Reflective mask blank and method for manufacturing a reflective mask

Abstract

To provide a reflection type mask blank small in reduction of a degree of reflection, and maintaining a high degree of reflection even when heat treatment is performed, and a production method of a reflection type mask using the reflection type mask blank.SOLUTION: A reflection type mask blank includes: a substrate 10; a multilayered reflection coating 20 for reflecting exposure light and provided on the substrate 10; a protective coating 50 including a metal oxide coating 51 provided on the multilayered reflection coating 20; and an absorber coating 70 for absorbing exposure light and provided on the protective coating 50. The multilayered reflection coating 20 is obtained by alternately laminating Mo layers 22 and Si layers 21 where a layer of a side most separated from the substrate 10 is the Si layer 21. In the metal oxide coating 50, an oxygen content of a layer of a side separated from the substrate 10 is high in comparison with a substrate 10 side.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a reflective mask for manufacturing a reflective mask used in the manufacture of semiconductor devices, etc. The present invention relates to a method for manufacturing a mask blank and a reflective mask. [Background technology]

[0002] In the manufacturing process of semiconductor devices (semiconductor equipment), exposure light is irradiated onto a transfer mask, and the mask The circuit pattern formed on the semiconductor substrate (semiconductor wafer) is projected onto the semiconductor substrate through a reduced projection optical system. ) is repeatedly transferred onto the photolithography technology. Conventionally, the wavelength of the exposure light is The mainstream is 193 nm using argon fluoride (ArF) excimer laser light, We use a process called multi-patterning, which combines multiple optical processes and processing processes. By using this method, patterns with dimensions smaller than the exposure wavelength have finally been formed.

[0003] However, with the continued miniaturization of device patterns, the formation of even finer patterns is required. Therefore, the wavelength of the exposure light is shorter than that of the ArF excimer laser light. Extreme ultraviolet (hereinafter referred to as "EUV") light is used. EUV lithography technology, which was previously used for lithography, is now being used. EUV light has a wavelength of 0. It is light with a wavelength of about 2 to 100 nm, more specifically, light with a wavelength of about 13.5 nm. This EUV light has extremely low transmittance through materials, so conventional transmission type projection optics and masks cannot be used. Therefore, a reflective optical element is used. Reflective masks have also been proposed.

[0004] Reflective masks have a multilayer reflective film formed on the substrate that reflects EUV light. On the other hand, the absorber film is patterned to absorb EUV light. The state before patterning (including the state where a resist film is formed) is a reflective mask. This is called a scribing blank, and is used as a material for reflective masks (hereafter referred to as EUV light). A reflective mask blank is also called an EUV mask blank. The rank is determined by the multilayer reflective film formed on the glass substrate that reflects EUV light and the The multilayer reflective layer has a basic structure including an absorber film that absorbs the EUV light. The layer is usually made by alternately stacking molybdenum (Mo) and silicon (Si) layers. A Mo / Si multilayer reflective film is used to ensure the reflectivity of EUV light. is a material whose main component is tantalum (Ta), which has a relatively large extinction coefficient for EUV light. is used.

[0005] A protective film for protecting the multilayer reflective film is formed between the multilayer reflective film and the absorber film. This protective film is etched and patterned to form a pattern on the absorber film. Pattern correction processing when defects are detected after turn formation, as well as mask pattern formation To prevent the multilayer reflective coating from being damaged later when cleaning the mask, etc. The purpose of this protective film is to protect the protective film. As disclosed in Patent Publication No. 2981 (Patent Document 1), ruthenium (Ru) is used. do. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-122981 Summary of the Invention [Problem to be solved by the invention]

[0007] The reflective mask blank is a multilayer mask made by alternately stacking Mo and Si layers, with the top layer being Si. A protective film mainly composed of Ru is formed on the reflective film (multi-layer periodic film), stabilizing subsequent processes. To achieve this, heat treatment is generally carried out at a temperature range of 120 to 200°C.

[0008] However, the combination of a protective film containing Ru and a multilayer reflective film with a Si surface layer is difficult to achieve by heat treatment. The RuSi diffusion layer is formed by the process, and the reflectance tends to decrease significantly. The interface of the Si film is protected by a buffer between the Ru film and the Si film to prevent the formation of a diffusion layer due to heat treatment. A structure in which a Mo film or the like is formed as the protective layer is also being considered, but the protective film is thin and cannot absorb oxygen. When the buffer layer itself is easily oxidized, the reflectance is significantly reduced. If the protective film is made of a metal oxide film with a high oxygen content, the reflectance due to heat treatment can be reduced. While this can keep fluctuations to a minimum, it can also increase the surface layer of the multilayer reflective film by increasing the amount of acid that is required during lamination. This may cause the surface to deteriorate, resulting in a significant decrease in reflectivity.

[0009] The present invention has been made in view of the above points, and is intended to provide a method for preventing reflection even when heat treatment is performed. Reflective mask blank with little decrease in reflectance and maintaining high reflectance, and The present invention provides a method for manufacturing a reflective mask using a mask. [Means for solving the problem]

[0010] The reflective mask blank according to the present invention comprises: A substrate; a multilayer reflective film provided on the substrate and reflecting exposure light; a protective film including a metal oxide film provided on the multilayer reflective film; an absorber film provided on the protective film to absorb exposure light; Equipped with The multilayer reflective film is formed by alternately stacking Mo layers and Si layers, and has a side farthest from the substrate. The layer is a Si layer, In the metal oxide film, the oxygen content of the layer on the side away from the substrate is higher than that on the side of the substrate. The amount may be higher.

[0011] In the reflective mask blank according to the present invention, The metal contained in the metal oxide film has an extinction coefficient of 13.53 nm for EUV light. It may be made of a metal with k less than 0.02.

[0012] In the reflective mask blank according to the present invention, The protective film may function as an etching stopper when processing the absorber film.

[0013] In the reflective mask blank according to the present invention, The metal oxide film may contain one or more of Zr, Nb, Ti and Y.

[0014] In the reflective mask blank according to the present invention, The oxygen content of the layer of the metal oxide film on the side away from the substrate is controlled by heat treatment at 120°C to 200°C. It does not have to change logically.

[0015] In the reflective mask blank according to the present invention, The thickness of the metal oxide film may be 0.5 nm or more and less than 3.5 nm.

[0016] In the reflective mask blank according to the present invention, the metal oxide film has a multilayer structure, In comparison with the first layer located on the substrate side, The oxygen content may be high.

[0017] In the reflective mask blank according to the present invention, The oxygen content of the metal oxide film may increase continuously with increasing distance from the substrate. stomach.

[0018] In the reflective mask blank according to the present invention, The Si layer of the multilayer reflective film that is farthest from the substrate has a metal oxide film side that is not oxygen-rich. Other light elements may also be included.

[0019] In the reflective mask blank according to the present invention, a front surface between the Si layer of the multilayer reflective film that is farthest from the substrate and the metal oxide film; an oxidation prevention layer containing a light element other than oxygen on the metal oxide film side; The oxidation prevention layer may have a thickness of 0.2 nm or more and 3 nm or less.

[0020] In the reflective mask blank according to the present invention, The light element may be one or more of nitrogen, carbon, and boron.

[0021] In the reflective mask blank according to the present invention, For EUV light with a wavelength of 13.53 nm before heat treatment at 120 to 200°C EU with first reflectance and wavelength of 13.53 nm after heat treatment at 120-200°C When comparing the second reflectance to V light, the change in the second reflectance relative to the first reflectance is 0. It may be 5% or less.

[0022] In the method for manufacturing a reflective mask according to the present invention, A reflective mask may be manufactured using the above-described reflective mask blank. [Effects of the Invention]

[0023] According to one aspect of the present invention, even when heat treatment is performed, the decrease in reflectance is small and high reflectance can be maintained. Therefore, a reflective mask blank that maintains the original shape can be realized. [Brief explanation of the drawings]

[0024] [Figure 1A] 1 is a cross-sectional view showing an example of a reflective mask blank according to an embodiment of the present invention. [Figure 1B] FIG. 10 is a cross-sectional view showing another example of a reflective mask blank according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view illustrating an example of a reflective mask blank having a SiN-containing layer according to an embodiment of the present invention. [Figure 3A] 1 is a cross-sectional view showing an example of a protective film having a multilayer structure used in an embodiment of the present invention. [Figure 3B] FIG. 10 is a cross-sectional view showing another example of a protective film having a multilayer structure used in an embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view showing the oxygen content in an example of a protective film used in an embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing the oxygen content in another example of a protective film used in an embodiment of the present invention. [Figure 6] FIG. 1 is a cross-sectional view showing an example of a reflective mask blank having an oxidation prevention layer, a hard mask film, a reflectance reduction layer, and a conductive film according to an embodiment of the present invention. [Figure 7] 1 is a cross-sectional view showing an example of a reflective mask blank having an oxidation prevention layer, a buffer layer, a hard mask film, and a conductive film according to an embodiment of the present invention. [Figure 8] FIG. 1 is a cross-sectional view showing an example of a reflective mask blank having a resist film according to an embodiment of the present invention. [Figure 9] 1 is a cross-sectional view showing an example of a reflective mask according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described below.

[0026] As shown in FIGS. 1A and 1B, the EUV mask blank according to this embodiment is made of glass. and a substrate 10 formed on one of the main surfaces of the substrate 10 (on the front surface in this embodiment). The multilayer reflective film 20 reflects the exposure light, specifically, the multilayer reflective film 20 reflects the EUV light. The multilayer reflective film 20 may be provided in contact with one main surface of the substrate 10. The wavelength of EUV light used in EUV lithography as exposure light is 13 to 14 nm, Usually, the wavelength is about 13.5 nm (for example, 13.4 to 13.6 nm).

[0027] The substrate 10 preferably has low thermal expansion characteristics for use in EUV light exposure. For example, the thermal expansion coefficient is ±2×10 -8 / ℃, preferably ±5×10 -9 / ℃ range It is preferable that the substrate 10 is made of a material having a sufficiently flat surface. The surface roughness of the main surface of the substrate 10 is preferably 0.5n in terms of RMS value. The surface roughness of the substrate 10 is preferably 0.2 nm or less, and more preferably 0.2 nm or less. This can be achieved by polishing or the like.

[0028] The multilayer reflective film 20 is a multilayer film in which low refractive index materials and high refractive index materials are alternately stacked, The multilayer reflective film 20 is a film that reflects EUV light, which is exposure light. The silicon layer 21 and the molybdenum layer 22 are alternately stacked. The Si / Mo laminated portion 25 has a structure that is resistant to EUV light. The Si layer (Si layer 21) is a material having a relatively high refractive index relative to EUV light. Mo layers (Mo layers 22), which are materials having a relatively low refractive index, are periodically laminated. Here, the Si layer 21 and the Mo layer 22 are made of elemental silicon and molybdenum, respectively. It may be a layer formed solely of other components or may contain less than 10 percent of other components. The number of stacked Si layers 21 and Mo layers 22 may be, for example, 40 periods or more (40 or more layers for each). ) and preferably 60 periods or less (60 layers or less for each) The thicknesses of the Si layer 21 and the Mo layer 22 of the Si / Mo laminated portion 25 are appropriately set according to the exposure wavelength. The thickness of the Si layer 21 is preferably 5 nm or less, and the thickness of the Mo layer 22 is 4 nm or less. The thickness of the Si layer 21 is preferably 1000 nm or less. The lower limit of the thickness of the Mo layer 22 is not particularly limited, but is usually 1 nm or more. The thickness of the Si layer 21 and the Mo layer 22 is usually 1 nm or more. The thickness of each of the Si layer 21 and the Mo layer 22 may be set to obtain the desired reflectance. The thickness may be constant or may vary among the individual layers. The total thickness is usually about 250 to 450 nm.

[0029] The inventors of the present application have investigated the oxygen content of the protective film 50 on the side away from the multilayer reflective film 20. By increasing the amount of silicon dioxide, oxidation of the film is prevented, and further, the layer in contact with the surface Si layer of the multilayer reflective film 20 is oxidized. By reducing the content of oxygen, it is possible to prevent the multilayer reflective film 20 from being oxidized by heat. Even if a heat treatment at 120 to 200° C. is performed after the formation of the multilayer reflective film 20, the reflective film We have found that it is possible to create a reflective mask blank that maintains high reflectivity with little decrease in reflectivity, The present invention has been achieved. In addition, the protective film 50 is made of Zr, Nb, Ti, Y, etc., which is resistant to EUV light (13. It is particularly preferable that the metal oxide film 51 has an extinction coefficient k of 0.02 or less at wavelengths of 53 nm. It was also confirmed that.

[0030] In this embodiment, the Si / Mo stacked portion 25 is formed between the Si layer 21 and the Mo layer 22. At least one layer containing Si and N is formed in contact with both the Si layer 21 and the Mo layer 22. The layer containing Si and N preferably does not contain oxygen. Specifically, the layer containing SiN (wherein the constituent elements of SiN are Si and N) is The SiN-containing layer 26 is preferred (see FIG. 2). The N content of the layer containing Si and N is preferably 1 atomic % or more, particularly 5 atomic % or more. It is preferable that the Si content is 60 atomic % or less, and particularly 57 atomic % or less. The thickness of the layer containing N is preferably 2 nm or less, and more preferably 1 nm or less. The lower limit of the thickness of the layer containing Si and N is not particularly limited, but is preferably 0. It is preferable that it be 0.1 nm or more.

[0031] In this embodiment, the layer of the multilayer reflective film 20 that is farthest from the substrate 10 is the Si layer 21. The protective film 50 provided on the Si layer 21 is resistant to EUV light (13.53 nm). The protective film may be a metal oxide film 51 made of a metal having an extinction coefficient k of less than 0.02. By using a metal with a coefficient k of less than 0.02, the reduction in reflectance due to the formation of a protective film is suppressed. The protective film 50 may contain a film other than the metal oxide film 51 (for example, a metal film or a resin film). The oxygen content in the metal oxide film 51 may be different. 1, the oxygen content of the layer on the side away from the substrate 10 is higher than that on the substrate 10 side. The metal oxide film 51 may contain one or more elements selected from Zr, Nb, Ti, and Y. By adopting such an embodiment, high reflectance can be obtained, and the side away from the substrate 10 The etching rate during etching of the absorber film 70 can be further reduced. Therefore, the protective film 50 functions as an etching stopper when the absorber film 70 is processed.

[0032] The layer of the metal oxide film 51 on the side farther from the substrate 10 (typically, the S The oxygen content of the outermost Si layer 21a) which is the i-layer 21 is reduced by heat treatment at 120°C to 200°C. Even if oxygen is added, a stable layer with no change in oxygen content, especially an oxygen saturated state, is desirable. Even if heat treatment is applied at temperatures between 120 and 200°C, the oxygen content remains unchanged. This means that the temperature is different between before the heat treatment from 120℃ to 200℃ (first state) and after the heat treatment from 120℃ to 200℃. When compared with the second state after heat treatment at 00°C, the oxygen content in the second state This means that the oxygen content is 95 atomic % or more of the oxygen content in the first state. When an oxygen-unsaturated layer is provided near the interface with the multilayer reflective film 20, This makes it possible to create a film that maintains high reflectivity while minimizing fluctuations in reflectivity. The thickness of the film is 0.5 nm or more, particularly 1 nm or more, and less than 3.5 nm, particularly 3 nm or less, and is preferably 2 nm or less.

[0033] As shown in FIGS. 3A and 3B, the protective film 50 may have a multi-layer structure, and may include a plurality of metal oxides. The metal oxide layer 55 may be formed by laminating a metal oxide layer located on the substrate 10 side. 55, the oxygen content in the other metal oxide layer 55 located on the side remote from the substrate 10. For example, the oxygen content in the metal oxide layer 55 located on the substrate 10 side may be increased. is equal to or less than the oxygen content in the metal oxide layer 55 located on the side away from the substrate 10. As an example, a metal oxide layer (first metal oxide) located on at least one substrate 10 side is In comparison with the metal oxide layer 55, another metal oxide layer (second metal oxide layer) is located on the side away from the substrate 10. The oxygen content in layer 55 is high.

[0034] The oxygen content of the protective film 50 may also increase continuously with increasing distance from the substrate 10. Also, the oxygen content in the metal oxide layer 55 gradually increases from the substrate 10 to the surface of the metal oxide layer 55 (see FIG. 4). It is also possible to make it so that the value increases as the distance increases from the metal oxide layer 55 (see FIG. 5). As an example of an embodiment in which the oxygen content increases stepwise with increasing distance from the substrate 10, 3A, the protective film 50 may have a multi-layer structure. The concentration may be increased in units of atomic percent to 10 atomic percent. Only two layers of the film 50 are provided, and the film 50 is spaced apart from the plate 10 compared to the protective film 50 located on the substrate 10 side. The oxygen content of the protective film 50 located on the side facing the substrate may be made higher. The difference in oxygen content may be about 15 atomic % to 50 atomic %. The oxygen content of the protective film 50 on the side of the substrate 10 is A, and the oxygen content of the protective film 50 on the side farthest from the substrate 10 is A. If the oxygen content of 50 is B, then A×1.15≦B≦A×1.5 may be satisfied.

[0035] In addition, the Si layer 21 (the farthest Si layer) of the multilayer reflective film 20 from the substrate 10 21a) may contain a light element other than oxygen on the metal oxide layer 55 side. 10, the Si layer 21 (the farthest Si layer 21a) on the side farthest from the substrate 10 and the protective film 50 An oxidation prevention layer 60 containing a light element other than oxygen may be provided between the metal oxide layer 55 and the oxide layer 56. (See Figure 6.) Light elements include nitrogen, carbon, boron, etc., and may be any light element other than oxygen. By adopting such an embodiment, when forming the protective film 50 made of the metal oxide film 51 or the like, This reduces the oxidation of the surface Si, making it possible to maintain a high reflectivity. The thickness of the suppression layer 60 is preferably 0.2 nm or more and 3 nm or less. The light element in this state means an element having a weight equal to or less than that of oxygen. Between the insulating film 1a and the protective film 50, an oxidation suppression layer 60 and a buffer layer 140 such as a SiN-containing layer 26 are formed. Both may be provided (see Figures 2 and 7).

[0036] The laminate of the multilayer reflective film 20 and the protective film 50 on the substrate 10 is heated at 120 to 200°C. The primary reflectance to EUV light (13.53 nm) before treatment and the temperature at 120 to 200°C When comparing the second reflectance to EUV light (13.53 nm) after heat treatment, The change in the second reflectance relative to the first reflectance may be 0.5% or less.

[0037] A reflective mask as shown in FIG. 9 is manufactured using the reflective mask blank of this embodiment. This embodiment also provides a method for manufacturing a reflective mask.

[0038] The Si / Mo laminated portion 25 is formed by supplying power to a target and then heating the supplied power. The sputtering method involves turning atmospheric gas into plasma (ionization) and performing sputtering. One example of the sputtering method is the ion beam sputtering method, in which an ion beam is irradiated onto a target. DC sputtering is used to apply a direct current voltage to the target, while high frequency voltage is used to apply a high frequency voltage to the target. The sputtering method involves introducing sputtering gas into a chamber. A voltage is applied to the target, the gas is ionized, and the sputtering phenomenon caused by the gas ions occurs. The film formation method used, particularly the magnetron sputtering method, is advantageous in terms of productivity. The power applied to the target can be DC or RF. DC has the advantage of being able to charge the target. To prevent sputtering, the negative bias applied to the target is reversed for a short period of time. This also includes ng.

[0039] The Si / Mo laminated portion 25 is formed by using, for example, a sputtering device capable of mounting a plurality of targets. Specifically, the silicon layer 21 can be formed by sputtering. a silicon (Si) target and a molybdenum (Mo) target for forming the Mo layer 22 When the Si layer 21 and the Mo layer 22 are formed, helium is used as the sputtering gas. (He) gas, argon (Ar) gas, krypton (Kr) gas, xenon (Xe) gas The Si target and the Mo target are sequentially sputtered using a rare gas such as In this way, the Si layer 21 and the Mo layer 22 can be formed in sequence.

[0040] The metal oxide layer 55 may be formed by, for example, ion beam sputtering or magnetic deposition, similar to the multilayer reflective film 20. The protective film 50 can be formed by magnetron sputtering. The sputtering gases used were helium (He), argon (Ar), and crypto Kr gas, xenon (Xe) gas, and other rare gases, and, if necessary, oxygen-containing gas, nitrogen It is formed by sputtering using reactive gases such as oxygen-containing gas and carbon-containing gas. It can be achieved.

[0041] The EUV mask blank of this embodiment has an absorber formed on the protective film 50 that absorbs exposure light. The reflectance of the EUV light is reduced by the absorber film 70. An absorber film 70 may be provided. The absorber film 70 is provided in contact with the metal oxide layer 55. The other main surface (rear surface) of the substrate 10, which is the surface opposite to the one main surface, is preferably is a conductive film that is in contact with the other main surface and is used to electrostatically chuck the EUV mask to the exposure tool. In this embodiment, one main surface of the substrate 10 is referred to as the front surface. The other main surface is the backside and bottom side, but the front and back and top and bottom of both are not defined for convenience. The first main surface and the second main surface are the two main surfaces (film formation surfaces) of the substrate 10. The front and back and top and bottom are interchangeable.

[0042] As described above, the buffer layer 1 is formed between the outermost Si layer 21a and the protective film 50 as a base film. 7, the SiN-containing layer 26 may be formed in the Si / Mo laminated portion 25. When the insulating film 21 is provided between the outermost Si layer 21a and the protective film 50 (metal oxide film 51), The SiN-containing layer 26 may function as a buffer layer (see FIG. 2). 140 may be made of a metal that is difficult to oxidize, such as Ru, or may be made of C, B4C, or the like.

[0043] From the EUV mask blank (mask blank for EUV exposure), the absorber film 70 is patterned. An EUV mask having an absorber pattern (pattern of the absorber film 70) formed by etching. (EUV exposure mask) is manufactured (see Figure 9). The masks are a reflective mask blank and a reflective mask.

[0044] The absorber film 70 is formed on the multilayer reflective film 20, and absorbs the EUV light, which is the exposure light, This is a film that reduces the reflectance of exposure light. In the EUV mask, an absorber film 70 is formed. The difference in reflectance between the part where the absorber film 70 is formed and the part where the absorber film 70 is not formed determines the transfer pattern. Form a circle.

[0045] The material of the absorber film 70 can be any material that can absorb EUV light and can be patterned. There is no limitation on the material of the absorber film 70. For example, tantalum (Ta) or chromium (C Materials containing Ta or Cr include materials containing oxygen (O), It may contain nitrogen (N), carbon (C), boron (B), etc. Materials containing Ta These include Ta alone, TaO, TaN, TaON, TaC, TaCN, TaCO, and TaCO N, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, T Examples of tantalum compounds that contain Cr include C rSingle, CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB , CrOB, CrNB, CrONB, CrCB, CrCNB, CrCOB, CrCONB Chromium compounds such as:

[0046] The absorber film 70 can be formed by sputtering, which is a method for forming a magneto Specifically, a chromium (Cr) target, a tantalum (Ta) target, etc. Metal targets such as chromium compound targets, tantalum compound targets, etc. Metal compound target (metals such as Cr, Ta, and oxygen (O), nitrogen (N), carbon (C) A target containing boron (B) or the like can be used. The gases used are helium (He), argon (Ar), krypton (Kr), and A rare gas such as xenon (Xe) gas can also be used, and oxygen-containing gases can also be used together with rare gases. Reactive sputtering using reactive gases such as nitrogen-containing gases and carbon-containing gases It can also be formed as follows.

[0047] On the side of the absorber film 70 away from the substrate 10, an absorber film 71 is preferably provided in contact with the absorber film 70. The hard mask film 110 has different etching characteristics from the absorber film 70 (etching of the absorber film 70). A hard mask film 110 may be provided (see FIGS. 6 and 7). This film functions as an etching mask when dry etching the body film 70. After the absorber pattern is formed on the hard mask film 110, an inspection such as a pattern inspection is performed. The absorber film 7 is left as a reflectance reducing layer to reduce the reflectance at the wavelength of light used in It may be part of 0 or may be removed so that it does not remain on the EUV mask. The hard mask film 110 may be made of a material containing chromium (Cr). The hard mask film 110 formed of a material containing Cr is particularly suitable for the absorber film 70. It is preferable that the absorber film 70 is made of a material containing Ta but not containing Cr. In addition, it mainly functions to reduce the reflectance at the wavelength of light used in inspections such as pattern inspections. A reflectance reducing layer 160 may also be formed (see FIG. 6). In this case, a hard mass The hard mask film 110 can be formed on the reflectivity-reducing layer 160. The hard mask film 110 can be formed by, for example, magnetron sputtering. There are no particular limitations on the film thickness, but it is usually about 5 to 20 nm.

[0048] The conductive film 120 provided on the back surface side preferably has a sheet resistance of 100 Ω / □ or less. The material of the conductive film 120 is, for example, tantalum (Ta). Materials containing Ta or chromium (Cr) are also available. It may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Materials that contain Ta include Ta itself, TaO, TaN, TaON, TaC, TaCN, and Ta CO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, Examples of tantalum compounds include TaCOB and TaCONB. Materials containing Cr include Specifically, Cr alone, CrO, CrN, CrON, CrC, CrCN, CrCO, Cr CON, CrB, CrOB, CrNB, CrONB, CrCB, CrCNB, CrCOB CrCONB and other chromium compounds.

[0049] The thickness of the conductive film 120 is not particularly limited as long as it functions as an electrostatic chuck. The thickness of the conductive film 120 is usually about 5 to 100 nm. That is, after forming the absorber pattern, the multilayer reflective film 20 and the absorber pattern are It is preferable to form the conductive film 120 so as to balance the thickness. The film may be formed before or after all the films on the multilayer reflective film 20 side of the substrate 10 are formed. After forming a part of the film on the multilayer reflective film 20 side of the substrate 10, the conductive film 120 is formed. Then, the remaining film on the side of the substrate 10 facing the multilayer reflective film 20 may be formed. For example, it can be formed by magnetron sputtering.

[0050] Furthermore, the EUV mask blank has a resist film 170 on the side farthest from the substrate 10. The resist film 170 may be formed by electron beam (EB) laser. A resist is preferably applied on the hard mask film 110 and the reflectivity reducing layer 160 (see FIG. 6). A resist film 170 may be formed.

[0051] Using the above-mentioned reflective mask blank, the resist film 170 is subjected to ordinary electron beam lithography. The resist pattern is then etched using a When the absorber film 70 underneath is removed by etching, the etched-off portion and the absorber film 70 are removed. An absorber pattern portion consisting of a film pattern and a resist pattern is formed. By removing the resist film pattern, a reflective mask having the basic structure is obtained (see FIG. 9). ). [Example]

[0052] The present invention will be described in detail below with reference to examples and comparative examples. is not limited to.

[0053] [Example 1] A substrate 10 made of quartz glass, 152 mm square and 6.35 mm thick, was provided with molybdenum (Mo). A silicon (Si) target and a silicon (Si) target are used, and both targets are placed in contact with the main surface of the substrate 10. While the substrate 10 is rotated, multiple layers are formed by DC pulse magnetron sputtering. Two targets can be mounted, and the targets can be mounted one at a time or both at the same time. Each target is attached to a sputtering device capable of discharging at the same time, and the substrate 10 is placed thereon. First, a silicon (Si) target was placed in the chamber while argon (Ar) gas was flowing. Power is applied to the target to form a 4 nm thick silicon (Si) layer. Next, while argon (Ar) gas was flowing into the chamber, Power is applied to the molybdenum (Mo) target to form a 3 nm thick molybdenum (Mo) layer. The application of power to the molybdenum (Mo) target was stopped. The operation of forming a layer and a molybdenum (Mo) layer was considered as one cycle, and this was repeated 40 times. After the 40th cycle, a molybdenum (Mo) layer was formed, and finally, the kettle was etched in the same manner as above. After forming a silicon (Si) layer of 3.5 nm, nitrogen (N) gas was further flowed into the chamber to form a 0. A silicon nitride film having a thickness of about 5 nm was formed to form the multilayer reflective film 20 .

[0054] Next, a zirconium (Zr) target and a niobium (Nb) target are deposited on the multilayer reflective film 20. The targets are placed opposite the main surface of the substrate 10, and the substrate 10 is rotated. Then, a metal oxide layer in contact with the multilayer reflective film 20 is formed by DC pulse magnetron sputtering. After the formation of the multilayer reflective film 20, the multilayer reflective film 2 was removed without being exposed to the atmosphere. From the sputtering device where the multilayer reflective film 20 was formed, the multilayer reflective film 20 was transferred via a transport path that maintained a vacuum state. The substrate 10 on which the film was formed was set. Two targets can be mounted, and the targets were either Each target is attached to a separate sputtering device that can discharge both simultaneously, and multiple layers are deposited. The substrate 10 on which the reflective film 20 was formed was placed. First, argon (Ar) gas was introduced into the chamber. Zirconium (Zr) turbidity was measured while flowing 15 sccm of HCl and 20 sccm of oxygen (O2) gas. A 500W power was applied to the get and niobium (Nb) target simultaneously, and a thickness of 0.5nm was obtained. A layer consisting of ZrO and NbO is formed, and then the power applied to the target is left unchanged. Then, the argon (Ar) gas was changed to 12 sccm and the oxygen (O2) gas was changed to 50 sccm. Then, a layer with a high oxygen content consisting of ZrO and NbO having a thickness of 1.5 nm was formed, and a metal oxide layer 5 I gave it a score of 5.

[0055] The composition of the protective film 50 is The layer in contact with the multilayer reflective film 20 is Zirconium (Zr) 32 atomic % Niobium (Nb) 23 atomic % The oxygen (O) content was 45 atomic %. The layer farthest from the multilayer reflective film 20 (the layer with the highest oxygen content) is Zirconium (Zr) 25.5 atomic % Niobium (Nb) 18.5 atomic % The oxygen (O) content was 56 atomic %.

[0056] Regarding the multilayer reflective film 20, the protective film 50, and the SiN layer 26 serving as a buffer layer on the substrate 10: The reflectivity of EUV light (wavelength 13-14 nm) at an incident angle of 6° was measured by euv tech. LPR-1016, a fully automated EUV mask reflectometer from Epson (same for the following reflectance measurements). The measurement was 65.0%.

[0057] In addition, the multilayer reflective film 20, the protective film 50, and the SiN layer 26, which is a buffer layer, on the substrate 10 are On the other hand, heat treatment was performed in an air atmosphere at 200°C for 15 minutes using a hot plate type heating device. After the treatment, the reflectance to EUV light at an incident angle of 6° was measured and found to be 65.2%. The difference in reflectance before and after heat treatment was 0.2%, and no decrease in reflectance due to heat treatment was observed. In fact, the reflectivity improved.

[0058] Next, the compositions of the multilayer reflective film 20 and the protective film 50 before and after the heat treatment were confirmed by XPS. The oxygen contents of the metal oxide layer 55 and the multilayer reflective film 20 remained unchanged.

[0059] [Comparative Experiment Example 1] The surface SiN layer 26 was replaced with the Si layer 21 (i.e., the SiN layer 26 was not provided). The multilayer reflective film 20 was formed in the same manner as in Experimental Example 1. Argon (Ar) gas was flowed into the chamber at 12 sccm and oxygen (O2) gas at 50 sccm. At the same time, the zirconium (Zr) target and the niobium (Nb) target were each 500 W power was applied to form a 2.0 nm thick oxygen-containing film made of ZrO and NbO, similar to that in Example 1. A layer with a high oxygen content was formed, and no layer with a low oxygen content was provided between the multilayer film.

[0060] The multilayer reflective film 20 and the protective film 50 on the substrate 10 were subjected to EUV light (wavelength 1000 nm) at an incident angle of 6°. The reflectance for the EUV mask (3 to 14 nm) was measured using euv tech.'s fully automatic reflectometer. When measured using LPR-1016 (same as in the following reflectance measurements), it was 63.8%. there were.

[0061] In addition, the multilayer reflective film 20 and the protective film 50 (buffer layer and metal oxide layer 55) on the substrate 10 Heat treatment was carried out in an air atmosphere at 200°C for 15 minutes using a hot plate type heating device. After the treatment, the reflectance to EUV light at an incident angle of 6° was measured and found to be 63.8%. The difference in reflectance before and after heat treatment was 0.0%, and no decrease in reflectance due to heat treatment was observed. It was.

[0062] Next, the compositions of the multilayer reflective film 20 and the protective film 50 before and after the heat treatment were confirmed by XPS. The oxygen content in the metal oxide layer 55 and the multilayer reflective film 20 did not change. Compared with Example 1, the oxygen content of the Si layer 21 provided on the front surface of the multilayer reflective film 20 is 35 This caused a problem in that the reflectivity decreased. This can occur.

[0063] [Comparative Example 1] The SiN layer on the surface was replaced with the Si layer 21 (i.e., the SiN layer 26 was not provided). The multilayer reflective film 20 was formed in the same manner as in Example 1. Next, ruthenium was deposited on the multilayer reflective film 20. Using a (Ru) target, DC pulse magnetron sputtering was performed while rotating the substrate 10. After the formation of the multilayer reflective film 20, a protective film was formed by tarpaulin deposition. The vacuum state is removed from the sputtering device in which the multilayer reflective film 20 was formed without being taken out into the atmosphere. The substrate 10 on which the multilayer reflective film 20 was formed was placed via the maintained transport path. While argon (Ar) gas was flowing inside, power was applied to the Ru target, and a thickness of 2.0 nm was formed. A Ru layer was formed as the protective film 50.

[0064] The multilayer reflective film 20 and the protective film 50 on the substrate 10 were subjected to EUV light (wavelength 1000 nm) at an incident angle of 6°. The reflectance for wavelengths from 3 to 14 nm was measured and found to be 65.3%.

[0065] In addition, the multilayer reflective film 20 and the protective film 50 on the substrate 10 are heated by a hot plate method. After heat treatment in air at 200°C for 15 minutes in a thermal device, EU at an incident angle of 6° The reflectance to V light was measured and found to be 59.4%, with a difference of 5% before and after heat treatment. .9%.

[0066] Next, the compositions of the multilayer reflective film 20 and the protective film 50 before and after the heat treatment were confirmed by XPS. In addition to the formation of a Ru and Si diffusion layer, oxidation of the surface layer of the multilayer reflective film 20 progressed. there was.

[0067] Comparative Example 2 The same as Experimental Example 1 except that a Mo layer 22 was formed to a thickness of 0.5 nm instead of the SiN layer on the surface. In this case, the Mo layer 22 constitutes the multilayer reflective film 20. The Mo layer 22 is formed on the outermost surface of the multilayer reflective film 20. A ruthenium (Ru) target was used on the substrate 20, and a DC pulse was applied while the substrate 10 was rotated. A protective film in contact with the multilayer reflective film 20 was formed by magnetron sputtering. After the reflective film 20 was formed, the multilayer reflective film 20 was formed by sputtering without being taken out into the atmosphere. The substrate 10 on which the multilayer reflective film 20 is formed is transported from the device via a transport path maintained in a vacuum state. While argon (Ar) gas was flowing into the chamber, power was applied to the Ru target. A Ru layer having a thickness of 2.5 nm was formed as the protective film 50.

[0068] The multilayer reflective film 20 and the protective film 50 on the substrate 10 were subjected to EUV light (wavelength 1000 nm) at an incident angle of 6°. The reflectance for wavelengths from 3 to 14 nm was measured and found to be 65.4%.

[0069] In addition, the multilayer reflective film 20 and the protective film 50 on the substrate 10 are heated by a hot plate method. After heat treatment in air at 200°C for 15 minutes in a thermal device, EU at an incident angle of 6° The reflectance to V light was measured and found to be 62.9%, with a difference of 2.0% between before and after heat treatment. .5%.

[0070] Next, the compositions of the multilayer reflective film 20 and the protective film 50 before and after the heat treatment were confirmed by XPS. The Mo layer 22 suppressed the formation of a Ru and Si diffusion layer, but the oxidation of the Mo layer 22 was underway.

[0071] Comparative Example 3 The multilayer reflective film 20 was formed in the same manner as in Comparative Example 2. As described above, in this case, the multilayer reflective film The Mo layer 22 is provided on the outermost surface of the protective film 20. A layer with a high oxygen content similar to that of Example 1 was formed, which was made of ZrO and NbO with a thickness of 2.0 nm. Ta.

[0072] The multilayer reflective film 20 and the protective film 50 on the substrate 10 were subjected to EUV light (wavelength 1000 nm) at an incident angle of 6°. The reflectance of the substrate 10 for the wavelength range of 3 to 14 nm was measured and found to be 57.2%. The multilayer reflective film 20 and the protective film 50 are heated in an air atmosphere using a hot plate type heating device. Reflectance of EUV light at an incident angle of 6° after heat treatment at 200°C for 15 minutes in an atmosphere The reflectance was measured to be 56.8%, and the difference in reflectance before and after the heat treatment was 0.4%.

[0073] In Comparative Example 3, in which a metal oxide film 51 having a different oxygen content was provided and then a Mo layer was provided on the outermost surface, Although the decrease in reflectance after heat treatment was small, the absolute value of the reflectance was small. On the other hand, in Example 1, when the metal oxide film 51 having a different oxygen content is provided, However, by placing a Si layer on the top surface instead of a Mo layer, the reflectance after heat treatment This is extremely beneficial in that high reflectance can be achieved while minimizing the decrease. [Explanation of symbols]

[0074] 10 Substrate 20 Multilayer reflective coating 25 Si / Mo laminated section 50 Protective film 51 Metal oxide film 55 Metal oxide layer 70 Absorber membrane

Claims

1. A substrate; a multilayer reflective film provided above the substrate and reflecting exposure light; a metal oxide film provided above the multilayer reflective film; an absorber film provided above the metal oxide film and absorbing exposure light; Equipped with the multilayer reflective film is formed by alternately stacking Mo layers and Si layers, and the layer farthest from the substrate is the Si layer; the metal oxide film has a higher oxygen content in a layer on a side away from the substrate than in a side on the substrate; A reflective mask blank, wherein the metal oxide film contains Nb but does not contain Ru.

2. 2. The reflective mask blank according to claim 1, wherein the metal contained in the metal oxide film is a metal having an extinction coefficient k of less than 0.02 for EUV light having a wavelength of 13.53 nm.

3. 3. The reflective mask blank according to claim 1, wherein the metal oxide film functions as an etching stopper when the absorber film is processed.

4. 4. The reflective mask blank according to claim 1, wherein the metal oxide film contains at least one element selected from the group consisting of Zr, Ti, and Y, in addition to Nb.

5. 5. The reflective mask blank according to claim 1, wherein the oxygen content of the layer of the metal oxide film on the side away from the substrate does not change by heat treatment at 120°C to 200°C.

6. 6. The reflective mask blank according to claim 1, wherein the metal oxide film consists of only Nb, Zr and O.

7. the metal oxide film has a multilayer structure, A reflective mask blank according to any one of claims 1 to 6, characterized in that the oxygen content in the second layer located on the side away from the substrate is higher than that in the first layer located on the substrate side.

8. 8. The reflective mask blank according to claim 1, wherein the oxygen content of the metal oxide film increases continuously with increasing distance from the substrate.

9. 9. The reflective mask blank according to claim 1, wherein the Si layer of the multilayer reflective film that is furthest from the substrate contains a light element other than oxygen on the metal oxide film side.

10. an oxidation prevention layer containing a light element other than oxygen on the metal oxide film side between the Si layer of the multilayer reflective film that is farthest from the substrate and the metal oxide film, 10. The reflective mask blank according to claim 1, wherein the oxidation prevention layer has a thickness of 0.2 nm or more and 3 nm or less.

11. 11. The reflective mask blank according to claim 9, wherein the light element is at least one of nitrogen, carbon, and boron.

12. 12. The reflective mask blank according to claim 1, wherein, when a first reflectance for EUV light having a wavelength of 13.53 nm before a heat treatment at 120 to 200° C. is compared with a second reflectance for EUV light having a wavelength of 13.53 nm after a heat treatment at 120 to 200° C., a change in the second reflectance from the first reflectance is 0.5% or less.

13. A method for manufacturing a reflective mask, using the reflective mask blank according to claim 1 .

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