomask) with high resistance to hydrogen radicals and minimizing projection effects to improve transferability can be provided. Attached Figure Description

[0040] [ Figure 1 [Illustration 1] is a schematic cross-sectional view showing the structure of a reflective photomask blank according to various embodiments of the present invention.

[0041] [ Figure 2 [Illustration 1] is a schematic cross-sectional view showing the structure of a reflective photomask according to various embodiments of the present invention.

[0042] [ Figure 3 [ ] is a graph showing the optical constants of the metals contained in the first and second material groups at the wavelength of EUV light.

[0043] [ Figure 4 [Illustration] is a schematic diagram illustrating the hydrogen radical tolerance evaluation method according to various embodiments of the present invention.

[0044] [ Figure 5 [ ] is a graph showing the refractive index n and extinction coefficient k at the wavelength of EUV light.

[0045] [ Figure 6 [Illustration 1] is a schematic cross-sectional view showing the structure of a reflective photomask blank according to an embodiment of the present invention.

[0046] [ Figure 7 [Illustrated cross-sectional view] is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present invention.

[0047] [ Figure 8 [Illustrated cross-sectional view] is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present invention.

[0048] [ Figure 9 [Illustrated cross-sectional view] is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present invention.

[0049] [ Figure 10 [Illustrated cross-sectional view] is a schematic cross-sectional view showing the manufacturing process of a reflective photomask according to an embodiment of the present invention.

[0050] [ Figure 11 [Illustration 1] is a schematic cross-sectional view showing the structure of a reflective photomask according to an embodiment of the present invention.

[0051] [ Figure 12 [Illustration] is a schematic plan view showing the design pattern of a reflective photomask according to an embodiment of the present invention. Detailed Implementation

[0052] Hereinafter, the reflective photomask blank and the various configurations of the reflective photomask according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown below. In the embodiments shown below, technically preferred limitations have been made for carrying out the present invention, but these limitations are not necessary conditions for the present invention.

[0053] Figure 1 This is a schematic cross-sectional view showing the structure of the reflective photomask blank 10 according to various embodiments of the present invention. Additionally, Figure 2 This is a schematic cross-sectional view illustrating the structure of the reflective photomask 20 according to various embodiments of the present invention. Here, Figure 2 The reflective photomask 20 shown in the various embodiments of the present invention is constructed by making... Figure 1The low-reflectivity portion 8 of the reflective photomask blank 10 shown in the various embodiments of the present invention is formed by patterning.

[0054] [First Embodiment]

[0055] (Overall structure)

[0056] like Figure 1 As shown, the reflective photomask blank 10 according to an embodiment of the present invention includes: a substrate 1, a multilayer reflective film 2 formed on the substrate 1, and a capping layer 3 formed on the multilayer reflective film 2. Thus, a reflective portion 7 having the multilayer reflective film 2 and the capping layer 3 is formed on the substrate 1. The reflective photomask blank 10 according to an embodiment of the present invention includes a low-reflection portion 8 on the reflective portion 7. The low-reflection portion 8 is composed of at least two layers, one of which is an absorption layer 4, and an outermost layer 5 is provided on the absorption layer 4.

[0057] (Substrate)

[0058] The substrate 1 according to embodiments of the present invention can be, for example, a flat Si substrate or a synthetic quartz substrate. Alternatively, the substrate 1 can be a low-thermal-expansion glass with added titanium, but any material with a low coefficient of thermal expansion is acceptable; the present invention is not limited to these.

[0059] (Reflective part)

[0060] Multilayer reflective film

[0061] The multilayer reflective film 2 according to various embodiments of the present invention only needs to reflect EUV light (extreme ultraviolet light) as exposure light, and preferably is a multilayer reflective film formed by combining materials with very different refractive indices for EUV light. Preferably, the multilayer reflective film 2 can be formed, for example, by repeatedly stacking a combination layer of Mo (molybdenum) and Si (silicon), or Mo (molybdenum) and Be (beryllium) for about 40 cycles.

[0062] (Capping layer)

[0063] The capping layer 3 according to various embodiments of the present invention is formed of a material resistant to dry etching when forming a transfer pattern (mask pattern) on the absorption layer 4, and functions as an etching barrier layer to prevent damage to the multilayer reflective film 2 during etching of the low-reflection pattern described later. The capping layer 3 is, for example, formed of Ru (ruthenium). Here, depending on the material of the multilayer reflective film 2 and the etching conditions, the capping layer 3 may not be provided. Furthermore, although not shown, a back conductive film may be formed on the surface of the substrate 1 where the multilayer reflective film 2 is not formed. The back conductive film is a film used to fix the reflective photomask 20 described later on the exposure machine using the principle of an electrostatic chuck.

[0064] (Low-reflection area)

[0065] like Figure 2 As shown, the low-reflection portion 8 in each embodiment of the present invention is a layer formed by removing a portion of the low-reflection portion 8 of the reflective photomask blank 10 to form a low-reflection portion pattern 8a.

[0066] In EUV lithography, EUV light is incident at an angle and reflected by the reflective portion 7. However, due to the projection effect caused by the low-reflectivity pattern 8a obstructing the light path, the transfer performance onto the wafer (semiconductor substrate) may deteriorate. This deterioration in transfer performance can be reduced by decreasing the thickness of the low-reflectivity portion 8 that absorbs EUV light. To reduce the thickness of the low-reflectivity portion 8, it is preferable to use a material with high absorption of EUV light compared to conventional materials, i.e., a material with a high extinction coefficient k for a wavelength of 13.5 nm, as the absorption layer 4.

[0067] <Absorbing Layer>

[0068] The extinction coefficient k of tantalum (Ta), the main material of the conventional absorption layer 4, is 0.041. If a compound material with an extinction coefficient k greater than that of tantalum (Ta) is used, the thickness of the absorption layer 4 (low-reflection part 8) can be reduced compared to the conventional method. Figure 3 A graph showing the optical constants of tantalum (Ta) and the first material group described later. According to Figure 3 It can be seen that the materials included in the first material group all have a larger extinction coefficient k than traditional materials, which can reduce the projection effect.

[0069] However, indium (In) is only included in the second group of materials described later when it is indium oxide (InxOy (y>1.5x)).

[0070] Here, in this embodiment, "the first material group" refers to the group of materials composed of indium (In), tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn), and bismuth (Bi), and their oxides, nitrides, and oxynitrides. That is, at least one layer constituting the absorption layer 4 in this embodiment contains at least one material selected from the group of indium (In), tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn), and bismuth (Bi), and their oxides, nitrides, and oxynitrides, totaling 50 atomic percent or more. The materials constituting the first material group have a large extinction coefficient k; therefore, when at least one layer constituting the absorption layer 4 is formed of a material constituting the first material group, the transfer performance can be improved.

[0071] Among the materials in Group 1, tin (Sn) is particularly preferred because it is oxidized, which increases its thermal stability, and it is easy to process with reactive gases.

[0072] In this embodiment, the absorber layer 4 can be a compound material selected from at least one material from the first material group described above, or a mixture of materials with other materials. However, to reduce the projection effect, the total film thickness of the absorber layer 4 is preferably 47 nm or less. If the total film thickness of the absorber layer 4 exceeds 47 nm, pattern transfer may not be improved due to the projection effect. If the total film thickness of the absorber layer 4 is less than 17 nm, the OD value may be less than 1, and pattern transfer may not be improved.

[0073] Furthermore, in order to maintain the contrast required for pattern transfer, the mixing ratio of the materials constituting the absorption layer 4 in this embodiment needs to be a mixing ratio calculated such that the OD value is 1 or higher. The lower limit of the mixing ratio of the materials constituting the absorption layer 4 in this embodiment depends on the optical constants of the other materials being mixed and cannot be determined in general. However, in order to reduce the projection effect compared to conventional films, it is desirable that the materials constituting the first material group be compound materials containing at least 50 atomic percent or more.

[0074] Furthermore, in order to transfer fine patterns, it is desirable to have a high contrast in the intensity of light reflected from the reflective portion 7 and the low-reflection portion 8, respectively. Therefore, the OD value of the absorption layer 4 is more preferably 1.5 or higher.

[0075] The absorber layer 4 is formed on the capping layer 3, for example, by sputtering. However, in order to improve the roughness and in-plane dimensional uniformity of the etched absorber layer pattern, or the in-plane uniformity of the transferred image, the film of the absorber layer 4 is preferably sufficiently amorphous. Therefore, the absorber layer 4 can be formed from a compound material containing less than 50 atomic percent of at least one material selected from boron (B), nitrogen (N), silicon (Si), germanium (Ge) and hafnium (Hf), and their oxides, nitrides and oxynitrides.

[0076] In addition to the first material group, the absorption layer 4 can also be formed by mixing other materials to improve amorphousness, improve washability, prevent mixing, improve the contrast of inspection light, phase shift, etc.

[0077] It should be noted that the absorption layer 4 can be a single-layer structure or a multi-layer structure. When the absorption layer 4 is a multi-layer structure, each layer can be formed with different compositions. For example, the bottom layer of the absorption layer 4 can be formed of the material with the largest extinction coefficient k among the materials constituting the first material group, and stacked in such a way that the extinction coefficient k of the materials constituting the first material group decreases sequentially. Alternatively, the bottom layer of the absorption layer 4 can be formed of the material with the smallest extinction coefficient k among the materials constituting the first material group, and stacked in such a way that the extinction coefficient k of the materials constituting the first material group increases sequentially.

[0078] <Outermost layer>

[0079] As mentioned above, in EUV exposure machines, photomasks are mostly exposed to hydrogen radical environments, so it is necessary to use compound materials with high hydrogen radical resistance to extend the life of photomasks.

[0080] like Figure 4 As shown, a compound material with a film reduction rate of less than 0.1 nm / s under the following environment is selected as the material with high hydrogen radical resistance in this embodiment. This environment is characterized by a hydrogen flow rate of 10. 19 at / (cm 2 s), a hydrogen radical environment excited using 40MHz CCP (Capacitively Coupled Plasma) with an electrode spacing of 18mm.

[0081] It should be noted that the evaluation of hydrogen radical resistance in this embodiment is not limited to the evaluation method described above. For example, materials with a film reduction rate of less than 0.1 nm / s under the following conditions can also be regarded as materials with high hydrogen radical resistance: a hydrogen radical-rich environment in a vacuum of less than 0.36 mbar using a microwave plasma with a power of 1 kW to generate hydrogen plasma.

[0082] Here, regarding the measured values ​​of membrane reduction rate, the difference between the two methods is extremely small, yielding almost identical values.

[0083] The outermost layer 5 contains at least 80 atomic percent of at least one material selected from the second group of materials described later, which are materials that meet the conditions for being materials with high free radical resistance. In addition to the second group of materials, the compound material of the outermost layer 5 may be mixed with other materials, but in order not to reduce free radical resistance, it is desirable that the outermost layer 5 is composed of a compound material containing at least 80 atomic percent of the material from the second group of materials.

[0084] Here, in this embodiment, "the second material group" refers to the group of materials composed of tantalum (Ta), aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn), and vanadium (V), and their oxides, nitrides, oxynitrides, and indium oxides (InxOy (y > 1.5x)). That is, the outermost layer 5 in this embodiment contains at least one material selected from the group of materials composed of tantalum (Ta), aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn), indium (In), and vanadium (V), and their oxides, nitrides, and oxynitrides, totaling 80 atomic percent or more.

[0085] Since the film thickness of the low-reflection portion 8 is the combined thickness of the absorption layer 4 and the outermost layer 5, the projection effect may increase. Therefore, it is desirable that the combined film thickness of the absorption layer 4 and the outermost layer 5 be 60 nm or less. Furthermore, when using a compound material with sufficient hydrogen radical resistance as the outermost layer 5, the film thickness of the outermost layer 5 is preferably 1.0 nm or more to obtain a stable film thickness distribution. Additionally, to minimize the shading effect, the film thickness of the outermost layer 5 can be 10 nm or less.

[0086] The outermost layer 5 is formed on the absorber layer 4, for example, by sputtering. However, in order to improve the roughness and in-plane dimensional uniformity of the etched outermost layer pattern, or the in-plane uniformity of the transferred image, the film of the outermost layer 5 is preferably sufficiently amorphous. Therefore, the outermost layer 5 can be formed from a compound material containing at least 20% of a composition of boron (B), nitrogen (N), germanium (Ge) and hafnium (Hf), and their oxides, nitrides and oxynitrides.

[0087] It should be noted that, in addition to the materials mentioned above, the material constituting the outermost layer 5 may also be a material containing at least 20% of an element selected from beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), germanium (Ge), arsenic (As), strontium (Sr), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), silver (Ag), barium (Ba), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), gold (Au), and radium (Ra), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0088] As described above, a compound material with Ta as the main component has been used in the absorption layer 4 of a conventional EUV reflective photomask. In this case, in order to obtain an optical density OD (Equation 1) of 1 or more, which is an index representing the contrast between the light intensity of the absorption layer 7 and the low-reflection part 8, the film thickness needs to be 40 nm or more, and in order to obtain an OD value of 2 or more, the film thickness needs to be 70 nm or more.

[0089] OD = -log(Ra / Rm)···(Equation 1)

[0090] It should be noted that in Equation 1 above, the intensity of the reflected light from the reflective part 7 is represented as "Rm", and the intensity of the reflected light from the low-reflection part 8 is represented as "Ra".

[0091] It should be noted that in traditional EUV reflective photomasks, as described above, in a compound material with Ta as the main component, the film thickness is 60 nm, and the reflectivity from the low-reflectivity part 8 is about 2%, which translates to an OD of about 1.5 with respect to the reflective part 7. A higher OD value results in better contrast and higher transferability. Pattern transfer requires an OD value > 1, but compared to the conventional method described above, an OD value of 1.5 or higher is more preferable.

[0092] [Second Implementation]

[0093] Except for the configurations of the absorption layer 4 and the outermost layer 5, the configurations of the reflective photomask blank 10 and the reflective photomask 20 according to the second embodiment of the present invention are the same as those of the reflective photomask blank 10 and the reflective photomask 20 according to the first embodiment of the present invention described above. Therefore, in this embodiment, the parts that differ from those in the first embodiment of the present invention, namely the absorption layer 4 and the outermost layer 5, will be described, while other parts will be omitted from the description.

[0094] <Absorbing Layer>

[0095] Figure 5 This is a graph showing the optical constants of a portion of metallic materials relative to EUV light with a wavelength of 13.5 nm. Figure 5 The horizontal axis represents the refractive index n, and the vertical axis represents the extinction coefficient k. The extinction coefficient k of tantalum (Ta), the main material of the conventional absorption layer 4, is 0.041. If a material with a larger extinction coefficient k than Ta is used, the thickness of the absorption layer 4 can be reduced compared to the conventional method.

[0096] As a material that satisfies the extinction coefficient k as described above, such as Figure 5 As shown, for example, silver (Ag), platinum (Pt), indium (In), cobalt (Co), tin (Sn), nickel (Ni), and tellurium (Te).

[0097] As described above, a compound material with Ta as the main component has been used in the absorption layer 4 of a conventional EUV reflective photomask. In this case, as explained in the first embodiment, in order to obtain an OD value of 1 or higher, the film thickness of the absorption layer 4 needs to be 40 nm or higher, and in order to obtain an OD value of 2 or higher, the film thickness of the absorption layer 4 needs to be 70 nm or higher. The extinction coefficient k of Ta is 0.041, but by applying a material containing indium (In) and oxygen (O) with an extinction coefficient k of 0.06 or higher to the absorption layer 4, if the OD value is at least 1 or higher, the film thickness of the absorption layer 4 can be as thin as 17 nm, if the OD value is 1.8 or higher, the film thickness of the absorption layer 4 can be 47 nm or less, and if the OD value is 2 or higher, the film thickness of the absorption layer 4 can be 45 nm or less. However, when the film thickness of the absorption layer 4 exceeds 47 nm, the pattern transfer may not be improved due to the projection effect.

[0098] Therefore, it is preferable that the absorber layer 4 according to the second embodiment of the present invention is mainly composed of a material containing indium (In) and oxygen (O), and has a film thickness of 17 nm to 47 nm. That is, when the film thickness of the absorber layer 4 is in the range of 17 nm to 47 nm, compared with a conventional absorber layer 4 formed of a compound material mainly composed of Ta, the projection effect can be sufficiently reduced, thereby improving the transfer performance. In addition, when the film thickness of the absorber layer 4 is in the range of 17 nm to 45 nm, compared with a conventional absorber layer 4 formed of a compound material mainly composed of Ta, the OD value can be increased, thereby improving the transfer performance.

[0099] In addition, the aforementioned "main components" refers to components that contain more than 50 atomic percent relative to the total number of atoms in the absorption layer.

[0100] Furthermore, in order to transfer fine patterns, similar to the first embodiment, it is desirable to have a high contrast in the intensity of light reflected from the reflective portion 7 and the low-reflective portion 8. Therefore, the OD value of the absorption layer 4 is more preferably 1.5 or higher.

[0101] The material containing indium (In) and oxygen (O) used to form the absorber layer 4 is preferably between 1:1 and 1:1.5. That is, in the absorber layer 4, the atomic ratio of oxygen (O) to indium (In) (O / In) is preferably 1 or more and 1.5 or less. It should be noted that this range is based on the fact that the heat resistance decreases when the atomic ratio is less than 1 and the stoichiometry is maximized when the atomic ratio is 1.5.

[0102] It should be noted that, Figure 1 and Figure 2A single-layer absorber layer 4 is shown, but the absorber layer 4 involved in this embodiment is not limited to this. The absorber layer 4 involved in this embodiment can be, for example, one or more absorber layers, that is, a multilayer absorber layer. That is, the absorber layer 4 involved in this embodiment can be divided into multiple layers, and even in this case, the total film thickness of the combined film thickness of each absorber layer 4 is preferably 17 nm or more and 47 nm or less, and preferably 17 nm or more and 45 nm or less.

[0103] Furthermore, the material constituting the absorber layer 4 preferably contains a total of 50 atomic% or more of indium (In) and oxygen (O). This is because when the absorber layer 4 contains components other than indium (In) and oxygen (O), the EUV light absorption may decrease, but if the components other than indium (In) and oxygen (O) are less than 50 atomic%, the EUV light absorption will only decrease slightly, and the function of the absorber layer 4 as an EUV mask will hardly be reduced.

[0104] An absorber layer 4 is formed on the capping layer 3. As a material other than indium (In) and oxygen (O), it can be, for example, made of a material containing less than 50 atomic percent of a component selected from beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), ruthenium (Ru), silver (Ag), barium (Ba), iridium (Ir), gold (Au), silicon (Si), germanium (Ge), hafnium (Hf), tantalum (Ta), aluminum (Al), palladium (Pd), zirconium (…). The material comprises at least one of the following: Zr, niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), tellurium (Te), tungsten (W), molybdenum (Mo), tin (Sn), arsenic (As), strontium (Sr), technetium (Tc), rhodium (Rh), rhenium (Re), osmium (Os), and radium (Ra), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0105] By including (for example) beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), copper (Cu), germanium (Ge), arsenic (As), strontium (Sr), technetium (Tc), rhodium (Rh), barium (Ba), tungsten (W), rhenium (Re), osmium (Os), gold (Au) in the material constituting the absorption layer 4, the roughness, in-plane dimensional uniformity, and in-plane uniformity of the transferred image can be improved, thus making it a sufficiently amorphous material.

[0106] In addition, by including materials such as silver (Ag), nickel (Ni), tellurium (Te), and tin (Sn) in the material constituting the absorption layer 4, it can become a material with an extinction coefficient k greater than that of the conventional main material, namely tantalum (Ta).

[0107] Furthermore, by including materials constituting the absorber layer 4 such as tantalum (Ta), silicon (Si), zirconium (Zr), hafnium (Hf), niobium (Nb), yttrium (Y), lead (Pb), gallium (Ga), etc., the material is less likely to react with hydrogen free radicals, thus becoming a material with further hydrogen free radical resistance.

[0108] In addition, by making the material constituting the absorbent layer 4 contain, for example, aluminum (Al), chromium (Cr), zirconium (Zr), etc., it has low reactivity to chemical solutions such as SPM or APM commonly used for mask cleaning, and can become a material with further cleaning resistance.

[0109] Furthermore, by including materials constituting the absorption layer 4 such as silicon nitride (SiN) and tantalum oxide (TaO), it is possible to make a material with improved light absorption at wavelengths of 190nm to 260nm and improved contrast of inspection light.

[0110] In addition, by including (for example) cobalt (Co), ruthenium (Ru), iridium (Ir), gold (Au), palladium (Pd), platinum (Pt), molybdenum (Mo) in the material constituting the absorption layer 4, it is possible to make a material with a refractive index n of less than 0.95 for a wavelength of 13.5 nm and improve phase shift.

[0111] The above describes one example of the effect of the materials that can be contained in the absorption layer 4, but the effects of each material are not limited to the example above and may correspond to multiple effects.

[0112] Furthermore, as described in the first embodiment, the reflective photomask 20 is exposed to a hydrogen radical environment. Therefore, it cannot withstand prolonged use unless it is a light-absorbing material with high hydrogen radical resistance. In this embodiment, a material with a film reduction rate of less than 0.1 nm / s is selected as a material with high hydrogen radical resistance. This environment is a hydrogen radical-rich environment in which hydrogen plasma is generated using a microwave plasma with a power of 1 kW in a vacuum of less than 0.36 mbar.

[0113] It should be noted that the evaluation of hydrogen radical resistance in this embodiment is not limited to the evaluation method described above. For example, such as Figure 4 As shown, compound materials with a film reduction rate of less than 0.1 nm / s under the following environment can also be used as materials with high hydrogen radical resistance, where the hydrogen flow rate is set to 10. 19 at / (cm 2 s), a hydrogen radical environment excited using a 40MHz CCP (Capacitively Coupled Plasma) with an electrode spacing of 18mm.

[0114] Here, regarding the measured values ​​of membrane reduction rate, the difference between the two methods is extremely small, yielding almost identical values.

[0115] It is known that among materials that satisfy the nk value combination, indium (In) monomers have low resistance to hydrogen radicals.

[0116] It should be noted that in the evaluation test of the membrane reduction rate shown in Table 1, the membrane reduction rate was measured repeatedly. The case where the membrane reduction rate was all below 0.1 nm / s was evaluated as "○"; the case where there was a reduction of several nm at the beginning of the hydrogen radical treatment, but the subsequent membrane reduction rate was below 0.1 nm / s was evaluated as "△"; and the case where the membrane reduction rate was all above 0.1 nm / s was evaluated as "×".

[0117] In addition, the above atomic ratio (O / In ratio) is the result of measuring the film thickness of 1 μm using EDX (energy dispersive X-ray diffraction).

[0118] The evaluation results are shown in Table 1.

[0119] [Table 1]

[0120] O / In ratio 1.0 1.5 Hydrogen radical resistance × △

[0121] When the O / In ratio is 1.0, the membrane shrinkage rate is high; when the O / In ratio is 1.5, slight membrane shrinkage occurs.

[0122] <Outermost layer>

[0123] In this embodiment, similar to the first embodiment, it is effective to provide a material with high resistance to hydrogen free radicals in the outermost layer. To avoid reducing hydrogen free radical resistance, it is desirable that the outermost layer 5 be formed of a material containing at least 80 atomic percent of a material with hydrogen free radical resistance. Therefore, it is desirable that the outermost layer 5 be composed, for example, of a material containing at least 80 atomic percent of any one or more of the following: tantalum (Ta), aluminum (Al), silicon (Si), palladium (Pd), zirconium (Zr), hafnium (Hf), niobium (Nb), chromium (Cr), platinum (Pt), yttrium (Y), nickel (Ni), lead (Pb), titanium (Ti), gallium (Ga), and bismuth (Bi), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides. It should be noted that the material constituting the outermost layer 5 may also include materials other than those described above.

[0124] Similar to the first embodiment, since the film thickness of the low-reflection portion 8 is the combined thickness of the absorption layer 4 and the outermost layer 5, the projection effect may increase. Therefore, similar to the first embodiment, it is desirable that the total thickness of each layer of the absorption layer 4 and the outermost layer 5 be 60 nm or less. Furthermore, when using a material with sufficient hydrogen radical resistance to form the outermost layer 5, in order to obtain a stable film thickness distribution, similar to the first embodiment, the film thickness of the outermost layer 5 is preferably 1 nm or more.

[0125] The absorber layer 4 was made of indium oxide (O / In = 1.5), and the outermost layer 5 was made of tantalum oxide (TaO). Evaluation tests were conducted to assess the film reduction rate for each thickness of the outermost layer 5. It should be noted that the evaluation criteria used in this evaluation are the same as those used in the film reduction rate evaluation tests shown in Table 1.

[0126] The results are shown in Table 2.

[0127] [Table 2]

[0128] TaO film thickness (nm) 1 5 10 Hydrogen radical resistance ○ ○ ○

[0129] As shown in Table 2, no film reduction occurred when the tantalum oxide (TaO) film thickness was 1 nm, 5 nm, or 10 nm.

[0130] The outermost layer 5 is formed on the absorption layer 4. However, in order to improve the roughness and in-plane dimensional uniformity of the etched absorption pattern 7a and the in-plane uniformity of the transferred image, similar to the first embodiment, the film is preferably sufficiently amorphous. Therefore, the material constituting the outermost layer 5 may be, for example, a material containing at least one element selected from beryllium (Be), calcium (Ca), scandium (Sc), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), germanium (Ge), arsenic (As), strontium (Sr), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), silver (Ag), barium (Ba), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), gold (Au), and radium (Ra), and their oxides, nitrides, fluorides, borides, oxynitrides, oxyborides, and oxynitride-borides.

[0131] It should be noted that, in addition to the materials mentioned above, the material constituting the outermost layer 5 may be, for example, a compound material containing at least one element selected from boron (B), nitrogen (N), germanium (Ge) and hafnium (Hf), and their oxides, nitrides and oxynitrides in a composition ratio of less than 20%.

[0132] The configurations of the first and second embodiments of the present invention have been described above, but the present invention is not limited to the configurations of each embodiment. For example, in the present invention, the configurations of the first and second embodiments can be used in combination. Even when the configurations of the first and second embodiments described above are used in combination, the problems of this application can still be solved.

[0133] Example

[0134] Hereinafter, embodiments of the reflective photomask blank and the photomask according to the first embodiment of the present invention will be described using figures and tables.

[0135] [Example 1-1]

[0136] First, use Figure 6 The fabrication method of the reflective photomask blank 100 is explained.

[0137] First, such as Figure 6 As shown, a multilayer reflective film 12, consisting of 40 layers of silicon (Si) and molybdenum (Mo) films stacked together, is formed on a synthetic quartz substrate 11 with low thermal expansion properties. The thickness of the multilayer reflective film 12 is set to 280 nm. Figure 6 For simplicity, the multilayer reflective film 12 is shown as a multi-pair stacked film.

[0138] Next, a capping layer 13 made of ruthenium (Ru) as an intermediate film is formed on the multilayer reflective film 12 with a thickness of 2.5 nm. As a result, a reflective portion 17 having the multilayer reflective film 12 and the capping layer 13 is formed on the substrate 11.

[0139] Next, an absorption layer 14 made of tin oxide (SnO) was formed on the capping layer 13 to a thickness of 25 nm. The atomic ratio of tin (Sn) to oxygen (O) was determined by XPS (X-ray photoelectron spectroscopy), and the result was 1:1.6. It should be noted that since tin (Sn) is chemically stable, bonding with an O / Sn ratio greater than 1 is preferred. In addition, the crystallinity of the absorption layer 14 was determined by XRD (X-ray diffraction), and although slight crystallinity was observed, it was amorphous.

[0140] Next, an outermost layer 15 made of tantalum oxide (TaO) is formed on the absorption layer 14 to a thickness of 2 nm. As a result, a low-reflection portion 18 having the absorption layer 14 and the outermost layer 15 is formed on the reflective portion 17.

[0141] Next, a back conductive film 16 formed of chromium nitride (CrN) with a thickness of 100 nm is formed on the side of the substrate 11 where the multilayer reflective film 12 is not formed, thereby producing the reflective photomask blank 100 of Example 1-1.

[0142] The deposition (layer formation) of each film on the substrate 11 was performed using a multi-element sputtering apparatus. The thickness of each film was controlled by the sputtering time.

[0143] Next, use Figures 7 to 11 The fabrication method of the reflective photomask 200 is explained.

[0144] First, such as Figure 7 As shown, a positive chemical amplification resist (SEBP9012: manufactured by Shin-Etsu Chemical Co., Ltd.) with a film thickness of 120 nm is formed on the low-reflection portion 18 of the reflective photomask blank 100 using a spin coater, and then baked at 110°C for 10 minutes to form a resist film 19.

[0145] Next, a predetermined pattern is drawn on the resist film 19 formed by a positive chemical amplification resist using an electron beam plotter (JBX3030: manufactured by JEOL Ltd.). Then, a baking treatment is performed at 110°C for 10 minutes, followed by spray development (SFG3000: manufactured by SIGMAMELTEC LTD.). Thus, as... Figure 8 As shown, a resist pattern 19a was formed.

[0146] Next, using the resist pattern 19a as an etching mask, the outermost layer 15 is patterned by dry etching primarily using fluorine-based gases, thus achieving the desired pattern. Figure 9 As shown, the outermost pattern is formed on the outermost layer 15.

[0147] Next, the absorption layer 14 is patterned using dry etching primarily employing chlorine-based gases, thus forming the absorption layer pattern. Therefore, as... Figure 10 As shown, a low-reflectivity pattern 18a is formed.

[0148] Next, the residual resist pattern 19a is stripped, thereby revealing... Figure 11 As shown, the reflective photomask 200 involved in this embodiment was fabricated.

[0149] Next, the film was immersed in sulfuric acid at 80°C for 10 minutes, and then immersed in a washing tank containing ammonia, hydrogen peroxide, and water in a 1:1:20 ratio using 500W ultrasonic waves for 10 minutes, followed by 10 minutes of running water to clean it. In this embodiment, the film thickness was measured by AFM and compared with the film thickness at the time of film formation; no change was observed. It should be noted that in this embodiment, the wash resistance required for the photomask is considered to be high for materials and structures where the film reduction is less than 1 nm after the above cleaning process.

[0150] In this embodiment, the low-reflection pattern 18a formed on the low-reflection portion 18 includes: a 64nm LS (linewidth and spacing) pattern on the reflective photomask 200 for transfer evaluation, a 200nm LS pattern for measuring the film thickness of the absorption layer using AFM, and a 4mm square low-reflection removal portion for EUV reflectance measurement. In this embodiment, as... Figure 12 As shown, 64nm linewidth LS patterns are designed in the x and y directions respectively, so that the effect of projection caused by EUV irradiation can be easily observed.

[0151] [Examples 1-2]

[0152] The absorber layer 14 is formed from a homogeneous compound material of tin oxide (SnO) and silicon oxide (SiO) in a 50:50 ratio, and is deposited to achieve a film thickness of 47 nm. Silicon oxide (SiO) has high transparency to EUV light, i.e., it is the compound material with the lowest EUV absorption among the materials in the first group mentioned above, and therefore it was chosen.

[0153] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 1.5 nm. As a result, the total thickness of the low-reflection portion 18 was 48.5 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Examples 1-2 were fabricated using the same method as in Examples 1-1.

[0154] [Examples 1-3]

[0155] The absorber layer 14 is formed from a homogeneous compound material of tin oxide (SnO) and silicon oxide (SiO) in a 50:50 ratio, and is deposited in such a way that its film thickness is 47 nm.

[0156] Next, a molybdenum (Mo) outermost layer 15 was formed on the absorption layer 14 to achieve a film thickness of 13 nm. As a result, the total film thickness of the low-reflection portion 18 was 60 nm. It should be noted that, apart from the film formation of the absorption layer 14 and the outermost layer 15, the reflective photomask preform 100 and reflective photomask 200 of Examples 1-3 were fabricated using the same method as in Examples 1-1.

[0157] [Examples 1-4]

[0158] The absorber layer 14 is formed of tin oxide (SnO) and is deposited in such a way that its thickness is 17 nm.

[0159] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 1.5 nm. As a result, the total thickness of the low-reflection portion 18 was 18.5 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and reflective photomask 200 of Examples 1-4 were fabricated using the same method as in Examples 1-1.

[0160] [Examples 1-5]

[0161] The absorber layer 14 is formed from a homogeneous compound material of tin oxide (SnO) and silicon oxide (SiO) in a 50:50 ratio, and is formed to make the film thickness 35 nm.

[0162] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 1.5 nm. As a result, the total thickness of the low-reflection portion 18 was 36.5 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and reflective photomask 200 of Examples 1-5 were fabricated using the same method as in Examples 1-1.

[0163] [Examples 1-6]

[0164] The absorber layer 14 is formed of tin oxide (SnO) and is deposited in such a way that its thickness is 16 nm.

[0165] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 0.8 nm. As a result, the total thickness of the low-reflection portion 18 was 16.8 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and reflective photomask 200 of Examples 1-6 were fabricated using the same method as in Examples 1-1.

[0166] [Examples 1-7]

[0167] The absorber layer 14 is formed of tin oxide (SnO) and is deposited in such a way that its thickness is 17 nm.

[0168] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 0.8 nm. As a result, the total thickness of the low-reflection portion 18 was 17.8 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and reflective photomask 200 of Examples 1-7 were fabricated using the same method as in Examples 1-1.

[0169] [Comparative Example 1-1]

[0170] The absorption layer 14 is formed of tantalum nitride (TaN) and is deposited to a thickness of 58 nm. The outermost layer 15 is formed of tantalum oxide (TaO) and is deposited to a thickness of 2 nm. This comparative example is assumed to be a conventional reflective photomask with tantalum (Ta) as the main component. It should be noted that, except for the deposition of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Comparative Example 1-1 were fabricated using the same method as in Example 1-1.

[0171] [Comparative Examples 1-2]

[0172] The absorber layer 14 is formed from a homogeneous compound material of tin oxide (SnO) and silicon oxide (SiO) in a ratio of 40:60, and is formed in such a way that its film thickness is 42 nm.

[0173] Next, an outermost layer 15 made of tantalum oxide (TaO) was formed on the absorption layer 14 to a thickness of 1.5 nm. As a result, the total thickness of the low-reflection portion 18 was 43.5 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Comparative Examples 1-2 were fabricated using the same method as in Examples 1-1.

[0174] [Comparative Examples 1-3]

[0175] The absorption layer 14 is formed of tin oxide (SnO) and is deposited such that its thickness is 25 nm. Furthermore, the outermost layer 15 is not formed. It should be noted that, apart from this, the reflective photomask preform 100 and reflective photomask 200 of Comparative Examples 1-3 were fabricated using the same method as in Examples 1-1.

[0176] The reflectivity Rm in the reflective layer region and the reflectivity Ra in the low-reflectivity region of each reflective photomask 200 fabricated in the above-described embodiments and comparative examples were measured using an EUV light reflectivity measuring device. The reflectivity Rm was measured in a 4 mm square absorption layer removal section. Based on the measurement results, the OD value was calculated using the above formula (1).

[0177] (Hydrogen radical resistance)

[0178] like Figure 4 As shown, using a 40MHz CCP (Capacitively Coupled Plasma), a flux of 10 19 at / (cm 2 Hydrogen in sample s) is excited within chamber 300 to generate hydrogen plasma. Hydrogen radical resistance is measured for each sample 302 by placing a reflective photomask 200, fabricated as a sample in the examples and comparative examples, on a single electrode 301 with an inter-electrode distance of 18 mm. The hydrogen radical resistance is measured by confirming the film thickness change of the low-reflectivity portion 18 after hydrogen radical treatment using atomic force microscopy (AFM). Furthermore, the hydrogen radical resistance is measured using a 200 nm linewidth LS pattern.

[0179] (Wafer Exposure Evaluation)

[0180] Using an EUV exposure apparatus (NXE3300B: manufactured by ASML), the low-reflectivity pattern 18a of the reflective photomask 200 prepared in the examples and comparative examples was transferred and exposed onto a semiconductor wafer coated with an EUV positive chemical amplification resist. At this time, the exposure amount was adjusted to... Figure 12 The LS pattern in the x-direction shown is transferred according to the design. Specifically, in this exposure experiment, to make... Figure 12 The LS pattern (64 nm linewidth) in the x-direction shown is exposed as a 16 nm linewidth on the semiconductor wafer. The resolution is confirmed by observing the transferred resist pattern and measuring the linewidth using an electron beam dimensional measuring instrument.

[0181] The evaluation results are shown in Table 3.

[0182] [Table 3]

[0183]

[0184] Table 3, in Comparative Example 1-1, shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 with a tantalum (Ta) based film, wherein the absorption layer 14 is formed of tantalum nitride (TaN) with a film thickness of 58 nm and the outermost layer 15 is formed of tantalum oxide (TaO) with a film thickness of 2 nm. It should be noted that the resist pattern dimensions on the wafer are values ​​recorded as "HV deviation" in the "Pattern Transferability" column.

[0185] In Comparative Example 1-1, the reflective photomask 200 achieved an OD value of 1.5, providing sufficient contrast for pattern transfer. However, patterning using EUV light resulted in a pattern size of 9 nm in the y-direction and an HV deviation (horizontal-vertical size difference) of 7 nm. While development was achieved, the shading effect was significant, leading to low transferability. It should be noted that in this embodiment, conditions with materials and structures having a smaller HV deviation than existing tantalum (Ta)-based films were considered as conditions for improved transferability.

[0186] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of tin oxide (SnO) with a film thickness of 25 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 2 nm, and a low-reflection portion 18.

[0187] In the case of the reflective photomask 200 of Example 1-1, no change in film thickness due to hydrogen radicals was observed, which is a good result. The OD value is 2.0, indicating sufficiently high contrast. The patterning using EUV light resulted in an HV deviation of 4 nm, which is the best result in this evaluation.

[0188] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of a compound material of tin oxide (SnO) and silicon oxide (SiO) (mixing ratio 1:1) with a film thickness of 47 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 1.5 nm, and a low-reflection portion 18.

[0189] In the reflective photomask 200 of Examples 1-2, no change in film thickness due to hydrogen radicals was observed, resulting in good performance. The OD value was 1.7, providing sufficient contrast. Silicon oxide (SiO) is a material with low absorption for EUV light, and the mixing ratio was 1:1, meaning the content of the material from the first material group was 50 atomic%, yet the film thickness was 47 nm with sufficient contrast. The patterning using EUV light resulted in an HV deviation of 5 nm, and compared to Comparative Example 1-1, a reduced shading effect was observed, thus improving pattern transferability.

[0190] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of a compound material of tin oxide (SnO) and silicon oxide (SiO) (mixing ratio 1:1) with a film thickness of 47 nm, an outermost layer 15 formed of molybdenum (Mo) with a film thickness of 13 nm, and a low-reflection portion 18.

[0191] In the reflective photomask 200 of Examples 1-3, no change in film thickness due to hydrogen radicals was observed. The OD value was 1.6, providing sufficient contrast. Patterning using EUV light resulted in pattern transfer with an HV deviation of 6 nm. The combined thickness of the absorption layer 14 and the outermost layer 15 results in a film thickness of 60 nm for the low-reflectivity portion 18. However, the combination of the compound material of the absorption layer 14 and the material of the outermost layer 15 reduces shading effects, thereby improving pattern transferability.

[0192] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of tin oxide (SnO) with a film thickness of 17 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 1.5 nm, and a low-reflection portion 18.

[0193] In the reflective photomask 200 of Examples 1-4, no change in film thickness due to hydrogen radicals was observed. The OD value was 1.0. Patterning using EUV light resulted in an HV deviation of 6 nm, allowing for pattern transfer.

[0194] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of a compound material of tin oxide (SnO) and silicon oxide (SiO) (mixing ratio 1:1) with a film thickness of 35 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 1.5 nm, and a low-reflection portion 18.

[0195] In the reflective photomask 200 of Examples 1-5, no change in film thickness due to hydrogen radicals was observed. The OD value was 1.0. Patterning using EUV light resulted in a pattern transfer with an HV deviation of 6 nm. Based on this result, it can be seen that when the content of the first material group is set to 50 atomic percent in the absorber layer 14, its film thickness can be as thin as 35 nm.

[0196] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of tin oxide (SnO) with a film thickness of 16 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 0.8 nm, and a low-reflection portion 18.

[0197] In the reflective photomask 200 of Examples 1-6, a slight variation in film thickness was observed due to hydrogen radicals. The outermost layer 15 became thinner, making uniform film formation impossible, and a selective reduction in the absorption layer was observed due to uneven film formation. The OD value was 0.99, which is insufficient contrast for transfer. Patterning using EUV light resulted in an HV deviation of 6 nm, allowing for pattern transfer, but the line edge roughness increased due to insufficient contrast.

[0198] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of tin oxide (SnO) with a film thickness of 17 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 0.8 nm, and a low-reflection portion 18.

[0199] In the reflective photomask 200 of Examples 1-7, similar to Examples 1-6, a slight change in film thickness due to hydrogen radicals was observed. The OD value was 1.0. Patterning using EUV light resulted in an HV deviation of 6 nm, allowing for pattern transfer. Due to the higher contrast compared to Examples 1-6, no degradation in line edge roughness was observed.

[0200] In Table 3, in Comparative Examples 1-2, the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of a compound material of tin oxide (SnO) and silicon oxide (SiO) (mixing ratio 2:3) with a film thickness of 42 nm, an outermost layer 15 formed of tantalum oxide (TaO) with a film thickness of 1.5 nm, and a low-reflection portion 18 are shown.

[0201] In Comparative Examples 1-2, the reflective photomask 200 had an OD value of 1.0. Patterning using EUV light resulted in no transfer in the y-direction. When the content of the first material group was less than 50 atomic percent, sufficient contrast could not be obtained without increasing the thickness of the absorption layer 14; furthermore, increasing the thickness to obtain contrast increased the projection effect, leading to deterioration in transferability. It should be noted that hydrogen radical resistance was not evaluated.

[0202] Table 3 shows the mask properties and resist pattern dimensions on the wafer of a reflective photomask 200 having an absorption layer 14 formed of tin oxide (SnO) with a film thickness of 25 nm and no outermost layer 15.

[0203] In Comparative Examples 1-2, the reflective photomask 200 achieved an OD value of 1.7, resulting in sufficient contrast. Patterning using EUV light resulted in an HV deviation of 4 nm, achieving high transferability. However, hydrogen radical resistance evaluation revealed a change in film thickness before and after treatment.

[0204] It should be noted that in Table 3, for each evaluation result, cases evaluated as having excellent characteristics are marked with "○"; cases evaluated as having characteristics that have no problems in use are marked with "△"; and cases evaluated as having characteristics that have problems in use are marked with "×".

[0205] When comparing Examples 1-1 to 1-5 with existing films (Comparative Example 1-1), it is evident that the hydrogen radical resistance is comparable, and the pattern transferability is improved. Furthermore, when comparing Examples 1-1 to 1-7 with Comparative Example 1-3, it is evident that the hydrogen radical resistance of the low-reflection portion 18, which is formed from a material comprising at least one of the second material groups, is improved compared to the low-reflection portion 18 formed solely from the absorption layer 14.

[0206] Furthermore, in any of the reflective photomasks 200 of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3 in Table 3, the film thickness did not change before and after the cleaning process, and high cleaning resistance was obtained in all cases.

[0207] Therefore, it can be seen that the reflective photomask 200 obtained by forming an outermost layer 15 of a compound material composed of a second material group with a content of 80% or more on an absorption layer 14 of a compound material composed of a first material group with a content of 50% or more is a reflective photomask with excellent transferability and hydrogen radical resistance, reduced projection effect, long life and high transfer performance.

[0208] Hereinafter, embodiments of the reflective photomask blank and the reflective photomask according to the second embodiment of the present invention will be described.

[0209] [Example 2-1]

[0210] like Figure 6 As shown, a multilayer reflective film 12, consisting of 40 layers of silicon (Si) and molybdenum (Mo) stacked together, is formed on a synthetic quartz substrate 11 with low thermal expansion properties. The thickness of the multilayer reflective film 12 is set to 280 nm.

[0211] Next, a capping layer 13 made of ruthenium (Ru) as an intermediate film is formed on the multilayer reflective film 12 with a thickness of 2.5 nm. As a result, a reflective portion 17 having the multilayer reflective film 12 and the capping layer 13 is formed on the substrate 11.

[0212] Next, an absorption layer 14 was formed on the capping layer 13 by depositing a homogeneous material of indium oxide and germanium in a ratio of 30:70, resulting in a film thickness of 47 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy), and the result was 1:1.5. In addition, the crystallinity of the absorption layer 14 was determined by XRD (X-ray diffraction), and the result was amorphous.

[0213] Next, an outermost layer 15 made of tantalum oxide is formed on the absorption layer 14 to a thickness of 2 nm. As a result, a low-reflection portion 18 having the absorption layer 14 and the outermost layer 15 is formed on the reflective portion 17.

[0214] Next, a back conductive film 16 formed of chromium nitride is formed on the side of the substrate 11 where the multilayer reflective film 12 is not formed, with a thickness of 100 nm, thereby producing the reflective photomask blank 100 of Example 2-1.

[0215] The films on the substrate 11 were formed using a multi-element sputtering apparatus. The thickness of each film was controlled by the sputtering time.

[0216] Next, use Figures 7 to 11 The fabrication method of the reflective photomask 200 is explained.

[0217] like Figure 7 As shown, a positive chemical amplification resist (SEBP9012: manufactured by Shin-Etsu Chemical Co., Ltd.) with a film thickness of 120 nm is formed on the low-reflection portion 18 of the reflective photomask blank 100 using a spin coater, and then baked at 110°C for 10 minutes to form a resist film 19.

[0218] Next, a predetermined pattern is drawn on the resist film 19 formed by a positive chemical amplification resist using an electron beam plotter (JBX3030: manufactured by JEOL Ltd.). Then, a baking treatment is performed at 110°C for 10 minutes, followed by spray development (SFG3000: manufactured by SIGMAMELTEC LTD.). Thus, as... Figure 8 As shown, a resist pattern 19a was formed.

[0219] Next, using the resist pattern 19a as an etching mask, the outermost layer 15 is patterned by dry etching primarily using fluorine-based gases, thus achieving the desired pattern. Figure 9 As shown, the outermost pattern is formed on the outermost layer 15.

[0220] Next, the absorption layer 14 is patterned using dry etching primarily with chlorine-based gases, thus forming an absorption pattern. Therefore, as... Figure 10 As shown, a low-reflectivity pattern 18a is formed.

[0221] Next, the residual resist pattern 19a is stripped, thereby revealing... Figure 11 As shown, the reflective photomask 200 involved in this embodiment was fabricated.

[0222] Next, the reflective photomask 200 involved in this embodiment was immersed in sulfuric acid at 80°C for 10 minutes, and then immersed in a cleaning tank filled with a cleaning solution composed of ammonia, hydrogen peroxide, and water in a ratio of 1:1:20, using 500W ultrasonic wave for 10 minutes, followed by running water for 10 minutes for cleaning. Then, the film thickness was measured using atomic force microscopy (AFM) and compared with the film thickness at the time of film formation; no change was observed.

[0223] In this embodiment, the low-reflection pattern 18a formed on the low-reflection portion 18 includes: a 64nm LS (linewidth and spacing) pattern on the reflective photomask 200 for transfer evaluation, a 200nm LS pattern for measuring the film thickness of the absorption layer 14 using AFM, and a 4mm square low-reflection removal portion for EUV reflectance measurement. Figure 12 As shown, 64nm linewidth LS patterns are designed in the x and y directions respectively, so that the effect of projection caused by EUV tilt irradiation can be easily observed.

[0224] [Example 2-2]

[0225] The absorber layer 14 is formed from a homogeneous material of indium oxide and germanium in a 50:50 ratio, and is deposited to achieve a film thickness of 47 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy) and found to be 1:1.5.

[0226] Next, an outermost layer 15 made of tantalum oxide was formed on the absorption layer 14 to a thickness of 2 nm. As a result, the total thickness of the low-reflection portion 18 was 49 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Example 2-2 were fabricated using the same method as in Example 2-1.

[0227] [Examples 2-3]

[0228] The absorber layer 14 is formed from a homogeneous material of indium oxide and germanium in a 50:50 ratio, and is deposited to achieve a film thickness of 33 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy) and the result was 1:1.5.

[0229] Next, an outermost layer 15 made of tantalum oxide was formed on the absorption layer 14 to achieve a film thickness of 2 nm. As a result, the total film thickness of the low-reflection portion 18 was 35 nm. It should be noted that, apart from the film formation of the absorption layer 14 and the outermost layer 15, the reflective photomask preform 100 and the reflective photomask 200 of Examples 2-3 were fabricated using the same method as in Example 2-1.

[0230] [Examples 2-4]

[0231] The absorber layer 14 is formed of indium oxide and is deposited in such a way that its thickness is 26 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy) and the result was 1:1.5.

[0232] Next, an outermost layer 15 made of tantalum oxide was formed on the absorption layer 14 to a thickness of 2 nm. As a result, the total thickness of the low-reflection portion 18 was 28 nm. It should be noted that, apart from the formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Examples 2-4 were fabricated using the same method as in Example 2-1.

[0233] [Examples 2-5]

[0234] The absorber layer 14 is formed of indium oxide and is deposited in such a way that its thickness is 26 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy) and the result was 1:1.5.

[0235] Next, a bismuth (Bi) outermost layer 15 was formed on the absorption layer 14 to achieve a film thickness of 2 nm. As a result, the total film thickness of the low-reflection portion 18 was 28 nm. It should be noted that, apart from the film formation of the absorption layer 14 and the outermost layer 15, the reflective photomask preform 100 and the reflective photomask 200 of Examples 2-5 were fabricated using the same method as in Examples 2-1.

[0236] [Comparative Example 2-1]

[0237] The absorber layer 14 is formed of indium oxide and is deposited to a thickness of 26 nm. The atomic ratio of indium to oxygen was determined by XPS (X-ray photoelectron spectroscopy) and the result was 1:1.5. Furthermore, the outermost layer 15 was not formed. It should be noted that, apart from this, the reflective photomask preform 100 and the reflective photomask 200 of Comparative Example 2-1 were fabricated using the same method as in Example 2-1.

[0238] [Comparative Example 2-2]

[0239] The absorption layer 14 is formed of tantalum nitride and is formed to have a film thickness of 58 nm. In addition, the outermost layer 15 is formed of tantalum oxide (TaO) and is formed to have a film thickness of 2 nm. This comparative example is assumed to be a reflective photomask of a conventional existing film mainly composed of tantalum. Note that, except for the film formation of the absorption layer 14 and the outermost layer 15, the reflective photomask blank 100 and the reflective photomask 200 of Comparative Example 2-2 were fabricated by the same method as in Example 2-1.

[0240] The reflectance Rm of the reflective layer region and the reflectance Ra of the low reflectance portion region of the reflective photomask 200 fabricated in the above-described examples and comparative examples were measured using a reflectance measurement apparatus using EUV light. The measurement of the reflectance Rm was performed in a 4 mm square absorption layer removal portion. Based on the measurement results, the OD value was calculated using the above formula (1).

[0241] (Hydrogen radical resistance)

[0242] The reflective photomasks 200 fabricated in the examples and comparative examples were placed in a hydrogen radical environment using microwave plasma at a power of 1 kW and a hydrogen pressure of 0.36 mbar or less. The change in the film thickness of the absorption layer 4 after the hydrogen radical treatment was confirmed using AFM. The measurement was performed using a 200 nm LS pattern with a line width.

[0243] At this time, regarding the hydrogen radical resistance, the case where the film reduction rate is 0.1 nm / s or less was evaluated as "○", and the particularly excellent case was evaluated as "◎". In addition, the case where there is a film reduction of several nm just after the start of the hydrogen radical treatment, but the subsequent film reduction rate is 0.1 nm / s or less was evaluated as "△"; the case where the film reduction rate all exceeds 0.1 nm / s was evaluated as "×". Note that, in this example, if the evaluation is "○" or above, there is no problem in use and it is qualified.

[0244] (Wafer exposure evaluation)

[0245] Using an EUV exposure apparatus (NXE3300B: manufactured by ASML), the low reflectance portion pattern 18a of the reflective photomask 200 fabricated in the examples and comparative examples was transferred and exposed onto a semiconductor wafer coated with an EUV positive chemically amplified resist. At this time, the exposure amount was adjusted so that Figure 12 the LS pattern in the x direction was transferred as designed. Then, the transferred resist pattern was observed using an electron beam size measuring instrument and the line width was measured to confirm the resolution.

[0246] At this time, regarding the HV-deviation, the 7.3 nm of the existing film is set as "△"; if it is less than 7.3 nm, it is set as "○"; if it is 4.5 nm or less, it is set as "◎". Regarding the OD value, if it is 1.5 or more, it is set as "○"; if it is 2 or more, it is set as "◎". It should be noted that regarding the HV-deviation, if the evaluation is "△" or more, there is no problem in use and it is qualified. In addition, regarding the OD value, if the evaluation is "○" or more, there is no problem in use and it is qualified.

[0247] These evaluation results are shown in Table 4.

[0248] [Table 4]

[0249]

[0250] In Table 4, in Comparative Example 2-2, the mask characteristics of the Ta-based existing film in which the absorption layer 14 is formed of tantalum nitride with a film thickness of 58 nm and the outermost layer 15 is formed of tantalum oxide with a film thickness of 2 nm and the resist pattern size on the wafer are shown. In the case of the reflective photomask 200 of Comparative Example 2-2, the OD value is 1.54, and a contrast that enables pattern transfer can be obtained. As a result of patterning using EUV light, the H-V deviation (horizontal-vertical dimension difference) becomes 7.3 nm. Although development is possible, the influence of the shadow effect is large, resulting in low transferability.

[0251] In Table 4, in Example 2-1, the mask characteristics of the photomask in which the absorption layer 14 is formed of a material composed of indium oxide and germanium (mixing ratio 30:70) with a film thickness of 47 nm and the outermost layer 15 is formed of tantalum oxide with a film thickness of 2 nm and the resist pattern size on the wafer are shown. In the case of the reflective photomask 200 of Example 2-1, no change in film thickness due to hydrogen radicals was observed, resulting in good results. The OD value is 1.73, and a contrast that enables pattern transfer can be obtained. As a result of patterning using EUV light, the H-V deviation becomes 5.3 nm, and excellent pattern transferability is obtained compared to Comparative Example 2-2.

[0252] In Table 4, in Example 2-2, the mask characteristics of the photomask in which the absorption layer 14 is formed of a material composed of indium oxide and germanium (mixing ratio 50:50) with a film thickness of 47 nm and the outermost layer 15 is formed of tantalum oxide with a film thickness of 2 nm and the resist pattern size on the wafer are shown. In the case of the reflective photomask 200 of Example 2-2, no change in film thickness due to hydrogen radicals was observed, resulting in good results. The OD value is 2.33, and a higher contrast than that of Example 2-1 is obtained. As a result of patterning using EUV light, the H-V deviation becomes 7.0 nm. Compared to Comparative Example 2-2, a result with reduced shadow effect and improved pattern transferability is obtained, but the performance is slightly worse than that of Example 2-1.

[0253] Table 4 shows the mask properties and resist pattern dimensions on the wafer for photomasks in Examples 2-3, where the absorption layer 14 is formed of a material composed of indium oxide and germanium (mixing ratio 50:50) with a film thickness of 33 nm, and the outermost layer 15 is formed of tantalum oxide with a film thickness of 2 nm. In the reflective photomask 200 of Examples 2-3, no change in film thickness due to hydrogen radicals was observed, resulting in good performance. The OD value was 1.55, providing sufficient contrast for pattern transfer. Patterning using EUV light resulted in an HV deviation of 4.1 nm. Compared to Comparative Example 2-2, this resulted in reduced shading effects and significantly improved pattern transferability. Compared to Example 2-2, it was found that using a thinner film improved both the OD value and the HV deviation.

[0254] Table 4 shows the mask properties and resist pattern dimensions on the wafer for photomasks in Examples 2-4, where the absorption layer 14 is formed of indium oxide with a thickness of 26 nm and the outermost layer 15 is formed of tantalum oxide with a thickness of 2 nm. In the reflective photomask 200 of Examples 2-4, no change in film thickness due to hydrogen radicals was observed. An OD value of 1.77 was obtained, resulting in a contrast suitable for pattern transfer. Patterning using EUV light resulted in an HV deviation of 4.6 nm, indicating reduced shading effects and significantly improved pattern transferability compared to Comparative Example 2-2.

[0255] Table 4 shows the mask properties and resist pattern dimensions on the wafer for photomasks in Examples 2-5, where the absorption layer 14 is formed of indium oxide with a thickness of 26 nm and the outermost layer 15 is formed of bismuth (Bi) with a thickness of 2 nm. In the reflective photomask 200 of Examples 2-5, no change in film thickness due to hydrogen radicals was observed. An OD value of 1.77 was obtained, providing sufficient contrast for pattern transfer. Patterning using EUV light resulted in an HV deviation of 4.6 nm, indicating reduced shading effects and significantly improved pattern transferability compared to Comparative Example 2-2.

[0256] Table 4 shows the mask properties and resist pattern dimensions on the wafer in Comparative Example 2-1, where the absorption layer 14 is formed of indium oxide (O / In = 1.5) with a film thickness of 26 nm and the outermost layer 15 is not formed. With the reflective photomask 200 in Comparative Example 2-1, the OD value is 1.77, resulting in sufficient contrast. Patterning using EUV light resulted in an HV deviation of 4.6 nm, achieving high transferability. However, the hydrogen radical resistance evaluation showed a film reduction of 1 nm immediately after the hydrogen radical treatment began, after which no further film reduction was observed.

[0257] When comparing Examples 2-1 to 2-5 with existing films (Comparative Example 2-2), the hydrogen radical resistance of each reflective photomask 200 in Examples 2-1 to 2-5 is equal to or greater than that of reflective photomasks using existing films, thus improving pattern transferability. Furthermore, a comparison with Comparative Example 2-1 shows that the low-reflection portion 18 formed by using a hydrogen radical-resistant material as the main material, which forms the outermost layer 15, has higher hydrogen radical resistance than a low-reflection portion 18 formed solely by the absorption layer 14.

[0258] In addition, in any of the reflective photomasks 200 of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2 shown in Table 4, the film thickness did not change before and after the cleaning process, and all of them obtained results with cleaning resistance.

[0259] Therefore, it can be seen that a reflective photomask 200 obtained by forming an outermost layer 15 made of a material resistant to hydrogen radicals on an absorption layer 14 made of a material with a high k-value is a photomask with excellent transferability and irradiation resistance, reduced projection effect, long lifetime, and high transfer performance. In other words, if a reflective photomask 200 is obtained by having an outermost layer 15 made of a material resistant to hydrogen radicals on an absorption layer 14 containing a material with a high k-value, the projection effect can be suppressed or mitigated, and it is resistant to hydrogen radicals.

[0260] Industrial applicability

[0261] The reflective photomask blank and reflective photomask of the present invention can be used to form fine patterns by EUV exposure in the manufacturing process of semiconductor integrated circuits and the like.

[0262] Explanation of symbols

[0263] 1...Substrate

[0264] 2…Multilayer reflective film

[0265] 3…Capping layer

[0266] 4…Absorption layer

[0267] 5…outermost layer

[0268] 7…Reflector

[0269] 8…Low-reflection section

[0270] 8a… Low-reflectivity pattern

[0271] 10…Reflective photomask preform

[0272] 20…Reflective photomask

[0273] 11…Substrate

[0274] 12…Multilayer reflective film

[0275] 13…Capping layer

[0276] 14…Absorption Layer

[0277] 15…outermost layer

[0278] 16… Backside conductive film

[0279] 17…Reflector

[0280] 18…Low-reflection section

[0281] 18a… Low-reflectivity pattern

[0282] 19…Resist film

[0283] 19a…Resist pattern

[0284] 100…Reflective photomask preform

[0285] 200…reflective photomask

[0286] 300… chambers

[0287] 301…electrode

[0288] 302…sample

Claims

1. A reflective photomask preform for fabricating a reflective photomask for pattern transfer using extreme ultraviolet light as a light source, characterized in that it comprises: substrate, A reflective portion formed on the substrate and reflecting incident light, and A low-reflectivity portion formed on the reflective portion and absorbing incident light. The low-reflection portion is a stacked structure consisting of at least two layers, namely an absorption layer and an outermost layer. At least one layer of the absorber layer contains at least one material selected from the first material group, comprising a total atomic percentage of 50% or more. The outermost layer contains at least one material selected from the second material group, totaling more than 80 atomic percent. The first group of materials includes tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn), and bismuth (Bi), as well as their oxides, nitrides, and oxynitrides. The second group of materials consists of aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn), and vanadium (V), as well as their oxides, nitrides, and oxynitrides.

2. The reflective photomask preform according to claim 1, characterized in that, The film thickness of the low-reflectivity portion is less than 60 nm. Even when the absorption layer is divided into multiple layers, the total film thickness of each layer is between 17 nm and 47 nm. The outermost film has a thickness of 1 nm or more.

3. The reflective photomask blank according to claim 2, characterized in that, Even when the absorption layer is divided into multiple layers, the total film thickness of each layer is between 17 nm and 45 nm.

4. The reflective photomask preform according to claim 1 or claim 2, characterized in that, The total thickness of the absorption layer is in the range of 17 nm to 47 nm, and the OD value (Optica Density) is 1.0 or higher.

5. A reflective photomask for pattern transfer using extreme ultraviolet light as a light source, characterized in that it comprises: substrate, A reflective portion formed on the substrate and reflecting incident light, and A low-reflectivity portion formed on the reflective portion and absorbing incident light. The low-reflection portion is a stacked structure consisting of at least two layers, namely an absorption layer and an outermost layer. At least one layer of the absorber layer contains at least one material selected from the first material group, comprising a total atomic percentage of 50% or more. The outermost layer contains at least one material selected from the second material group, totaling more than 80 atomic percent. The first group of materials includes tin (Sn), tellurium (Te), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), copper (Cu), zinc (Zn), and bismuth (Bi), as well as their oxides, nitrides, and oxynitrides. The second group of materials consists of aluminum (Al), ruthenium (Ru), molybdenum (Mo), zirconium (Zr), titanium (Ti), zinc (Zn), and vanadium (V), as well as their oxides, nitrides, and oxynitrides.

6. The reflective photomask according to claim 5, characterized in that, The film thickness of the low-reflectivity portion is less than 60 nm. Even when the absorption layer is divided into multiple layers, the total film thickness of each layer is between 17 nm and 47 nm. The outermost film has a thickness of 1 nm or more.

7. The reflective photomask according to claim 6, characterized in that, Even when the absorption layer is divided into multiple layers, the total film thickness of each layer is between 17 nm and 45 nm.

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