Reflective photomask blank and reflective photomask

Abstract

The present invention provides a reflective photomask blank and a reflective photomask having good radiation resistance and good transfer performance. The reflective photomask blank (10) has a reflective layer (2) for reflecting incident light and an absorption layer (4) for absorbing incident light formed in sequence on one surface of a substrate (1). The absorption layer (4) contains, at least in the outermost layer: a first material selected from the group of tin, indium, and tellurium, and a second material composed of one or more materials selected from the group of transition metals, bismuth, and silicon. The content of the second material in the same layer is greater than 20 atomic % and less than 50 atomic %.

Description

Technical Field

[0001] The present invention relates to a reflective photomask blank and a reflective photomask, and is particularly suitable for EUV photomasks. Background Art

[0002] In the manufacturing process of semiconductor devices, as semiconductor devices become more miniaturized, the requirements for miniaturization of photolithography technology also increase accordingly. In photolithography, the minimum resolution size of the transferred pattern depends greatly on the wavelength of the exposure light source. The shorter the wavelength, the smaller the minimum resolution size. Therefore, in the manufacturing process of semiconductor devices, the exposure light source used is converted from the traditional ArF excimer laser with a wavelength of 193nm to an exposure light source in the extreme ultraviolet (EUV) region with a wavelength of 13.5nm.

[0003] However, almost all substances have high light absorption with respect to light in the EUV region. Therefore, unlike conventional transmission-type photomasks, the photomask for EUV exposure (EUV photomask) is a reflective photomask (for example, refer to Patent Document 1). Patent Document 1 discloses that in a reflective exposure mask for EUV lithography, a multilayer film formed by periodically stacking two or more material layers is formed on a lower substrate, and a mask pattern composed of a nitrogen-containing metal film or a mask pattern composed of a stacked structure of a metal nitride film and a metal film is formed on the multilayer film.

[0004] In addition, as described above, EUV lithography cannot use a refractive optical system that utilizes the transmission of light, so the optical system components of the exposure instrument use mirrors instead of lenses. Therefore, there is a problem that the incident light and reflected light used for EUV lithography cannot be set on the same axis. In EUV lithography, for example, the following method is used: the optical axis is tilted 6 degrees in the vertical direction relative to the EUV photomask surface to allow the EUV light to be incident, and the reflected light reflected at an angle of minus 6 degrees is guided to the semiconductor substrate.

[0005] Thus, the optical axis is tilted in EUV lithography, and therefore, EUV light incident on the EUV photomask casts a shadow of the mask pattern (absorption layer pattern) of the EUV photomask, which may cause a problem called a shadow effect in which transfer performance is deteriorated.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2001-237174 Summary of the invention

[0009] Problems to be Solved by the Invention

[0010] In addition, in the conventional EUV exposure device, in order to prevent the exhaust gas components from the resist coated on the wafer during EUV exposure from contaminating the device, the device is set to a hydrogen radical atmosphere. Therefore, the EUV photomask needs to have durability (irradiation resistance) against EUV irradiation in a hydrogen radical atmosphere to prevent damage to the absorption layer due to the reaction with the hydrogen radicals.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a reflective photomask blank and a reflective photomask that have excellent radiation resistance and can obtain excellent transfer performance.

[0012] Means for solving problems

[0013] In order to solve the problem, a reflective photomask blank as one embodiment of the present invention has a reflective layer for reflecting incident light and an absorption layer for absorbing incident light formed in sequence on one surface of a substrate, wherein the absorption layer contains, at least in its outermost layer: a first material selected from the group of tin, indium, and tellurium; and a second material composed of one or more materials selected from the group of transition metals, bismuth (Bi), and silicon (Si), characterized in that the content of the second material in the same layer is greater than 20 atomic % and less than 50 atomic %.

[0014] In addition, as one embodiment of the present invention, a reflective photomask comprises: a reflective layer formed on one surface of a substrate and reflecting incident light, and an absorption layer on the reflective layer absorbing the incident light and forming a predetermined pattern, wherein the absorption layer contains, at least in its outermost layer: a first material selected from the group consisting of tin, indium, and tellurium; and a second material consisting of one or more materials selected from the group consisting of transition metals, bismuth (Bi), and silicon (Si), characterized in that the content of the second material in the same layer is greater than 20 atomic % and less than 50 atomic %.

[0015] Effects of the Invention

[0016] According to the method of the present invention, the radiation resistance during EUV exposure can be improved, thereby extending the life of the reflective photomask. In addition, according to the method of the present invention, even if the absorption film is thinned, it can have high EUV light absorption, so the influence of the projection effect is alleviated, and the resolution of the pattern transferred to the wafer can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0019] [ Figure 3 ] is a graph showing the optical constants of various metal materials at the wavelength of EUV light.

[0020] [ Figure 4 ] is a graph showing simulation results of the reflectivity of a reflective photomask blank containing tin in the absorption layer under EUV light.

[0021] [ Figure 5 ] is a graph showing simulation results of the OD value of a reflective photomask blank containing tin in the absorption layer at the wavelength of EUV light.

[0022] [ Figure 6 ] is a graph showing simulation results of the reflectivity of a reflective photomask blank containing indium in the absorption layer under EUV light.

[0023] [ Figure 7 ] is a graph showing simulation results of the OD value of a reflective photomask blank containing indium in the absorption layer at the wavelength of EUV light.

[0024] [ Figure 8 ] is a graph showing simulation results of the reflectivity of a reflective photomask blank containing tellurium in the absorption layer under EUV light.

[0025] [ Fig. 9 ] is a graph showing simulation results of the OD value of a reflective photomask blank containing tellurium in the absorption layer at the wavelength of EUV light.

[0026] [ Fig.10 ] is a schematic cross-sectional view showing the structure of a reflective photomask blank in an embodiment.

[0027] [ Fig.11 ] is a schematic cross-sectional view showing the manufacturing process of the reflective photomask in the embodiment.

[0028] [ Fig.12 ] is a schematic cross-sectional view showing the manufacturing process of the reflective photomask in the embodiment.

[0029] [ Fig.13 ] is a schematic cross-sectional view showing the structure of a reflective photomask in an embodiment. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0031] It should be noted that each figure is a schematic diagram, and the size and shape of each part are appropriately exaggerated for easy understanding. In addition, in order to simplify the description, the same symbols are attached to the corresponding parts of each figure.

[0032] (Reflective Photomask Blank)

[0033] The reflective photomask blank according to the present embodiment is a photomask blank for forming a reflective photomask that reflects EUV light and irradiates the reflected light onto a transfer sample.

[0034] like Figure 1 As shown, a reflective photomask blank 10 of the present embodiment includes a substrate 1 , a reflective layer 2 stacked on the substrate 1 , and an absorption layer 4 stacked on the reflective layer 2 .

[0035] The reflective layer 2 is a layer that reflects incident light. Figure 1 The reflective layer 2 shown includes a multilayer reflective layer 2a and an intermediate layer 2b having a multilayer structure.

[0036] The absorption layer 4 is a layer that absorbs incident light and has a single-layer structure or a laminated structure in which a plurality of layers are laminated.

[0037] (Reflective Photomask)

[0038] like Figure 2 As shown, the reflective photomask 20 according to the present embodiment is obtained by forming the absorption layer 4 of the reflective photomask blank 10 on a predetermined absorption layer pattern 4a.

[0039] like Figure 2 As shown, the reflective photomask 20 includes a substrate 1 , a reflective layer 2 stacked on the substrate 1 , and an absorption layer 4 formed on the reflective layer 2 .

[0040] As described above, the reflective layer 2 is a layer that reflects incident light. Figure 2 The reflective layer 2 shown includes a multilayer reflective layer 2a and an intermediate layer 2b having a multilayer structure.

[0041] The absorption layer 4 is a layer that absorbs incident light and has a predetermined absorption layer pattern 4a formed therein. The absorption layer 4 has a single layer structure or a laminated structure in which a plurality of layers are laminated.

[0042] (Absorbent layer)

[0043] The absorption layer 4 contains, at least in the outermost layer, a first material selected from the group consisting of tin, indium, and tellurium, and a second material consisting of one or more materials selected from the group consisting of transition metals, bismuth (Bi), and silicon (Si).

[0044] The first material is composed of any one of the above-mentioned tin, indium, and tellurium. The content of the first material can be determined according to the value of the attenuation coefficient k required by the absorption layer 4. For example, as an attenuation coefficient k that can well maintain the photolithography characteristics, when 0.052 or more is set as the required value, the first material in the same layer (per unit volume) needs to contain: when the first material is tin (Sn), it is 17 atomic % or more, when the first material is indium (In), it is 21 atomic % or more, and when the first material is tellurium (Te), it is 17 atomic % or more.

[0045] The content of the second material in the same layer (per unit volume) is set to be greater than 20 atomic % and less than 50 atomic %.

[0046] In addition, in consideration of the processability and heat resistance of the reflective photomask blank 10 , the absorption layer 4 preferably contains oxygen at least in the outermost layer.

[0047] At this time, the ratio (B / A) of the number of atoms (B) of the second material to the total number of atoms (A) which is the sum of the number of atoms of the first material and the number of oxygen atoms contained in the absorption layer 4 is preferably in a range of greater than 1 / 4 and less than 1. Here, the "contained oxygen" is included as an oxide of the first material or the second material. The "contained oxygen" may also be included only as an oxide of the first material.

[0048] Considering that the transfer performance can be improved by thinning, the thickness of the absorption layer 4 is preferably 18 nm or more and less than 45 nm, and more preferably 18 nm or more and less than 35 nm.

[0049] Here, by removing a portion of the absorption layer 4 of the reflective photomask blank 10, the absorption layer pattern 4a as the reflective photomask 20 can be formed. At this time, in EUV lithography, the incident light obliquely incident on the reflective photomask forms a projection of the absorption layer pattern on the reflective layer, so that the transfer performance to the wafer is deteriorated. By reducing the thickness of the absorption layer 4, the deterioration of the transfer performance can be alleviated.

[0050] In addition, the intensity of the reflected light from the reflective layer 2 is denoted as Rm, and the intensity of the reflected light from the absorbing layer 4 is denoted as Ra (refer to Figure 2 ), the optical density OD based on the reflective layer 2 and the absorption layer 4 is defined by the following formula (1), and in this case, the value of the optical density OD is preferably greater than 1. The value of the optical density OD is not particularly limited as long as it is greater than 1, but considering the thin film of the absorption layer 4, the value of the optical density OD is set to be less than 2, for example.

[0051] OD=-log(Ra / Rm)···(1)

[0052] In addition, in the present embodiment, the absorption layer 4 contains the first material having a larger attenuation coefficient k than the conventional absorption layer as described above. Therefore, in the present embodiment, it is possible to achieve a thin film while maintaining the absorption performance.

[0053] <About the first material>

[0054] Figure 3 It is a graph showing the optical constants of various metal materials at the wavelength of EUV light. Figure 3 The horizontal axis represents the refractive index n, and the vertical axis represents the attenuation coefficient k.

[0055] like Figure 3 As shown, materials with high attenuation coefficients k include silver (Ag), nickel (Ni), tin (Sn), tellurium (Te), indium (In), etc. The attenuation coefficients of these metal materials are in the range of 0.07 to 0.08, which is greater than the attenuation coefficient of 0.041 of tantalum (Ta), a traditional absorption layer material.

[0056] Therefore, in this embodiment, by making the absorption layer 4 contain the first material (tin (Sn), tellurium (Te), indium (In)) having a large attenuation coefficient, it is possible to achieve a thin film of the absorption layer 4 while maintaining the absorption performance. Then, in this embodiment, by thinning, it is possible to suppress the degradation of the transfer performance.

[0057] The first material is usually contained in the absorption layer 4 in the form of an oxide of the first material (tin oxide containing tin and oxygen, etc.). However, it has been confirmed that absorption performance can be maintained and thin film can be achieved even in the oxide state (see Examples).

[0058] Here, the oxygen contained in the absorption layer 4 is contained in the absorption layer 4 not only in the form of oxidation of the first material but also in the form of oxidation of the second material.

[0059] <About optical density OD>

[0060] In addition, as one of the indices representing the basic performance of a reflective photomask, there is the above-mentioned optical density (OD).

[0061] Figure 4 These are the results of a simulation of the EUV light reflectivity in the absorption layer region containing tin. Figure 5 Yes Figure 4 The result is obtained by simulating the OD value in .

[0062] As simulation conditions, the photomask structure was set to the following layer structure: below the absorption layer 4 was a capping layer (intermediate layer 2b) made of ruthenium (Ru) with a thickness of 2.5 nm; below the capping layer was a multilayer reflection layer 2a formed by stacking 40 pairs of stacked films with silicon and molybdenum as a pair; below the multilayer reflection layer 2a was a flat substrate 1 made of synthetic quartz; on the back of the substrate 1 was a back conductive layer made of chromium nitride (CrN). Two types of tantalum film and tin oxide film with a tantalum content of 30 atomic % were used as the absorption layer 4. The refractive index of the tantalum film was 0.94 and the attenuation coefficient was 0.041. The refractive index of the tin oxide film with a tantalum content of 30 atomic % was 0.93 and the attenuation coefficient was 0.062.

[0063] Depend on Figure 4 It can be seen that, compared with the case where the tantalum film is used as the absorption layer 4, when the tantalum film is used as the absorption layer 4, for example, when the absorption layer 4 has the same thickness, the EUV light reflectivity can be greatly reduced. In addition, it can be seen that when the reflectivity is the same, the film thickness can be greatly reduced. Therefore, it is effective to use the tantalum-containing tin oxide film as a constituent element of the high absorption layer at the wavelength of EUV light.

[0064] In addition, by Figure 5 It can be seen that in order to obtain an OD value of 1 or more, the tantalum film needs to have a film thickness of at least 40 nm, while in the case of a tantalum-containing tin oxide film, the film thickness can be less than half, that is, about 18 nm. From this, it can be seen that from the viewpoint of OD value, it is effective to use a tantalum-containing tin oxide film as a component that can reduce the thickness of the entire absorption layer compared to a tantalum film.

[0065] In addition, in order to obtain an OD value of 2 or more, in the case of a tantalum film, a film thickness of at least 70 nm is required, while in the case of a tantalum-containing tin oxide film, a film thickness of 33 nm is sufficient. It can be seen from this that, compared with a tantalum film, even at an OD value of 2 or more, using a tantalum-containing tin oxide film as a component capable of reducing the thickness of the entire absorption layer 4 is effective. It should be noted that in conventional absorption layers, a tantalum film with a film thickness of about 70 nm (OD value of 2) is used as a standard.

[0066] Therefore, by using a tantalum-containing tin oxide film for the absorption layer 4 , the absorption layer 4 can be made thinner while maintaining the OD value representing the basic performance of the reflective photomask blank and the reflective photomask.

[0067] in addition, Figure 6 This is the result of a simulation of the EUV light reflectivity in the absorption layer region containing indium. Figure 7 Yes Figure 6 The result is obtained by simulating the OD value in .

[0068] As simulation conditions, the photomask structure was set to the following layer structure: below the absorption layer was a capping layer (intermediate layer 2b) made of ruthenium (Ru) with a thickness of 2.5 nm; below the capping layer was a multilayer reflection layer 2a formed by stacking 40 pairs of stacked films with silicon and molybdenum as a pair; below the multilayer reflection layer 2a was a flat substrate 1 made of synthetic quartz; on the back of the substrate 1 was a back conductive layer made of chromium nitride (CrN). Two types of tantalum film and indium oxide film with a tantalum content of 30 atomic % were used as the absorption layer 4. The refractive index of the tantalum film was 0.94 and the attenuation coefficient was 0.041. The refractive index of the indium oxide film with a tantalum content of 30 atomic % was 0.93 and the attenuation coefficient was 0.059.

[0069] Depend on Figure 6 It can be seen that, compared with the case where the tantalum film is used as the absorption layer, when the indium oxide film containing tantalum is used as the absorption layer, for example, when the absorption layer has the same film thickness, the EUV light reflectivity can be greatly reduced. In addition, when the reflectivity is the same, the film thickness can be greatly reduced. Therefore, it is effective to use the indium oxide film containing tantalum as a constituent element of the high absorption layer at the wavelength of EUV light.

[0070] Depend on Figure 7 It can be seen that in order to obtain an OD value of 1 or more, the tantalum film needs to have a film thickness of at least 40 nm, while the tantalum-containing indium oxide film can have a film thickness of less than half, that is, about 18 nm. From this, it can be seen that from the perspective of OD value, it is effective to use the tantalum-containing indium oxide film as a component that can reduce the thickness of the entire absorption layer compared to the tantalum film.

[0071] In addition, in order to obtain an OD value of 2 or more, the tantalum film needs to have a film thickness of at least 70 nm, while the tantalum-containing indium oxide film can have a film thickness of 33 nm. It can be seen that, compared with the tantalum film, even at an OD value of 2 or more, the tantalum-containing indium oxide film is effective as a component that can reduce the thickness of the entire absorption layer.

[0072] Therefore, by using an indium oxide film containing tantalum for the absorption layer, the absorption layer can be made thinner while maintaining the OD value representing the basic performance of the reflective photomask blank and the reflective photomask.

[0073] Figure 8 This is the result of a simulation of the EUV light reflectivity in the absorber layer region containing tellurium. Fig. 9 Yes Figure 8 The result is obtained by simulating the OD value in .

[0074] As a simulation condition, the photomask structure was set to the following layer structure: below the absorption layer was a capping layer (intermediate layer 2b) made of ruthenium (Ru) with a thickness of 2.5 nm; below the capping layer was a multilayer reflection layer 2a formed by stacking 40 pairs of stacked films with silicon and molybdenum as a pair; below the multilayer reflection layer 2a was a flat substrate 1 made of synthetic quartz; on the back of the substrate 1 was a back conductive layer made of chromium nitride (CrN). Two types of tantalum film and tellurium oxide film with a tantalum content of 30 atomic % were used in the absorption layer 4. The refractive index of the tantalum film was 0.94 and the attenuation coefficient was 0.041. The refractive index of the tellurium oxide film with a tantalum content of 30 atomic % was 0.95 and the attenuation coefficient was 0.062.

[0075] Depend on Figure 8 It can be seen that, compared with the case where the tantalum film is used as the absorption layer 4, when the tellurium oxide film containing tantalum is used as the absorption layer, for example, when the absorption layer has the same film thickness, the EUV light reflectivity can be greatly reduced. In addition, when the reflectivity is the same, the film thickness can be greatly reduced. Therefore, it is effective to use the tellurium oxide film containing tantalum as a component of the high absorption layer at the wavelength of EUV light.

[0076] Depend on Fig. 9 It can be seen that in order to obtain an OD value of 1 or more, the tantalum film needs to have a film thickness of at least 40 nm, while the tantalum-containing tellurium oxide film can have a film thickness of less than half, that is, about 18 nm. From this, it can be seen that from the perspective of OD value, the tantalum-containing tellurium oxide film is effective as a component that can reduce the thickness of the entire absorption layer compared to the tantalum film.

[0077] In addition, in order to obtain an OD value of 2 or more, the tantalum film needs to have a film thickness of at least 70 nm, while the tantalum-containing tellurium oxide film can have a film thickness of 33 nm. It can be seen that, compared with the tantalum film, even at an OD value of 2 or more, the tantalum-containing tellurium oxide film is effective as a component that can reduce the thickness of the entire absorption layer.

[0078] Therefore, by using a tellurium oxide film containing tantalum for the absorption layer 4 , the absorption layer 4 can be made thinner while maintaining the OD value representing the basic performance of the reflective photomask blank and the reflective photomask.

[0079] <Durability (radiation resistance)>

[0080] In a conventional EUV exposure apparatus, a photomask is placed in a hydrogen radical atmosphere, and therefore, the photomask needs to have durability (irradiation resistance) against EUV irradiation in a hydrogen radical atmosphere.

[0081] The absorption layer 4 of this embodiment contains a second material (at least one of a transition metal, bismuth, and silicon), which is less reactive and less volatile to hydrogen than other metal materials. As a result, according to this embodiment, exposure damage to the absorption layer 4 by EUV light can be suppressed, thereby achieving sufficient radiation resistance.

[0082] When the absorption layer 4 has a laminated structure, durability (irradiation resistance) against EUV irradiation in a hydrogen radical atmosphere can be obtained by making at least the outermost layer contain the second material.

[0083] Here, transition metals, bismuth, and silicon, which are the second materials, have high reactivity with fluorine and can therefore also be processed by etching.

[0084] The transition metal contained in the absorption layer 4 can be selected from tantalum, gold, osmium, hafnium, tungsten, platinum, iridium, rhenium and zirconium, which have low reactivity with hydrogen. In addition, the transition metal contained in the absorption layer 4 can include one or more of the above metals.

[0085] When the absorption layer 4 has a single-layer structure, the total ratio of the transition metal, bismuth, and silicon contained in the absorption layer 4 is preferably greater than 20 atomic % and less than 50 atomic %.

[0086] When the absorption layer 4 has a laminated structure, the total ratio of the transition metal, bismuth, and silicon contained in at least the outermost layer of the absorption layer 4 is preferably greater than 20 atomic % and less than 50 atomic %.

[0087] In the case where the absorption layer 4 is a tin oxide film, if the total ratio of the transition metal, bismuth, and silicon contained is greater than 20 atomic % and less than 50 atomic %, the refractive index as an optical constant relative to EUV light hardly changes. In addition, the attenuation coefficient can be maintained at 0.050 or more. In addition, by setting it to a content within this range, sufficient radiation resistance to EUV light can also be obtained. Thus, the tin oxide film containing transition metals, bismuth, or silicon can obtain better light absorption than Ta as an existing absorption film forming material, and can obtain sufficient radiation resistance to EUV exposure.

[0088] Similarly, in the case where the absorption layer 4 is an indium oxide film, if the total ratio of the transition metal, bismuth, and silicon contained is greater than 20 atomic % and less than 50 atomic %, the refractive index as an optical constant relative to EUV light hardly changes. In addition, the attenuation coefficient can be maintained at 0.05 or more. In addition, by setting it to a content within this range, sufficient radiation resistance to EUV light can also be obtained. Thus, the indium oxide film containing transition metals, bismuth, or silicon can obtain better light absorption than Ta as an existing absorption film forming material, and can obtain sufficient radiation resistance to EUV exposure.

[0089] In addition, when the absorption layer 4 is a tellurium oxide film, if the total ratio of the transition metal, bismuth, and silicon contained is greater than 20 atomic % and less than 50 atomic %, the refractive index as an optical constant relative to EUV light hardly changes. In addition, the attenuation coefficient can be maintained at 0.05 or more. In addition, by setting it to a content within this range, sufficient radiation resistance to EUV light can also be obtained. Thus, the tellurium oxide film containing transition metals, bismuth, or silicon can obtain better light absorption than Ta, which is a conventional absorption film forming material, and can obtain sufficient radiation resistance to EUV exposure.

[0090] (Reflective layer)

[0091] Figure 1 and Figure 2 The illustrated reflective layer 2 includes a multilayer reflective layer 2a and an intermediate layer 2b formed on the multilayer reflective layer 2a.

[0092] The multilayer reflective layer 2 a is composed of, for example, a plurality of pairs of stacked films in which a silicon (Si) film and a molybdenum (Mo) film are stacked.

[0093] Examples of the intermediate layer 2b include a capping layer, a buffer layer (buffer layer), and an etching stopper layer. The capping layer functions as a protective layer for protecting the multilayer reflective layer 2a. The capping layer is formed of, for example, ruthenium (Ru).

[0094] (Other functions)

[0095] As described above, according to the reflective photomask blank 10 and the reflective photomask 20 of the present embodiment, the radiation resistance during EUV exposure can be improved, and the life of the reflective photomask can be extended.

[0096] Furthermore, according to the present embodiment, by making the absorption film thinner, the EUV light absorption can be improved, so that the influence of the projection effect can be alleviated and the resolution of the pattern transferred onto the wafer can be improved.

[0097] Example

[0098] Hereinafter, embodiments of a reflective photomask blank and a reflective photomask according to the present invention will be described.

[0099] (First embodiment)

[0100] First, an example in which tin (tin oxide film) is contained in the absorption layer will be described.

[0101] [Example 1-1]

[0102] like Fig.10As shown, a multilayer reflective layer (multilayer reflective layer) 12 formed by stacking 40 pairs of laminated films each of silicon (Si) and molybdenum (Mo) is formed on a substrate 11 of synthetic quartz having low thermal expansion characteristics. The film thickness of the multilayer reflective layer 12 is 280 nm.

[0103] Next, a capping layer 13 made of ruthenium (Ru) with a film thickness of 2.5 nm was formed as an intermediate layer on the multilayer reflective layer 12. Thus, a reflective layer 2 having the multilayer reflective layer 12 and the capping layer 13 was formed on the substrate 11. Tantalum and tin oxide were mixed and formed on the capping layer 13 to form an absorption layer 14 having a tin oxide film containing tantalum, thereby manufacturing a reflective photomask blank 100. In addition, as Fig.10 As shown, a back conductive layer 15 made of chromium nitride (CrN) is formed on the back surface of the substrate 11 with a film thickness of 100 nm.

[0104] Here, each layer of film on the substrate 11 can be formed using various sputtering devices. In addition, the absorption layer 14 is set as a tantalum-containing tin oxide film. In the reactive sputtering method, the tantalum content is implemented by adjusting the power applied to each target of tantalum and tin. In addition, the film thickness of each layer is controlled by the sputtering time.

[0105] Next, refer to Figure 11 to Figure 13 A method for producing the reflective photomask 200 will be described.

[0106] like Fig.11 As shown, a positive type chemical amplification resist (SEBP9012: manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to a thickness of 120 nm on the absorption layer 14 of the reflective photomask blank 100 to form a resist film 16 .

[0107] Next, a predetermined pattern was drawn on the positive chemical amplification resist using an electron beam plotter (JBX3030: manufactured by JEOL Ltd.). Then, a PEB treatment was performed on the positive chemical amplification resist at 110°C for 10 minutes, followed by spray development (SFG3000: manufactured by Sigma-Aldrich). Fig.11 As shown, a resist pattern 16a is formed.

[0108] Next, the resist pattern 16a is used as an etching mask, and dry etching is performed mainly using a chlorine-based gas to pattern the absorption layer 14, thereby Fig.12 As shown, an absorption layer pattern is formed on the absorption layer 14. Next, the remaining resist pattern 16a is peeled off, thereby manufacturing the reflective photomask 200 of this embodiment.

[0109] In this embodiment, the absorption layer pattern 14a formed on the absorption layer 14 includes: a line width 64nm LS (Line and Space) pattern on the reflective photomask 200 for transfer evaluation, a line width 200nm LS pattern for absorption layer film thickness measurement using AFM, and a 4mm side absorption layer removal portion for EUV reflectivity measurement.

[0110] In Example 1-1, the atomic ratio of tantalum in the absorption layer 14 composed of tantalum-containing tin oxide was set to three types: 21 atomic %, 30 atomic %, and 49 atomic %. The film thickness of the absorption layer 14 was set to two types: 33 nm and 18 nm. In addition, for tantalum 21 atomic %, a plurality of samples were prepared in which the film thickness of the absorption layer 14 was changed in the range of 16 nm to 45 nm (see Table 1 and Table 3).

[0111] [Example 1-2]

[0112] The absorption layer 14 was made into a tin oxide film containing bismuth, and the target was changed to a combination of tin and bismuth. By the same method as in Example 1, a reflective photomask blank 100 and a reflective photomask 200 were produced.

[0113] In Example 1-2, the atomic ratio of bismuth in the absorption layer 14 composed of bismuth-containing tin oxide was set to two types: 21 atomic % and 40 atomic %. The film thickness of the absorption layer 14 was set to two types: 33 nm and 18 nm (see Table 2).

[0114] [Comparative Example 1-1]

[0115] In Comparative Example 1-1, the absorption layer was made into a tantalum film, and the target was changed to only tantalum, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 1-1 (however, since the target was only tantalum, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 70 nm and 40 nm.

[0116] [Comparative Example 1-2]

[0117] In Comparative Example 1-2, the absorption layer was made into a tin oxide film, and the target was changed to only tin, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 1-1 (however, since the target was only tin, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 26 nm and 17 nm.

[0118] [Comparative Examples 1-3]

[0119] In Comparative Example 1-3, as in Example 1-1, the absorption layer was made into a tantalum-containing tin oxide film, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 1-1. The atomic ratio of tantalum in the absorption layer composed of tantalum-containing tin oxide was set to 70 atomic %, and the film thickness of the absorption layer was set to two types: 40 nm and 24 nm.

[0120] In the above-mentioned Examples and Comparative Examples, the film thickness was measured by a transmission electron microscope, and the atomic ratio in the absorption layer was measured by XPS (X-ray photoelectron spectroscopy), and was confirmed respectively.

[0121] The reflectivity Rm of the reflective layer region and the reflectivity Ra of the absorption layer region of the reflective photomask produced in each of the above-mentioned embodiments and comparative examples were measured using an EUV light reflectivity measuring device. The reflectivity Rm was measured in the absorption layer removal portion with a side length of 4 mm. Based on the measurement results, the OD value was calculated using formula (1).

[0122] (Wafer exposure evaluation)

[0123] The absorption layer pattern of the reflective photomask prepared in the examples and comparative examples was transferred and exposed on a semiconductor wafer (not shown) coated with a positive chemical amplification resist for EUV using an EUV exposure device (NXE3300B: manufactured by ASML). The transferred resist pattern was observed using an electron beam sizer, and line width measurement was performed to confirm the resolution.

[0124] (Radiation resistance)

[0125] The radiation resistance of the reflective photomask during EUV exposure was evaluated using an EUV exposure apparatus NXE3300B (manufactured by ASML). At this time, the reflective photomasks prepared in the examples and comparative examples were irradiated with 30 kJ / cm 2 The atmosphere during exposure was a vacuum atmosphere of 3 Pa with hydrogen introduced. The thickness change of the absorption layer before and after EUV light irradiation was confirmed using an atomic force microscope (AFM). The measurement was performed on a LS pattern with a line width of 200 nm.

[0126] In addition, when the film thickness change of the absorption layer was 1.0 nm or less, it was determined that there was no damage.

[0127] The evaluation results are shown in Tables 1 to 3.

[0128] [Table 1]

[0129]

[0130] [Table 2]

[0131]

[0132] [Table 3]

[0133]

[0134] Table 1 shows the cases where a tantalum film, a tin oxide film, and a tantalum-containing tin oxide film are used in the absorption layer, and the OD values ​​are all close to 1.0 and 2.0. Except for the tin oxide film (Comparative Example 1-2), the absorption layer has good results in EUV radiation resistance under a hydrogen atmosphere. Except for the case where the absorption layer is a tantalum film (Comparative Example 1-1), the resolution is less than 20nm, and the results are good. By setting the absorption layer to a tantalum-containing tin oxide film, good radiation resistance and good resolution can be achieved (Example 1-1, Comparative Example 1-3).

[0135] It is also known that, as shown in Example 1-1, by setting the tantalum content of the tantalum-containing tin oxide film to be greater than 20 atomic % and less than 50 atomic %, the resolution is reduced to 15 nm or less, resulting in better results.

[0136] Table 2 shows the case where a bismuth-containing tin oxide film is used in the absorption layer (Example 1-2). In Example 1-2, the absorption layer has an EUV radiation resistance of 1.0 nm or less and a resolution of 15 nm or less in a hydrogen atmosphere. Therefore, according to this example, both radiation resistance and resolution are good results.

[0137] Table 3 shows the case where a tantalum-containing tin oxide film having a tantalum content of 21 atomic % is used in the absorption layer. Then, the film thickness of the absorption layer is changed within a range of 16 nm to 45 nm for evaluation. The absorption layer has good results in terms of EUV resistance of 1.0 nm or less and resolution of 20 nm or less in a hydrogen atmosphere. In addition, as can be seen from Table 3, by setting the film thickness of the absorption layer to 18 nm or more and 45 nm or less, the resolution becomes 17 nm or less, and better results are obtained. In addition, by setting the film thickness of the absorption layer to 18 nm or more and 35 nm or less, the resolution becomes 15 nm or less, and further good results are obtained.

[0138] (Second embodiment)

[0139] Next, an example in which the absorption layer contains indium (indium oxide film) will be described.

[0140] [Example 2-1]

[0141] like Fig.10 As shown, a multilayer reflective layer 12 formed by laminating 40 pairs of laminated films each consisting of silicon (Si) and molybdenum (Mo) is formed on a substrate 11 of synthetic quartz having low thermal expansion characteristics. The film thickness of the multilayer reflective layer 12 is 280 nm.

[0142] Next, a capping layer 13 made of ruthenium (Ru) with a film thickness of 2.5 nm was formed as an intermediate layer on the multilayer reflective layer 12. Thus, a reflective layer 2 having the multilayer reflective layer 12 and the capping layer 13 was formed on the substrate 11. Tantalum and indium oxide were mixed and formed on the capping layer 13 to form an absorption layer 14 having an indium oxide film containing tantalum, thereby manufacturing a reflective photomask blank 100. In addition, as Fig.10 As shown, a back conductive layer 15 made of chromium nitride (CrN) is formed on the back surface of the substrate 11 with a film thickness of 100 nm.

[0143] Each layer of film on the substrate 11 can be formed using various sputtering devices. The absorption layer 14 is set as an indium oxide film containing tantalum. In the reactive sputtering method, the tantalum content is implemented by adjusting the power applied to each target of tantalum and indium. In addition, the film thickness of each layer is controlled by the sputtering time.

[0144] The reflective photomask 200 was produced by the same method as in the first embodiment.

[0145] In Example 2-1, the atomic ratio of tantalum in the absorption layer 14 composed of tantalum-containing indium oxide was set to three types: 21 atomic %, 30 atomic %, and 49 atomic %. The film thickness of the absorption layer 14 was set to two types: 33 nm and 18 nm. In addition, for tantalum 21 atomic %, the film thickness of the absorption layer 14 was changed within the range of 16 nm to 45 nm.

[0146] [Example 2-2]

[0147] The absorption layer 14 was made into an indium oxide film containing tungsten, and the target was changed to a combination of indium and tungsten. By the same method as in Example 1, a reflective photomask blank 100 and a reflective photomask 200 were produced.

[0148] In Example 2-2, the atomic ratio of tungsten in the absorption layer 14 composed of tungsten-containing indium oxide was set to two types: 21 atomic % and 40 atomic %. The film thickness of the absorption layer 14 was set to two types: 34 nm and 18 nm.

[0149] [Comparative Example 2-1]

[0150] The absorption layer was made into a tantalum film, and the target was changed to only tantalum, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 2-1 (however, since the target was only tantalum, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 70nm and 40nm.

[0151] [Comparative Example 2-2]

[0152] The absorption layer was made into an indium oxide film, and the target was changed to only indium, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 2-1 (however, since the target only contained indium, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 27 nm and 18 nm.

[0153] [Comparative Example 2-3]

[0154] As in Example 2-1, the absorption layer was made of an indium oxide film containing tantalum, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 2-1. The atomic ratio of tantalum in the absorption layer composed of indium oxide containing tantalum was set to 70 atomic %, and the film thickness of the absorption layer was set to two types: 40 nm and 24 nm.

[0155] The evaluation was performed by the same evaluation method as in the first embodiment.

[0156] These evaluation results are shown in Tables 4 to 6.

[0157] [Table 4]

[0158]

[0159] [Table 5]

[0160]

[0161] [Table 6]

[0162]

[0163] Table 4 shows the cases where tantalum film, indium oxide film and indium oxide film containing tantalum are used in the absorption layer, and the OD values ​​are close to 1.0 and 2.0. Except for the indium oxide film (Comparative Example 2-2), the EUV radiation resistance of the absorption layer in a hydrogen atmosphere obtained good results. Except for the case where the absorption layer is a tantalum film (Comparative Example 2-1), the resolution is less than 20nm, and the result is good. In addition, it can be seen that by setting the absorption layer to an indium oxide film containing tantalum, good radiation resistance and good resolution can be achieved (Example 2-1, Comparative Example 2-3). In addition, it can be seen that as shown in Example 2-1, by making the tantalum content of the indium oxide film containing tantalum greater than 20 atomic % and less than 50 atomic %, the resolution becomes less than 15nm, and the result is better.

[0164] Table 5 shows the case where an indium oxide film containing tungsten is used in the absorption layer (Example 2-2). In Example 2-2, the absorption layer has an EUV radiation resistance of 1.0 nm or less and a resolution of 15 nm or less in a hydrogen atmosphere. Good results were obtained for both radiation resistance and resolution.

[0165] Table 6 shows the case where a tantalum-containing indium oxide film having a tantalum content of 21 atomic % is used in the absorption layer. The evaluation was performed by varying the film thickness of the absorption layer between 16 nm and 45 nm. According to Example 2-1, the EUV irradiation resistance of the absorption layer in a hydrogen atmosphere was 1.0 nm or less, and the resolution was 20 nm or less, both of which were good results. By setting the film thickness of the absorption layer to 18 nm or more and 45 nm or less, the resolution was 17 nm or less, and better results were obtained. In addition, by setting the film thickness of the absorption layer to 18 nm or more and 35 nm or less, the resolution was 15 nm or less, and further good results were obtained.

[0166] (Third embodiment)

[0167] Next, an example in which tellurium is contained in the absorption layer (tellurium oxide film) will be described.

[0168] [Example 3-1]

[0169] like Fig.10 As shown, a multilayer reflective layer 12 formed by laminating 40 pairs of laminated films each consisting of silicon (Si) and molybdenum (Mo) is formed on a substrate 11 of synthetic quartz having low thermal expansion characteristics. The film thickness of the multilayer reflective layer 12 is 280 nm.

[0170] Next, a capping layer 13 made of ruthenium (Ru) with a film thickness of 2.5 nm was formed as an intermediate layer on the multilayer reflective layer 12. Thus, a reflective layer 2 having the multilayer reflective layer 12 and the capping layer 13 was formed on the substrate 11. Tantalum and tellurium oxide were mixed and formed on the capping layer 13 to form an absorption layer 14 having a tellurium oxide film containing tantalum, thereby manufacturing a reflective photomask blank 100. In addition, as Fig.10 As shown, a back conductive layer 15 made of chromium nitride (CrN) is formed on the back surface of the substrate 11 with a film thickness of 100 nm.

[0171] Each layer of film on the substrate 11 can be formed using various sputtering devices. In addition, the absorption layer 14 is set as a tellurium oxide film containing tantalum. In the reactive sputtering method, the tantalum content is implemented by adjusting the power applied to each target of tantalum and tellurium. In addition, the film thickness of each layer is controlled by the sputtering time.

[0172] The reflective photomask 200 was produced by the same method as in the first embodiment.

[0173] In Example 3-1, the atomic ratio of tantalum in the absorption layer 14 composed of tellurium oxide containing tantalum was set to three types: 21 atomic %, 30 atomic %, and 49 atomic %. The film thickness of the absorption layer 14 was set to two types: 33 nm and 18 nm. In addition, for 21 atomic % of tantalum, the film thickness of the absorption layer 14 was changed within the range of 16 nm to 45 nm.

[0174] [Example 3-2]

[0175] The absorption layer 14 was made into a tellurium oxide film containing hafnium, and the target was changed to a combination of tellurium and hafnium. By the same method as in Example 1, a reflective photomask blank 100 and a reflective photomask 200 were produced.

[0176] In Example 3-2, the atomic ratio of hafnium in the absorption layer 14 composed of hafnium-containing tellurium oxide was set to two types: 21 atomic % and 40 atomic %. The film thickness of the absorption layer 14 was set to two types: 33 nm and 18 nm.

[0177] [Comparative Example 3-1]

[0178] In Comparative Example 3-1, the absorption layer was made into a tantalum film, and the target was changed to only tantalum, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 3-1 (however, since the target was only tantalum, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 70 nm and 40 nm.

[0179] [Comparative Example 3-2]

[0180] In Comparative Example 3-2, the absorption layer was made into a tellurium oxide film, and the target was changed to tellurium only, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 3-1 (however, since the target was tellurium only, the content was not adjusted by adjusting the applied power). The film thickness of the absorption layer was set to two types: 31 nm and 17 nm.

[0181] [Comparative Example 3-3]

[0182] In Comparative Example 3-3, as in Example 3-1, the absorption layer was made into a tellurium oxide film containing tantalum, and a reflective photomask blank and a reflective photomask were produced by the same method as in Example 3-1. The atomic ratio of tantalum in the absorption layer composed of tellurium oxide containing tantalum was set to 70 atomic %, and the film thickness of the absorption layer was set to two types: 40 nm and 24 nm.

[0183] The evaluation was performed by the same method as in the first embodiment.

[0184] These evaluation results are shown in Tables 7 to 9.

[0185] [Table 7]

[0186]

[0187] [Table 8]

[0188]

[0189] [Table 9]

[0190]

[0191] Table 7 shows the cases where tantalum film, tellurium oxide film and tellurium oxide film containing tantalum are used in the absorption layer, and the OD values ​​are close to 1.0 and 2.0. Except for the tellurium oxide film (Comparative Example 3-2), the EUV radiation resistance of the absorption layer in a hydrogen atmosphere obtained good results. Except for the case where the absorption layer is a tantalum film (Comparative Example 3-1), the resolution is less than 20nm, and the result is good. By setting the absorption layer to a tellurium oxide film containing tantalum, good radiation resistance and good resolution can be achieved. As shown in Example 3-1, it can be seen that by making the tantalum content of the tellurium oxide film containing tantalum greater than 20 atomic % and less than 50 atomic %, the resolution becomes less than 15nm, and the result is better.

[0192] Table 8 shows the case where a tellurium oxide film containing hafnium is used in the absorption layer (Example 3-2). The absorption layer has an EUV radiation resistance of 1.0 nm or less and a resolution of 15 nm or less in a hydrogen atmosphere. In Example 3-2, both radiation resistance and resolution are good.

[0193] Table 9 shows the case where a tantalum-containing tellurium oxide film having a tantalum content of 21 atomic % is used in the absorption layer. The evaluation was performed by varying the film thickness of the absorption layer within a range of 16 nm to 45 nm. Good results were obtained for the EUV irradiation resistance of the absorption layer in a hydrogen atmosphere of 1.0 nm or less and the resolution of 20 nm or less. Better results were obtained by setting the film thickness of the absorption layer to 18 nm or more and 45 nm or less, and the resolution was 17 nm or less. In addition, by setting the film thickness of the absorption layer to 18 nm or more and 35 nm or less, the resolution was 15 nm or less, and further good results were obtained.

[0194] Explanation of symbols

[0195] 10, 100 Reflective photomask blanks

[0196] 20, 200 reflective photomask

[0197] 1 substrate

[0198] 2 Reflection layer

[0199] 2a Multi-layer reflective layer

[0200] 2b Middle layer

[0201] 4 Absorption layer

[0202] 4a Absorption layer pattern

[0203] 11 base plate

[0204] 12. Multi-layer reflective layer

[0205] 13 Capping layer

[0206] 14 Absorption layer

[0207] 14a Absorption layer pattern

[0208] 15 Back conductive layer

[0209] 16 Resist film

[0210] 16a Resist pattern

Claims

1. A reflective photomask blank, characterized in that: A reflection layer for reflecting incident light and an absorption layer for absorbing incident light are sequentially formed on one surface of the substrate. The absorption layer includes one or more layers, wherein at least the outermost layer of the layers contains: a first material selected from the group consisting of tin, indium, and tellurium, and a second material consisting of one or more materials selected from the group consisting of transition metals, bismuth, and silicon. The content of the second material in the same layer is greater than 20 atomic % and less than 50 atomic %.

2. The reflective photomask blank according to claim 1, wherein: The absorption layer further contains oxygen at least in the outermost layer. The ratio of the number of atoms of the second material to the total number of atoms of the first material and oxygen is within a range of greater than 1 / 4 and less than 1.

3. The reflective photomask blank according to claim 1 or claim 2, characterized in that: The transition metal is one or more selected from the group consisting of tantalum, gold, osmium, hafnium, tungsten, platinum, iridium, rhenium, and zirconium.

4. The reflective photomask blank according to claim 1 or claim 2, characterized in that: When the intensity of the reflected light from the reflective layer is Rm and the intensity of the reflected light from the absorption layer is Ra, and the optical density OD of the reflective layer and the absorption layer is defined by the following formula (1), OD = -log(Ra / Rm) ··· (1) The value of the optical density OD is 1 or more.

5. The reflective photomask blank according to claim 1 or claim 2, characterized in that: The absorption layer has a thickness of 18 nm or more and less than 45 nm.

6. The reflective photomask blank according to claim 1 or claim 2, characterized in that: The reflective layer includes: a multilayer reflective layer composed of a multilayer structure, and an intermediate layer formed on the multilayer reflective layer.

7. A reflective photomask, characterized in that: have: a reflective layer formed on one surface of the substrate and reflecting incident light, and an absorption layer formed in a predetermined pattern on the reflective layer and absorbing the incident light, The absorption layer includes one or more layers, wherein at least the outermost layer of the layers contains: a first material selected from the group consisting of tin, indium, and tellurium, and a second material consisting of one or more materials selected from the group consisting of transition metals, bismuth, and silicon. The content of the second material in the same layer is greater than 20 atomic % and less than 50 atomic %.

Images