Reflection type mask blank, and production method of reflection type 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 reflective mask. [Background technology]

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

[0003] However, the continuous miniaturization of device patterns requires the formation of even finer patterns. Therefore, the exposure light has a shorter wavelength than 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, and 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. Since a reflective optical element cannot be used, a mask for transferring a pattern is used. Reflective masks have also been proposed.

[0004] Reflective masks have a multi-layer reflective film formed on the substrate that reflects EUV light. The absorber film that absorbs EUV light is formed in a pattern on the substrate. The state before patterning (including the state where a resist film is formed) is a reflective type mask. This is called a scribing blank, and is used as the material for a reflective mask (hereafter, EUV light). A reflective mask blank that reflects light is also called an EUV mask blank. The rank is determined by the multilayer reflective film formed on a 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] Between the multilayer reflective film and the absorber film, a protective film is formed to protect the multilayer reflective film. This protective film is used for etching and patterning the absorber film. Pattern correction processing when defects are detected after turn formation, and also mask pattern formation To prevent the multilayer reflective coating from being damaged later by mask cleaning, etc. The purpose of this protective film is to protect the reflection film. As disclosed in US Pat. No. 2981 (Patent Document 1), ruthenium (Ru) is used. do. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-122981 A Summary of the Invention [Problem to be solved by the invention]

[0007] The reflective mask blank is a multilayered mask that alternates between Mo and Si layers, with the top layer being Si. A protective film mainly made of Ru is formed on the reflective film (multi-layer periodic film) to stabilize the subsequent processes. In order to achieve this, heat treatment is generally carried out at temperatures in the range of 120 to 200°C.

[0008] However, the combination of a Ru-containing protective film and a multilayer reflective film with a Si surface layer is difficult to achieve by heat treatment. The RuSi diffusion layer is formed due to the Ru film 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 light is easily transmitted and the buffer layer itself is oxidized, the reflectance is significantly reduced. If the protective film is a metal oxide film with a high oxygen content, the reflectance of the protective film can be reduced by heat treatment. While this can keep the fluctuations to a minimum, it is possible to increase the surface area of ​​the multilayer reflective film by more than necessary. This can cause the reflectance to drop significantly.

[0009] The present invention has been made in view of the above points, and is intended to provide a method for manufacturing a semiconductor device that can be used without causing any reflection even after heat treatment. Reflective mask blank with little decrease in reflectance and high reflectance maintained, 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 configured to reflect exposure light; a protective film including a metal oxide film provided on the multilayer reflective film; an absorber film provided on the protective film and configured to absorb exposure light; Equipped with The multilayer reflective film is formed by alternately laminating Mo layers and Si layers, and the side farthest from the substrate is 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 having 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 the elements 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 reduced by a heat treatment of 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 multi-layer 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 the furthest from the substrate has a metal oxide film side that is not exposed to oxygen or the like. Other light elements may also be included.

[0019] In the reflective mask blank according to the present invention, A front surface is provided between the Si layer of the multilayer reflective film that is farthest from the substrate and the metal oxide film. an oxidation inhibition 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 producing a reflective mask according to the present invention, A reflective mask may be manufactured using the above-described reflective mask blank. Effect 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 is maintained. Therefore, it is possible to realize a reflective mask blank that maintains the original shape. [Brief description of the drawings]

[0024] [Figure 1A] FIG. 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. 2 is a cross-sectional view showing another example of a reflective mask blank according to an embodiment of the present invention. [Diagram 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 multi-layer structure used in an embodiment of the present invention. [Figure 3B] 11 is a cross-sectional view showing another example of a protective film having a multi-layer structure used in an embodiment of the present invention. FIG. [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. [Diagram 5] FIG. 11 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. 2 is a cross-sectional view showing an example of a reflective mask blank having an oxidation inhibition layer, a hard mask film, a reflectance reduction layer, and a conductive film according to an embodiment of the present invention. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a reflective mask blank having an oxidation inhibition layer, a buffer layer, a hard mask film, and a conductive film according to an embodiment of the present invention. [Figure 8] FIG. 2 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 PREFERRED EMBODIMENTS

[0025] The present invention will now be described.

[0026] As shown in FIGS. 1A and 1B, the EUV mask blank according to the present 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 of the main surfaces of the substrate 10. The wavelength of EUV light used in EUV lithography as exposure light is 13 to 14 nm. Typically, the wavelength of this light is about 13.5 nm (for example, 13.4 to 13.6 nm).

[0027] The substrate 10 is preferably one having low thermal expansion characteristics for use in EUV light exposure. For example, the thermal expansion coefficient is ±2×10 -8 / ℃, preferably within ±5×10 -9 / ℃ range It is preferable that the substrate 10 is made of a material having a sufficiently flat surface. It is preferable to use a substrate having a surface roughness of 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 laminated. This is a film that reflects the EUV light, which is the exposure light. In this embodiment, the multilayer reflective film 20 is The silicon (Si) layer 21 and the molybdenum (Mo) layer 22 are alternately laminated to form a multilayer structure. The Si / Mo laminated portion 25 has a structure that is resistant to EUV light. A layer of Si (Si layer 21) which is a material having a high refractive index relative to EUV light, A layer of Mo (Mo layer 22), which is a material having a relatively low refractive index, is 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 by itself or contain less than 10 percent of other components. The number of stacked layers of the Si layer 21 and the Mo layer 22 may be, for example, 40 or more periods (40 or more layers for each). ) and preferably 60 periods or less (each 60 layers or less). 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 not more than 100 μm. 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 so as to obtain a 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 the silicon, 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 lowering 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 reflection is not impaired. It has been discovered that it is possible to produce a reflective mask blank that maintains a high reflectance with little loss of reflectance, The present invention has been made. Note that 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 53 nm. It was also confirmed that.

[0030] In this embodiment, the Si / Mo laminated portion 25 is a portion between the Si layer 21 and the Mo layer 22. At least one of the layers is formed by contacting both the Si layer 21 and the Mo layer 22 and containing Si and N. 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 A SiN-containing layer (SiN-containing layer 26) is preferred (see FIG. 2). The N content of the layer containing i and N is preferably 1 atomic % or more, and more preferably 5 atomic % or more. It is preferable that the Si content is 60 atomic % or less, and particularly preferably 57 atomic % or less. The thickness of the layer containing N is preferably 2 nm or less, 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 metal oxide film 51 may be 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 caused by the formation of a protective film is suppressed. In addition, the protective film 50 may include a film other than the metal oxide film 51 (e.g., 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 the group consisting of Zr, Nb, Ti, and Y. By adopting such an embodiment, a 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 away from the substrate 10 (typically, the layer S furthest from the substrate 10) 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. A stable layer with no change in oxygen content even when oxygen is added, particularly an oxygen-saturated state, is desirable. Here, even if heat treatment is performed at 120 to 200°C, there is no change in the oxygen content. The difference between the first state before the heat treatment from 120℃ to 200℃ and the second state after the heat treatment from 120℃ to 200℃ When compared with the case after heat treatment at 00°C (second state), the oxygen content in the second state This means that the amount of oxygen in the first state is 95 atomic % or more. When an oxygen-unsaturated layer is provided near the interface with the multilayer reflective film 20, It is possible to create a film that has little fluctuation in reflectance and maintains a high reflectance. The thickness of is 0.5 nm or more, particularly 1 nm or more, and less than 3.5 nm, particularly 3 nm or less, and It is preferable that the thickness is 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. A metal oxide layer 55 may be laminated on the substrate 10 side. 55, the oxygen content in another 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 The second metal oxide layer 55 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 continuously increase with increasing distance from the substrate 10. Also, the oxygen content in the metal oxide layer 55 gradually decreases from the substrate 10 to the Alternatively, the thickness may be increased 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, Alternatively, the protective film 50 may have a multi-layer structure as shown in FIG. 3A. The amount may be increased by atomic percent to 10 atomic percent. The film 50 is provided in only two layers, and is spaced apart from the plate 10 compared to the protective film 50 located on the substrate 10 side. The oxygen content in the protective film 50 located on the side facing the substrate may be made higher. The difference in the oxygen content in the most basic group may be about 15 atomic % to 50 atomic %. The oxygen content of the protective film 50 on the plate 10 side 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 is the one located on the side farthest from the substrate 10. 21a) may contain a light element other than oxygen on the metal oxide layer 55 side. 0, the Si layer 21 (the farthest Si layer 21a) on the side farthest from the substrate 10 and the protective film 50 An oxidation suppression layer 60 containing a light element other than oxygen may be provided between the metal oxide layer 55 and the oxidation suppression layer 60. (See Figure 6.) Light elements are 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, etc. In this case, the oxidation of the surface layer of silicon can be reduced, and a high reflectance can be maintained. The thickness of the suppression layer 60 is preferably 0.2 nm or more and 3 nm or less. The light element in this case means an element that is heavier than oxygen. Between the insulating layer 1a and the protective film 50, an oxidation suppression layer 60 and a buffer layer 140 such as a SiN-containing layer 26 are provided. 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 first reflectance to EUV light (13.53 nm) before processing 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. In this embodiment, a method for manufacturing a reflective mask is also provided.

[0038] The Si / Mo laminated portion 25 is formed by supplying power to a target. The sputtering method uses a plasma (ionization) of the atmospheric gas to perform sputtering, and the ionization method uses a plasma (ionization) of the atmospheric gas to perform sputtering. One example of the sputtering method is the ion beam sputtering method, in which an ion beam is irradiated onto a target. The DC sputtering method applies a direct current voltage to the target, and the RF sputtering method applies a high frequency voltage to the target. The sputtering method is a method in which sputtering gas is introduced into a chamber. A voltage is applied to the target, the gas is ionized, and the gas ions cause sputtering. Of the deposition methods used, magnetron sputtering in particular 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. A pulse sputtering technique in which the negative bias applied to the target is briefly reversed to prevent sputtering. This also includes

[0039] The Si / Mo laminated portion 25 is formed, for example, by using a sputtering device capable of mounting multiple 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 sputtered sequentially 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 chromium deposition, similar to the multilayer reflective film 20. The film can be formed by magnetron sputtering. The target is a metal material used for the protective film 50. The sputtering gas used was helium (He), argon (Ar), and crypto Rare gases such as fluorine (Kr) gas and xenon (Xe) gas, and oxygen-containing gases and nitrogen (N) gases as necessary. The material is formed by sputtering using reactive gases such as nitrogen-containing gas and carbon-containing gas. It can be achieved.

[0041] The EUV mask blank of this embodiment has an absorber formed on a protective film 50 that absorbs exposure light. More specifically, the absorber film 70 may have an absorber film that absorbs EUV light and reduces reflectance. 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 of the substrate 10, 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 of the main surfaces of the substrate 10 is called the front surface. The other main surface is the back side and the bottom side, but the front and back and the top and bottom are not defined for the sake of convenience. The first main surface and the second main surface are the two main surfaces (film-forming surfaces) of the substrate 10. The front and back and top and bottom are interchangeable.

[0042] As described above, the buffer layer 1, which is a base film, is provided between the outermost Si layer 21a and the protective film 50. 40 may be provided (see FIG. 7). Note that the SiN-containing layer 26 is a 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 portion where the absorber film 70 is formed and the portion 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. The material of the absorber film 70 is, for example, tantalum (Ta) or chromium (C Materials containing Ta or Cr include oxygen (O), It may contain nitrogen (N), carbon (C), boron (B), etc. Materials containing Ta The following are 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 Examples of chromium compounds include those mentioned above.

[0046] The absorber film 70 can be formed by sputtering, which is a method for forming a magnetron. Specifically, a chromium (Cr) target, a tantalum (Ta) target, and a tantalum (Ta) target are preferably used. 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, for example, boron (B) can be used. As gas, helium (He) gas, argon (Ar) gas, krypton (Kr) gas, A rare gas such as xenon (Xe) gas can also be used, and oxygen-containing gases can also be used together with the rare gas. Reactive sputtering using reactive gases such as nitrogen-containing gas, carbon-containing gas, etc. It is also possible to form

[0047] On the side of the absorber film 70 away from the substrate 10, an absorber film 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 FIG. 6 and FIG. 7). This film functions as an etching mask when dry etching the substrate film 70. After the absorber pattern is formed, the hard mask film 110 is inspected, for example, by a pattern inspection. 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). In the hard mask film 110 formed of a material containing Cr, in particular, the absorber film 70 is It is preferable that the absorber film 70 is made of a material that contains Ta and does not contain Cr. In addition, the main function of the device is to reduce the reflectance at the wavelength of light used in inspections such as pattern inspection. A layer (reflectance reducing layer) 160 may be formed (see FIG. 6). In this case, a hard mass is used. The hard mask film 110 may be formed on the reflectance reducing layer 160. The hard mask film 110 can be formed by, for example, magnetron sputtering. There is no particular limitation on the thickness of the film, 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 conductive film 120 may be made of any material, and there is no particular limitation on the material. Materials containing Ta or chromium (Cr) are also available. Materials containing Ta or Cr are also It may contain oxygen (O), nitrogen (N), carbon (C), boron (B), etc. Materials that contain Ta include 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 the absorber pattern is formed, 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 of the conductive film 120. The insulating layer 14 may be formed before or after all the films on the multilayer reflective film 20 side of the substrate 10 are formed. Also, 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 multilayer reflective film 20 of the substrate 10 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 used. A resist is applied on the hard mask film 110 and the reflectance reducing layer 160 (see FIG. 6). A gyros membrane 170 may be formed.

[0051] Using the above-mentioned reflective mask blank, the resist film 170 is subjected to normal electron beam lithography. The resist pattern is then etched using a When the absorber film 70 underneath is etched away, the etched away portion and the absorber film 70 are 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). ). EXAMPLES

[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 having a size of 152 mm square and a thickness of 6.35 mm is provided with molybdenum (Mo). A silicon (Si) target and a silicon (Si) target are used, and the targets are placed against the main surface of the substrate 10. While the substrate 10 is rotated, multiple layers are formed by DC pulse magnetron sputtering. A layered reflective film 20 was formed. Two targets can be mounted, and the targets can be either one at a time or both at the same time. Each target was attached to a sputtering device capable of discharging at a time, and the substrate 10 was placed thereon. First, a silicon (Si) target was placed in the chamber while argon (Ar) gas was flowing. Electricity was applied to the target to form a 4 nm thick silicon (Si) layer, and the silicon (Si) target The power supply to the chamber was stopped. Next, argon (Ar) gas was allowed to flow 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 then stopped. The operation of forming a layer and a molybdenum (Mo) layer was counted as one cycle, and this cycle was repeated 40 times. After the 40th cycle, the molybdenum (Mo) layer was formed, and finally, the kettle was sintered in the above manner. 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 layer 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 formed on the multilayer reflective film 20. The targets are placed opposite the main surface of the substrate 10 while 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 255 was formed without being taken out into the atmosphere. The multilayer reflective film 20 is transferred from the sputtering device in which the multilayer reflective film 20 was formed via a transport path maintained in a vacuum state. The substrate 10 on which the film was formed was set. Two targets can be attached, and the targets were either Each target is attached to a separate sputtering device that can discharge both targets 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) turbulence was performed while flowing 15 sccm of nitrogen and 20 sccm of oxygen (O2) gas. A power of 500 W was applied to the get and the niobium (Nb) target simultaneously, and a thickness of 0.5 nm was obtained. A layer of ZrO and NbO was formed, and the power applied to the target was then kept constant. Then, the argon (Ar) gas was changed to 12 sccm and the oxygen (O2) gas was changed to 50 sccm. Then, a layer having a high oxygen content and made of ZrO and NbO having a thickness of 1.5 nm is 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 furthest 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 reflectance for EUV light (wavelength 13-14 nm) with an incident angle of 6° was measured by euv tech. LPR-1016, an automatic EUV mask reflectometer from Epson (same for all reflectance measurements below). The measured value 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 In contrast, the product was heat-treated in air at 200°C for 15 minutes using a hot plate heating device. After the treatment, the reflectance of the EUV light with an incident angle of 6° was measured and found to be 65.2%. The difference in reflectance before and after the heat treatment was 0.2%, and no decrease in reflectance due to the heat treatment was observed. In fact, the reflectance was 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 coating 20 did not change.

[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 was flowed 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 similar to that of Example 1, which is made of ZrO and NbO. 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 irradiated with EUV light (wavelength 1 The reflectance for the EUV mask (3~14 nm) was measured using euv tech.'s EUV mask fully automatic reflectance meter. When measured using the LPR-1016 (same as in the following reflectance measurements), the result 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 performed in air at 200°C for 15 minutes using a hot plate heating device. After the treatment, the reflectance of the EUV light at an incident angle of 6° was measured and found to be 63.8%. The difference in reflectance before and after the heat treatment was 0.0%, and no decrease in reflectance due to the 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 reflectance decreased. This can occur.

[0063] [Comparative Example 1] The experiment was conducted except that the surface SiN layer 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, the substrate 10 was rotated and subjected to DC pulse magnetron spalling. A protective film was formed by tarpaulin deposition in contact with the multilayer reflective film 20. After the multilayer reflective film 20 was formed, The vacuum state is removed from the sputtering apparatus 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 flowing argon (Ar) gas inside the chamber, 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 irradiated with EUV light (wavelength 1 The reflectance for the wavelength range of 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 incidence angle of 6° The reflectance against V light was measured and found to be 59.4%, with a difference of 5% between 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, the oxidation of the surface layer of the multilayer reflective film 20 progressed. there was.

[0067] [Comparative Example 2] The same as in 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. Argon (Ar) gas was flowing into the chamber while applying power 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 irradiated with EUV light (wavelength 1 The reflectance for the wavelength range of 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 incidence angle of 6° The reflectance against V light was measured and found to be 62.9%, with the difference in reflectance before and after heat treatment being 2. .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 diffusion layer of Ru and Si, 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 irradiated with EUV light (wavelength 1 The reflectance of the substrate 10 was measured for a wavelength of 3 to 14 nm and was 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 air atmosphere The reflectance was measured and found to be 56.8%, with the difference in reflectance before and after the heat treatment being 0.4%.

[0073] In Comparative Example 3, 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 the first embodiment, 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 a high reflectance can be achieved while minimizing the degradation. [Explanation of symbols]

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

Claims

1. A substrate; a multilayer reflective film provided on the substrate and configured to reflect exposure light; a protective film including a metal oxide film provided on the multilayer reflective film; an absorber film provided on the protective film and configured to absorb exposure light; Equipped with The multilayer reflective film is formed by alternately laminating Mo layers and Si layers, and the side farthest from the substrate is 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. A reflective mask blank characterized by a high amount.

2. The metal contained in the metal oxide film has an extinction coefficient of 13.53 nm for EUV light.

2. The reflective mask blank according to claim 1, which is made of a metal having k of less than 0.

02. nine.

3. The protective film functions as an etching stopper when processing the absorber film. The reflective mask blank according to claim 1 or 2.

4. The metal oxide film contains one or more elements selected from the group consisting of Zr, Nb, Ti, and Y. The reflective mask blank according to claim 1 ,

5. The oxygen content of the layer of the metal oxide film on the side away from the substrate is reduced by heat treatment at 120° C. to 200° C.

5. The reflective mask blanking device according to claim 1, wherein the reflection-type mask blanking device does not change due to a change in the reflection-type mask blanking device. Rank.

6. 4. The metal oxide film according to claim 3, wherein the thickness of the metal oxide film is 0.5 nm or more and less than 3.5 nm.

6. A reflective mask blank according to any one of items 1 to 5.

7. The metal oxide film has a multi-layer structure, In comparison with the first layer located on the substrate side, 7. The reflective type according to claim 1, wherein the oxygen content in the reflective type is increased. Mask blank.

8. The oxygen content of the metal oxide film increases continuously with increasing distance from the substrate.

8. The reflective mask blank according to claim 1 ,

9. The Si layer of the multilayer reflective film that is the furthest from the substrate has a metal oxide film side that is not exposed to oxygen or the like.

9. A reflective mass according to claim 1, further comprising other light elements. Kublank.

10. A front surface is provided between the Si layer of the multilayer reflective film that is farthest from the substrate and the metal oxide film. an oxidation inhibition layer containing a light element other than oxygen on the metal oxide film side; 2. The oxidation prevention layer according to claim 1, wherein the thickness of the oxidation prevention layer is 0.2 nm or more and 3 nm or less.

10. A reflective mask blank according to any one of claims 1 to 9.

11. 2. The method according to claim 1, wherein the light element is at least one of nitrogen, carbon, and boron.

11. A reflective mask blank according to any one of 9 or 10.

12. For EUV light having a wavelength of 13.53 nm before heat treatment at 120 to 200 ° C. EU having a first reflectance and a wavelength of 13.53 nm after heat treatment at 120 to 200° C. When compared with the second reflectance for V light, the change in the second reflectance relative to the first reflectance is 0.

12. The reflective mask according to claim 1, wherein the difference is 5% or less. blank.

13. A reflective mask is formed by using the reflective mask blank according to any one of claims 1 to 12. A method for manufacturing a reflective mask.

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