JP2019219651A - Reflection type mask blank, reflection type mask, and method for producing reflection type mask blank - Google Patents

Abstract

To provide a reflection type mask blank in which the surface of an absorption layer is oxidized and the generation of defect on the surface of the absorption layer can be suppressed.SOLUTION: The reflection type mask blank 10A is a reflection type mask blank having, on a substrate 11, a reflection layer 12 for reflecting EUV light, and an absorption layer 14 for absorbing EUV light in this order from the substrate side, and in which the absorption layer 14 contains Sn and has, on the absorption layer 14, a prevention layer 15 for preventing the oxidation of the absorption layer 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reflective mask blank, a reflective mask, and a method for manufacturing a reflective mask blank.

  In recent years, with the miniaturization of integrated circuits constituting semiconductor devices, an extreme exposure method has been used as an alternative to the conventional exposure technology using visible light, ultraviolet light (wavelength 193 to 365 nm), ArF excimer laser light (wavelength 193 nm), or the like. Ultraviolet (Etreme Ultra Violet: hereinafter, referred to as “EUV”) lithography is being studied.

  In EUV lithography, EUV light having a shorter wavelength than ArF excimer laser light is used as a light source used for exposure. EUV light refers to light having a wavelength in a soft X-ray region or a vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm. As the EUV light, for example, EUV light having a wavelength of about 13.5 nm is used.

  Since EUV light is easily absorbed by any substance, a refractive optical system used in the conventional exposure technology cannot be used. Therefore, in EUV lithography, a reflective optical system such as a reflective mask or a mirror is used. In EUV lithography, a reflective mask is used as a transfer mask.

  In the reflection type mask, a reflection layer that reflects EUV light is formed on a substrate, and an absorption layer that absorbs EUV light is formed in a pattern on the reflection layer. The reflection type mask was formed in a predetermined pattern by removing a part of the absorption layer using a reflection type mask blank constituted by laminating a reflection layer and an absorption layer on the substrate in this order from the substrate side as an original plate. Thereafter, it is obtained by washing with a washing solution.

  EUV light incident on the reflective mask is absorbed by the absorption layer and reflected by the reflection layer. The reflected EUV light is imaged on the surface of an exposure material (a wafer coated with a resist) by an optical system. Thereby, the pattern of the absorption layer is transferred to the surface of the exposure material.

  In EUV lithography, EUV light normally enters a reflective mask from a direction inclined at about 6 °, and is similarly reflected obliquely. Therefore, if the thickness of the absorption layer is large, the optical path of the EUV light may be blocked (shadowing). If a shadowed portion of the absorption layer is formed on the substrate or the like due to the influence of shadowing, the pattern of the reflective mask is not faithfully transferred onto the surface of the exposure material, and pattern accuracy may be degraded. On the other hand, when the thickness of the absorbing layer is reduced, the light-shielding performance of the reflective mask with respect to EUV light is reduced and the reflectivity of EUV light is increased, so that the contrast between the pattern portion of the reflective mask and other portions is reduced. May decrease.

  Therefore, a reflective mask blank that suppresses a decrease in contrast while faithfully transferring the pattern of the reflective mask has been studied. For example, Patent Literature 1 discloses that an absorber film contains Ta as a main component at 50 atomic% (at%) or more, and further contains Te, Sb, Pt, I, Bi, Ir, Os, W, Re, Sn, and In. , Po, Fe, Au, Hg, Ga and Al are described as reflective mask blanks composed of a material containing at least one element selected from the group consisting of Ga, Al, and Al.

  However, in the reflective mask blank described in Patent Document 1, there is a possibility that the surface of the absorber film is oxidized to generate fine particles on the surface of the absorber film, and defects are generated on the surface of the absorber film. For example, when the absorber film is formed of an alloy of Ta and Sn, the surface of the absorber film may be oxidized, and fine particles of tin oxide may be generated on the surface of the absorber film. When fine particles are present at a location where the absorber film should be removed by dry etching when producing a reflective mask, there is a possibility that the absorber film remains without being etched at this portion, resulting in a pattern defect. In this case, the pattern defect on the reflective mask is undesirably transferred to the exposure material (resist) applied to the wafer during wafer exposure.

JP 2007-273678 A

  An object of one embodiment of the present invention is to provide a reflective mask blank that can suppress generation of defects on the surface of the absorption layer due to oxidation of the surface of the absorption layer.

  One embodiment of the reflective mask blank according to the present invention is a reflective mask blank having, on a substrate, a reflective layer that reflects EUV light, and an absorbing layer that absorbs EUV light in this order from the substrate side, The absorption layer contains Sn, and has a prevention layer on the absorption layer to prevent oxidation of the absorption layer.

  According to one embodiment of the present invention, it is possible to provide a reflective mask blank that can suppress generation of defects on the surface of the absorption layer due to oxidation of the surface of the absorption layer.

FIG. 2 is a schematic cross-sectional view of the reflective mask blank according to the first embodiment. It is a flowchart which shows an example of the manufacturing method of a reflective mask blank. It is an outline sectional view showing an example of other forms of a reflective mask blank. It is an outline sectional view showing an example of other forms of a reflective mask blank. FIG. 3 is a schematic cross-sectional view illustrating an example of the configuration of a reflective mask. It is a figure explaining a manufacturing process of a reflective mask. It is a schematic sectional drawing of the reflective mask blank which concerns on 2nd Embodiment. It is an outline sectional view showing an example of other forms of a reflective mask blank. FIG. 3 is a schematic sectional view of a reflective mask blank of Comparative Example 1. FIG. 9 is a diagram showing the results of observation of the surface of the absorption layer of the reflective mask blank of Comparative Example 1. FIG. 4 is a diagram showing the observation results of the surface of the absorption layer of the reflective mask blank of Example 1. FIG. 9 is a diagram showing the results of observation of the surface of the absorption layer of the reflective mask blank of Example 2.

  Hereinafter, embodiments of the present invention will be described in detail. To facilitate understanding of the description, the same reference numerals are given to the same components in each drawing, and redundant description will be omitted. Also, the scale of each member in the drawings may be different from the actual one. In this specification, a coordinate on the main surface of the substrate is defined as an X-axis direction and a Y-axis direction using a three-dimensional orthogonal coordinate system of three-axis directions (X-axis direction, Y-axis direction, and Z-axis direction). Thickness direction) is defined as the Z-axis direction. The direction from the bottom to the top of the substrate (the direction from the main surface of the substrate toward the reflection layer) is defined as + Z-axis direction, and the opposite direction is defined as -Z-axis direction. In the following description, the + Z axis direction may be referred to as “up”, and the −Z axis direction may be referred to as “down”. In the present specification, a tilde “to” indicating a numerical range means that the numerical values described before and after the tilde “」 ”include the lower limit and the upper limit unless otherwise specified.

<Reflective mask blank>
The reflective mask blank according to the first embodiment will be described. FIG. 1 is a schematic sectional view of the reflective mask blank according to the first embodiment. As shown in FIG. 1, the reflective mask blank 10 </ b> A is configured such that a reflective layer 12, a protective layer 13, an absorption layer 14, and a prevention layer 15 are laminated on a substrate 11 in this order.

(substrate)
The substrate 11 preferably has a small coefficient of thermal expansion. When the thermal expansion coefficient of the substrate 11 is smaller, distortion of a pattern formed on the absorption layer 14 due to heat at the time of exposure to EUV light can be suppressed. Specifically, the thermal expansion coefficient of the substrate 11 at 20 ° C. is preferably 0 ± 1.0 × 10 ⁻⁷ / ° C., and more preferably 0 ± 0.3 × 10 ⁻⁷ / ° C.

As a material having a small coefficient of thermal expansion, for example, SiO ₂ —TiO ₂ glass or the like can be used. SiO ₂ -TiO ₂ based glass, a SiO ₂ 90 wt% to 95 wt%, it is preferable to use a quartz glass containing TiO ₂ 5 to 10% by mass. When the content of TiO ₂ is 5% by mass to 10% by mass, the coefficient of linear expansion near room temperature is substantially zero, and almost no dimensional change occurs near room temperature. Note that the SiO ₂ —TiO ₂ glass may contain a trace component other than SiO ₂ and TiO ₂ .

  It is preferable that the first main surface 11a of the substrate 11 on the side on which the reflective layer 12 is laminated has high smoothness. The smoothness of the first main surface 11a can be evaluated based on the surface roughness obtained by measuring with the atomic force microscope. The surface roughness of the first main surface 11a is preferably a root-mean-square roughness Rq of 0.15 nm or less.

  It is preferable that the first main surface 11a is processed to have a predetermined flatness. This is because the reflective mask obtains high pattern transfer accuracy and position accuracy. The substrate 11 preferably has a flatness of 100 nm or less, more preferably 50 nm or less, and still more preferably 30 nm or less in a predetermined region (for example, a 132 mm × 132 mm region) of the first main surface 11 a. .

  Further, it is preferable that the substrate 11 has resistance to a cleaning liquid used for cleaning the reflective mask blank, the reflective mask blank after pattern formation, or the reflective mask.

  Further, the substrate 11 preferably has high rigidity in order to prevent a film (such as the reflective layer 12) formed on the substrate 11 from being deformed by a film stress. For example, the substrate 11 preferably has a high Young's modulus of 65 GPa or more.

  The size, thickness, and the like of the substrate 11 are appropriately determined based on design values of the reflective mask.

  The first main surface 11a of the substrate 11 is formed in a rectangular or circular shape in plan view. In this specification, the rectangle includes a rectangle and a square, and a shape in which a corner of a rectangle and a square are rounded.

(Reflective layer)
The reflection layer 12 has a high reflectance for EUV light. Specifically, when EUV light enters the surface of the reflective layer 12 at an incident angle of 6 °, the maximum value of the reflectance of EUV light near a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% or more. preferable. Similarly, even when the protective layer 13 and the absorption layer 14 are stacked on the reflection layer 12, the maximum value of the reflectance of EUV light near the wavelength of 13.5 nm is preferably 60% or more, and 65% or more. % Or more is more preferable.

  The reflection layer 12 is a multilayer film in which a plurality of layers mainly composed of elements having different refractive indexes are periodically laminated. In general, the reflective layer 12 is a multilayer in which a plurality of high refractive index layers having a high refractive index with respect to EUV light and low refractive index layers having a low refractive index with respect to EUV light are alternately stacked from the substrate 11 side. A reflective film is used.

  The multilayer reflective film may have a multilayer structure in which a high refractive index layer and a low refractive index layer are stacked in this order from the substrate 11 side as one cycle, and may be stacked a plurality of times, or a low refractive index layer and a high refractive index layer may be stacked. A plurality of cycles may be stacked with the stacked structure stacked in this order as one cycle. In this case, it is preferable that the outermost surface layer (uppermost layer) of the multilayer reflective film be a high refractive index layer. This is because the low-refractive-index layer is easily oxidized, and if the low-refractive-index layer is the uppermost layer of the reflective layer 12, the reflectivity of the reflective layer 12 may decrease.

  As the high refractive index layer, a layer containing Si can be used. As a material containing Si, a Si compound containing at least one selected from the group consisting of B, C, N and O in addition to Si can be used. By using a high-refractive-index layer containing Si, a reflective mask excellent in EUV light reflectance can be obtained. As the low refractive index layer, a metal selected from the group consisting of Mo, Ru, Rh and Pt or an alloy thereof can be used. In this embodiment, the low refractive index layer is preferably a layer containing Mo, and the high refractive index layer is preferably a layer containing Si. In this case, by forming the uppermost layer of the reflective layer 12 as a high refractive index layer (a layer containing Si), Si and O are contained between the uppermost layer (a layer containing Si) and the protective layer 13. A silicon oxide layer is formed to improve the cleaning resistance of the reflective mask.

  Although the reflective layer 12 includes a plurality of high refractive index layers and a plurality of low refractive index layers, the thickness of the high refractive index layers or the thickness of the low refractive index layers may not be necessarily the same.

  The thickness and cycle of each layer constituting the reflective layer 12 can be appropriately selected depending on the film material to be used, the reflectance of EUV light required for the reflective layer 12 or the wavelength (exposure wavelength) of EUV light. For example, when the reflective layer 12 has a maximum value of the reflectance of EUV light having a wavelength of about 13.5 nm of 60% or more, a low refractive index layer (a layer containing Mo) and a high refractive index layer (a layer containing Si) are used. Are alternately stacked for 30 to 60 periods, and a Mo / Si multilayer reflective film is preferably used.

  Note that each layer constituting the reflective layer 12 can be formed to a desired film thickness using a known film formation method such as a magnetron sputtering method or an ion beam sputtering method. For example, when the reflective layer 12 is formed by using an ion beam sputtering method, the reflective layer 12 is formed by supplying ion particles from an ion source to a target of a high refractive index material and a target of a low refractive index material. When the reflective layer 12 is a Mo / Si multilayer reflective film, a layer containing Si having a predetermined thickness is first formed on the substrate 11 by, for example, an Si target using an ion beam sputtering method. After that, a layer containing Mo having a predetermined thickness is formed using a Mo target. By stacking the Si-containing layer and the Mo-containing layer as one cycle for 30 to 60 cycles, a Mo / Si multilayer reflective film is formed.

(Protective layer)
The protective layer 13 forms an absorber pattern 141 (see FIG. 5) on the absorbing layer 14 by etching (usually, dry etching) the absorbing layer 14 when a reflective mask 20 (see FIG. 5) described later is manufactured. At this time, the surface of the reflective layer 12 is prevented from being damaged by etching, and the reflective layer 12 is protected. In addition, the resist layer 19 (see FIG. 6) remaining on the reflective mask blank after the etching is removed with a cleaning liquid to protect the reflective layer 12 from the cleaning liquid when cleaning the reflective mask blank. Therefore, the reflectance of the obtained reflective mask 20 (see FIG. 5) with respect to EUV light is improved.

  FIG. 1 shows a case where the protective layer 13 has one layer, but the protective layer 13 may have a plurality of layers.

As a material for forming the protective layer 13, a material that is not easily damaged by etching when the absorbing layer 14 is etched is selected. As a substance satisfying this condition, for example, Ru alone or Ru contains one or more metals selected from the group consisting of B, Si, Ti, Nb, Mo, Zr, Y, La, Co and Re. Ru alloys, Ru-based materials such as nitrides containing nitrogen in Ru alloys; Cr, Al, Ta and nitrides containing nitrogen in them; SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ or mixtures thereof Is exemplified. Among them, Ru metal simple substance and Ru alloy, CrN and SiO ₂ are preferable. Ru metal simple substance and Ru alloy are particularly preferable because they are hardly etched by a gas containing no oxygen and function as an etching stopper at the time of processing a reflective mask.

  When the protective layer 13 is formed of a Ru alloy, the Ru content in the Ru alloy is preferably 95 at% or more and less than 100 at%. When the Ru content is within the above range, when the reflective layer 12 is a Mo / Si multilayer reflective film, diffusion of Si from the Si layer of the reflective layer 12 to the protective layer 13 can be suppressed. In addition, the protective layer 13 can have a function as an etching stopper when the absorption layer 14 is etched while ensuring a sufficient EUV light reflectance. Further, it is possible to provide the reflection type mask with cleaning resistance and prevent the reflection layer 12 from deteriorating with time.

  The thickness of the protective layer 13 is not particularly limited as long as it can function as the protective layer 13. In order to maintain the reflectance of the EUV light reflected by the reflective layer 12, the thickness of the protective layer 13 is preferably 1 nm or more, more preferably 1.5 nm or more, and even more preferably 2 nm or more. The thickness of the protective layer 13 is preferably 8 nm or less, more preferably 6 nm or less, and even more preferably 5 nm or less.

  As a method for forming the protective layer 13, a known film forming method such as a magnetron sputtering method or an ion beam sputtering method can be used.

(Absorbing layer)
In order to use the absorption layer 14 as a reflective mask for EUV lithography, the absorption layer 14 needs to have characteristics such as a high absorption coefficient of EUV light, easy etching, and high cleaning resistance to a cleaning liquid.

  The absorption layer 14 absorbs EUV light and has a very low EUV light reflectance. Specifically, when EUV light is applied to the surface of the absorption layer 14, the maximum value of the reflectance of EUV light near a wavelength of 13.5 nm is preferably 2% or less, more preferably 1% or less. Therefore, the absorption layer 14 needs to have a high EUV light absorption coefficient.

Further, the absorption layer 14 is processed by etching by dry etching using a chlorine (Cl) -based gas such as Cl ₂ , SiCl ₄ and CHCl ₃ or a fluorine (F) -based gas such as CF ₄ and CHF _3. . Therefore, the absorbing layer 14 needs to be easily etched.

  Further, the absorbing layer 14 is used to remove the resist pattern 191 (see FIG. 6) remaining on the reflective mask blank after etching with a cleaning liquid when manufacturing a reflective mask 20 (see FIG. 5) described later. Exposed to At that time, as the cleaning liquid, sulfuric acid peroxide (SPM), sulfuric acid, ammonia, ammonia peroxide (APM), OH radical cleaning water, ozone water and the like are used. In EUV lithography, SPM is generally used as a resist cleaning liquid. The SPM is a solution in which sulfuric acid and hydrogen peroxide are mixed, for example, a solution in which sulfuric acid and hydrogen peroxide are mixed at a volume ratio of 3: 1. At this time, the temperature of the SPM is preferably controlled to 100 ° C. or higher from the viewpoint of improving the etching rate. Therefore, the absorption layer 14 needs to have high cleaning resistance to the cleaning liquid. For example, the absorbing layer 14 preferably has a low etching rate (for example, 0.10 nm / min or less) when immersed in a solution of 75 vol% sulfuric acid and 25 vol% hydrogen peroxide at 100 ° C.

  In order to achieve the above characteristics, the absorbing layer 14 contains Sn. Since Sn has a large absorption coefficient, the reflectance of the absorption layer 14 can be reduced by including Sn in the absorption layer 14. Further, since the absorption layer 14 contains Sn, it can be easily etched with a Cl-based gas or the like.

  The absorption layer 14 preferably contains Ta, Cr or Ti in addition to Sn. These elements may be used alone or in combination of two or more. The absorbing layer 14 further includes one or more of these elements in addition to Sn to improve the cleaning resistance.

  The absorption layer 14 may further contain N, B, Hf, or H in addition to Sn. These elements may be used alone or in combination of two or more. In particular, the absorbing layer 14 preferably contains at least one of N and B among these elements. By including at least one of N and B, the absorbing layer 14 can change the crystalline state of the absorbing layer 14 to an amorphous or microcrystalline structure.

  A preferred composition of the absorbing layer 14 is, for example, SnTa, SnTaN, SnTaB or SnTaBN.

  It is preferable that the crystalline state of the absorption layer 14 is amorphous. Thereby, the absorption layer 14 can have excellent smoothness and flatness. Further, by improving the smoothness and flatness of the absorber layer 14, the edge roughness of the absorber pattern 141 (see FIG. 5) is reduced, and the dimensional accuracy of the absorber pattern 141 (see FIG. 5) can be increased.

  The absorption layer 14 may be a single-layer film or a multilayer film including a plurality of films. When the absorption layer 14 is a single-layer film, the number of steps in manufacturing a mask blank can be reduced, and the production efficiency can be improved. When the absorption layer 14 is a multilayer film, the upper layer of the absorption layer 14 can be set to the absorber pattern by using the inspection light by appropriately setting the optical constant and the film thickness of the upper layer of the absorption layer 14. 141 (see FIG. 5) can be used as an anti-reflection film when inspecting. Thereby, the inspection sensitivity at the time of inspecting the absorber pattern can be improved.

  The thickness of the absorbing layer 14 can be appropriately designed depending on the composition of the absorbing layer 14 and the like, but is preferably thinner from the viewpoint of suppressing the influence of shadowing. The thickness of the absorbing layer 14 is preferably, for example, 40 nm or less from the viewpoint of obtaining a sufficient contrast while maintaining the reflectance of the absorbing layer 14 at 1% or less. The thickness of the absorbing layer 14 is more preferably 35 nm or less, further preferably 30 nm or less, further preferably 25 nm or less, and particularly preferably 20 nm or less. The thickness of the absorbing layer 14 is determined by the reflectance, and the thinner the better. The film thickness of the absorption layer 14 can be measured using, for example, an X-ray reflectivity method (XRR), TEM, or the like.

  The absorption layer 14 can be formed using a known film formation method such as a magnetron sputtering method or an ion beam sputtering method. For example, in the case where an SnTa film is formed as the absorption layer 14 using a magnetron sputtering method, the absorption layer 14 can be formed by a sputtering method using an Ar gas using a target containing Sn and Ta. The absorption layer 14 can also be formed by a binary sputtering method using a Sn target and a Ta target simultaneously.

(Prevention layer)
The prevention layer 15 is formed on the main surface above the absorption layer 14 (in the + Z-axis direction).

  Ta, Ru, Cr, Ti, or Si can be used as a material for forming the prevention layer 15. These elements may be included alone or in combination of two or more.

  The prevention layer 15 is composed of Ta alone, Ru alone, Cr alone, Ti alone, Si alone, nitride of Ta, nitride of Ru, nitride of Cr, nitride of Ti, nitride of Si, boride of Ta, Ru boride, Cr boride, Ti boride, Si boride, or Ta boron nitride can be used. These may be included alone or in combination of two or more.

  A preferred composition of the prevention layer 15 is, for example, Ta, TaN, TaB, or TaBN. For example, as will be described later, it is assumed that a reflective mask blank 10B (see FIG. 7) according to the second embodiment having the stable layer 21 on the prevention layer 15 is formed. Then, it is assumed that the stable layer 21 contains an oxide, an oxynitride or an acid boride containing Ta. In this case, when the prevention layer 15 is made of these materials, the same target can be used when forming the prevention layer 15 and the stable layer 21. Therefore, the productivity of the reflective mask blank 10B (see FIG. 7) is excellent, for example, the number of necessary film forming chambers can be reduced.

  The prevention layer 15 may further include an element such as He, Ne, Ar, Kr, or Xe.

  The prevention layer 15 is a layer that does not contain Sn and oxygen. The phrase “not containing Sn and oxygen” means that immediately after the prevention layer 15 is formed, Sn and oxygen do not exist on the surface and inside of the prevention layer 15. When the prevention layer 15 is exposed to an atmosphere containing oxygen, the components included in the prevention layer 15 react (oxidize) with oxygen on the surface where the prevention layer 15 comes into contact with oxygen. An oxide film may be formed. At this time, if Sn is contained in the prevention layer 15, Sn present on the surface of the prevention layer 15 reacts with oxygen, and fine particles containing Sn such as tin oxide precipitate on the surface of the prevention layer 15. The prevention layer 15 does not contain Sn because it may be generated as an object.

  It should be noted that the prevention layer 15 does not contain oxygen means that in the step after the formation of the prevention layer 15, when there is an oxide film generated on the surface where the prevention layer 15 is in contact with oxygen, the oxide film Does not include oxygen. On the other hand, since the interface between the absorption layer 14 and the prevention layer 15 does not come into contact with oxygen, the interface between the prevention layer 15 and the absorption layer 14 does not contain oxygen.

  The prevention layer 15 can be formed in an inert gas atmosphere or a gas atmosphere in which nitrogen is selectively added to an inert gas using a known film forming method such as a magnetron sputtering method or an ion beam sputtering method. For example, when a Ta film, a Ru film, a Cr film, or a Si film is formed using the magnetron sputtering method as the prevention layer 15, a target containing Ta, Ru, Cr, or Si is used, and He, Ar, or The prevention layer 15 is formed by using an inert gas such as Kr or a gas in which nitrogen is selectively added to the inert gas.

  If the thickness of the prevention layer 15 is too large, it takes time to etch the prevention layer 15. Further, shadowing or the like may increase. On the other hand, if the prevention layer 15 is too thin, the function as the prevention layer 15 may not be stably and sufficiently exhibited. Therefore, the thickness of the prevention layer 15 may be about several nm from the viewpoint of suppressing the thickness of the pattern of the reflective mask blank 10A, and is preferably 10 nm or less. The thickness of the prevention layer 15 is more preferably 8 nm or less, further preferably 6 nm or less, further preferably 5 nm or less, and particularly preferably 4 nm. The thickness of the prevention layer 15 is more preferably 0.5 nm or more, still more preferably 1 nm or more, further preferably 1.5 nm or more, and particularly preferably 2 nm or more. The thickness of the prevention layer 15 can be measured using, for example, XRR or TEM.

  Thus, the reflective mask blank 10A has the prevention layer 15 on the absorption layer 14 containing Sn. It can be formed when the absorption layer 14 comes into contact with oxygen. As a result, the surface of the absorption layer 14 is oxidized, and precipitates on the surface of the absorption layer 14 and some Sn present on the surface of the absorption layer 14 react with oxygen to oxidize the surface of the absorption layer 14. Fine particles containing Sn or the like containing Sn may be generated as precipitates. As described above, the prevention layer 15 is formed on the absorption layer 14 by using only an inert gas such as He, Ar, or Kr, or a gas obtained by selectively adding nitrogen to the inert gas as a sputtering gas. Filmed. Therefore, by forming the prevention layer 15 before the absorption layer 14 comes into contact with a gas such as oxygen, it is possible to prevent the absorption layer 14 from being brought into contact with oxygen or the like, thereby preventing defects from being generated on the surface of the absorption layer 14. This can be suppressed.

  Therefore, when producing the reflective mask 20 (see FIG. 5) using the reflective mask blank 10A, it is possible to suppress the occurrence of defects in the reflective mask 20 (see FIG. 5). Therefore, if the reflective mask blank 10A is used, a pattern having no defect can be formed stably.

  In the reflective mask blank 10A, the prevention layer 15 can be formed including at least one element of Ta, Ru, Cr, or Si. These elements are easy to dry-etch and have excellent cleaning resistance. Therefore, if the prevention layer 15 is configured to include Ta or the like, even if the absorption layer 14 includes Sn, the oxidation of the surface of the absorption layer 14 is prevented, and the absorber pattern 141 having strong cleaning resistance (see FIG. 5). ) Can be formed.

  In the reflective mask blank 10A, the prevention layer 15 is made of Ta alone, Ru alone, Cr alone, Si alone, Ta nitride, Ru nitride, Cr nitride, Si nitride, Ta boride, Ru. , Boride of Cr, boride of Si, or boron nitride of Ta. Since these simple substance, nitride, boride and boron nitride are amorphous, edge roughness of the absorber pattern 141 (see FIG. 5) can be suppressed. Therefore, if the prevention layer 15 is configured to include a nitride of Ta or the like, a highly accurate absorber pattern 141 (see FIG. 5) can be formed while preventing the surface of the absorption layer 14 including Sn from being oxidized.

  The reflective mask blank 10A can be formed by including at least one element of He, Ne, Ar, Kr or Xe in the prevention layer 15. When these elements are used as a sputtering gas at the time of forming the prevention layer 15, a small amount of these elements may be contained in the prevention layer 15 in some cases. Even in this case, the function of the prevention layer 15 can be exhibited without affecting the properties of the prevention layer 15.

  In the reflective mask blank 10A, the thickness of the prevention layer 15 can be set to 10 nm or less. Thereby, since the thickness of the prevention layer 15 can be suppressed, the reflective mask blank 10A has the entire thickness of the absorber pattern 141 (see FIG. 5) and the pattern of the prevention layer 15 formed thereon. Can be suppressed.

  In the reflective mask blank 10A, the absorbing layer 14 can be configured to include one or more elements selected from the group consisting of Ta, Cr, and Ti. Since these elements are contained in the absorption layer 14, the cleaning resistance of the absorption layer 14 can be further increased, and thus the absorption layer 14 can be made thinner. As a result, it is possible to obtain the absorption layer 14 having a high EUV light absorption rate even if it is thin. Therefore, the EUV light reflectance at the absorption layer 14 can be reduced while reducing the thickness of the reflective mask blank 10A and the thickness of the pattern of the reflective mask 20 (see FIG. 5).

  In the reflective mask blank 10A, the protective layer 13 is preferably provided between the reflective layer 12 and the absorbing layer 14. Thereby, when manufacturing the reflective mask 20 (see FIG. 5), the reflective layer 12 can be protected when etching the absorbing layer 14 or cleaning the reflective mask blank. Therefore, the reflectance of the obtained reflective mask 20 (see FIG. 5) with respect to EUV light can be improved.

<Method of manufacturing reflective mask blank>
Next, a method for manufacturing the reflective mask blank 10A shown in FIG. 1 will be described. FIG. 2 is a flowchart illustrating an example of a method for manufacturing the reflective mask blank 10A.

  As shown in FIG. 2, the reflective layer 12 is formed on the substrate 11 (a process of forming the reflective layer 12: step S11). The reflective layer 12 is formed on the substrate 11 by using a known film forming method so as to have a desired film thickness as described above.

  Next, a protective layer 13 is formed on the reflective layer 12 (a process of forming the protective layer 13: step S12). The protective layer 13 is formed on the reflective layer 12 by a known film forming method so as to have a desired thickness.

  Next, the absorbing layer 14 is formed on the protective layer 13 (a process of forming the absorbing layer 14: Step S13). The absorption layer 14 is formed on the protective layer 13 to a desired thickness by using a known film formation method. For example, the absorption layer 14 can be formed in a deposition chamber of a deposition apparatus using a known deposition apparatus.

  After the absorption layer 14 is formed, the storage chamber is taken out of the deposition chamber of the deposition apparatus used to form the absorption layer 14 and transferred to the storage chamber. It may be stored until used, such as until the layer 15 is formed.

  Next, the prevention layer 15 is formed on the absorption layer 14 (a step of forming the prevention layer 15: step S14). The prevention layer 15 has a desired film thickness on the absorption layer 14 in an inert gas atmosphere or a gas atmosphere in which nitrogen is selectively added to an inert gas by using a known film formation method. The film is formed as follows.

  Thereby, a reflective mask blank 10A as shown in FIG. 1 is obtained.

  In the present embodiment, in the method for manufacturing the reflective mask blank 10A, the step of forming the absorbing layer 14 (Step S13) and the step of forming the prevention layer 15 (Step S14) can be performed continuously. In this case, a binary sputtering method using a target such as a metal constituting the absorption layer 14 such as a Sn target and a target such as a metal constituting the prevention layer 15 such as a Ta target can be used. By using a binary sputtering method, charging of a target such as a metal forming the absorption layer 14 is completed earlier than charging of a target such as a metal forming the layer 15, so that the target can be formed in a film forming chamber of a film forming apparatus. The formation of the absorption layer 14 and the formation of the prevention layer 15 can be performed continuously.

(Other layers)
The reflection type mask blank 10A can include a hard mask layer 17 on the prevention layer 15 as shown in FIG. As the hard mask layer 17, a material having high resistance to etching, such as a Cr-based film, a Si-based film, and a Ru-based film, is used.

  Examples of the Cr-based film include Cr alone and a material obtained by adding O or N to Cr. Specifically, CrO, CrN, CrON and the like can be mentioned.

Examples of the Si-based film include Si alone and a material obtained by adding one or more kinds selected from the group consisting of O, N, C, and H to Si. Specifically, examples include SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON. Among them, the Si-based film is preferable because the side wall hardly recedes when the absorption layer 14 is dry-etched.

  Examples of the Ru-based film include Ru and a material obtained by adding O or N to Ru. Specifically, RuO, RuN, RuON and the like can be mentioned.

  By forming the hard mask layer 17 on the prevention layer 15, even if the minimum line width of the absorber pattern 141 is reduced, dry etching can be performed. Therefore, it is effective for miniaturization of the absorber pattern 141. When another layer is laminated on the prevention layer 15, the hard mask layer 17 may be provided on the outermost layer of the prevention layer 15.

  As shown in FIG. 4, the reflective mask blank 10A may include a back surface conductive layer 18 for electrostatic chuck on the second main surface 11b of the substrate 11 opposite to the side on which the reflective layer 12 is laminated. it can. The back conductive layer 18 is required to have a low sheet resistance as a characteristic. The sheet resistance value of the back surface conductive layer 18 is, for example, 250Ω / □ or less, and preferably 200Ω / □ or less.

  As a material including the back surface conductive layer 18, for example, a metal such as Cr or Ta or an alloy thereof can be used. As the alloy containing Cr, a Cr compound containing Cr and at least one selected from the group consisting of B, N, O, and C can be used. Examples of the Cr compound include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. As the alloy containing Ta, a Ta compound containing one or more selected from the group consisting of B, N, O, and C can be used. Examples of Ta compounds include, for example, TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiN, and TaSiON. .

  The thickness of the back surface conductive layer 18 is not particularly limited as long as it satisfies the function for an electrostatic chuck, but is, for example, 10 to 400 nm. The back conductive layer 18 can also be provided with a stress adjustment on the second principal surface 11b side of the reflective mask blank 10A. That is, the back conductive layer 18 can be adjusted so as to flatten the reflective mask blank 10A by balancing the stress from the various layers formed on the first main surface 11a side.

  As a method for forming the back surface conductive layer 18, a known film forming method such as a magnetron sputtering method or an ion beam sputtering method can be used.

  The back surface conductive layer 18 can be formed on the second main surface 11b of the substrate 11 before forming the protective layer 13, for example.

<Reflective mask>
Next, a reflective mask obtained by using the reflective mask blank 10A shown in FIG. 1 will be described. FIG. 5 is a schematic cross-sectional view showing an example of the configuration of the reflection type mask. As shown in FIG. 5, the reflective mask 20 is obtained by forming a desired absorber pattern 141 on the absorbing layer 14 of the reflective mask blank 10A shown in FIG.

  An example of a method for manufacturing the reflective mask 20 will be described. FIG. 6 is a diagram for explaining a manufacturing process of the reflective mask 20. As shown in FIG. 6A, a resist layer 19 is formed on the absorption layer 14 of the above-described reflective mask blank 10A shown in FIG.

  After that, a desired pattern is exposed on the resist layer 19. After the exposure, the exposed portion of the resist layer 19 is developed and washed (rinsed) with pure water to form a predetermined resist pattern 191 on the resist layer 19 as shown in FIG.

  Thereafter, the absorbing layer 14 is dry-etched using the resist layer 19 on which the resist pattern 191 is formed as a mask. Thus, as shown in FIG. 6C, an absorber pattern 141 corresponding to the resist pattern 191 is formed on the absorber layer 14.

As the etching gas, an F-based gas, a Cl-based gas, or a mixed gas containing a predetermined ratio of O ₂ , He, or Ar and the like can be used.

  Thereafter, the resist layer 19 is removed with a resist stripper or the like, and a desired absorber pattern 141 is formed on the absorber layer 14. Thereby, as shown in FIG. 5, it is possible to obtain the reflection type mask 20 in which the desired absorber pattern 141 is formed on the absorption layer 14.

  The obtained reflective mask 20 is irradiated with EUV light from the illumination optical system of the exposure apparatus. The EUV light that has entered the reflective mask 20 is reflected at a portion without the absorption layer 14 (the portion of the absorber pattern 141) and is absorbed at a portion with the absorption layer 14. As a result, the reflected light of the EUV light reflected by the absorption layer 14 passes through the reduction projection optical system of the exposure apparatus and irradiates an exposure material (for example, a wafer). Thereby, the absorber pattern 141 of the absorption layer 14 is transferred onto the exposure material, and a circuit pattern is formed on the exposure material.

[Second embodiment]
A reflective mask blank according to a second embodiment will be described with reference to the drawings. Note that members having the same functions as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 7 is a schematic sectional view of a reflective mask blank according to the second embodiment. As shown in FIG. 7, the reflective mask blank 10B has a stable layer 21 on the prevention layer 15 of the reflective mask blank 10A shown in FIG. That is, the reflective mask blank 10B is configured by laminating the substrate 11, the reflective layer 12, the protective layer 13, the absorption layer 14, the prevention layer 15, and the stable layer 21 in this order from the substrate 11 side.

As the stable layer 21, an oxide containing Ta, an oxynitride, and an acid boride can be used. Oxide containing Ta, as the oxynitride and acid borides, _e.g., include _{TaO, Ta 2 O 5, TaON} , TaCON, TaBO, TaBON, TaBCON, TaHfO, TaHfON, TaHfCON, TaSiO, a TaSiON and TaSiCON etc. Can be.

  The thickness of the stable layer 21 is preferably 10 nm or less. The thickness of the stable layer 21 is more preferably 7 nm or less, still more preferably 6 nm or less, further preferably 5 nm or less, and particularly preferably 4 nm or less. The thickness of the stable layer 21 is more preferably 1 nm or more, further preferably 2 nm or more, and particularly preferably 3 nm or more.

  The stable layer 21 can be formed by using a known film forming method such as a magnetron sputtering method or an ion beam sputtering method.

  As described above, the reflective mask blank 10B has the stable layer 21 on the prevention layer 15, so that the washing resistance of the prevention layer 15 can be further improved. By having the stable layer 21, a strong and stable film can be formed with good reproducibility, and the characteristics of the reflective mask blank and the reflective mask can be stabilized.

  Since the reflective mask blank 10B has the prevention layer 15 on the absorption layer 14 containing Sn, the surface of the absorption layer 14 is exposed to oxygen when forming the stable layer 21 on the prevention layer 15. Never. For example, when the stable layer 21 is formed using a reactive sputtering method, as described above, a mixed gas obtained by mixing oxygen with an inert gas such as He, Ar, or Kr, or nitrogen as an inert gas is used as a sputtering gas. And a mixed gas further mixed with oxygen is used. Since the prevention layer 15 is formed on the absorption layer 14, the surface of the absorption layer 14 does not come into contact with the mixed gas that is the sputtering gas when forming the stable layer 21. Therefore, the surface of the absorption layer 14 is not oxidized, and generation of precipitates on the surface of the absorption layer 14 can be prevented.

  In the reflective mask blank 10B, since the stable layer 21 is formed using an oxide, an oxynitride, or an oxyboride containing Ta, the composition in the stable layer 21 does not change due to cleaning, and therefore, the reflective layer 10B has higher resistance. A reflective mask blank and a reflective mask having excellent cleaning properties can be obtained.

  In the reflective mask blank 10B, by setting the film thickness of the stabilizing layer 21 to 10 nm or less, the thickness of the reflective mask blank 10B and the pattern of the reflective mask can be reduced, and the washing resistance of the prevention layer 15 can be improved. Can be maintained.

  Note that, as shown in FIG. 8, the reflective mask blank 10B may include the hard mask layer 17 on the stable layer 21, similarly to the reflective mask blank 10A according to the first embodiment shown in FIG. .

  Example 1 is a comparative example, and Examples 2 to 4 are Examples.

[Example 1]
FIG. 9 shows a reflective mask blank 100. The reflective mask blank 100 is different from the reflective mask blank 10A according to the first embodiment shown in FIG. 1 in that the reflective mask blank 100 does not have the prevention layer 15 on the absorbing layer 14.
(Preparation of reflective mask blank)
As the substrate for film formation, a SiO ₂ —TiO ₂ glass substrate (approximately 152 mm square and approximately 6.3 mm in thickness) was used. The thermal expansion coefficient of the glass substrate was 0.02 × 10 ⁻⁷ / ° C. or less. The glass substrate was polished to form a smooth surface having a surface roughness of 0.15 nm or less in root mean square roughness Rq and a flatness of 100 nm or less. On the back surface of the glass substrate, a Cr layer having a thickness of about 100 nm was formed using a magnetron sputtering method to form a back conductive layer (conductive film) for an electrostatic chuck. The sheet resistance of the Cr layer was about 100Ω / □. After fixing the glass substrate using the Cr film, the Si film and the Mo film were alternately formed on the surface of the glass substrate by ion beam sputtering for 40 cycles. The thickness of the Si film was about 4.5 nm, and the thickness of the Mo film was about 2.3 nm. Thus, a reflective layer (multilayer reflective film) having a total thickness of about 272 nm ((Si film: 4.5 nm + Mo film: 2.3 nm) × 40) was formed. Thereafter, a Ru layer (having a thickness of about 2.5 nm) was formed on the reflective layer by using an ion beam sputtering method to form a protective layer (protective film). Next, a 40 nm-thick absorbing layer (absorber film) made of a Sn-Ta alloy was formed on the protective layer by a magnetron sputtering method. Ar gas was used as a sputtering gas. The target used for sputtering had Sn of 60 at% and Ta of 40 at%, but the Ta content in the sputtered absorbing layer was 48 at%. In addition, the Sn content and the Ta content in the absorption layer were measured using X-ray fluorescence analysis (XRF) (Delta, manufactured by Olympus Corporation). Thus, a reflective mask blank 100 shown in FIG. 9 was produced. The thickness of the absorption layer was measured by XRR using an X-ray diffractometer (manufactured by Rigaku Corporation, SmartLab HTP). In addition, from the result of X-ray diffraction (XRD) measurement using the same apparatus, it was confirmed that the absorption layer made of the Sn-Ta alloy was amorphous.

(Observation of the surface of a reflective mask blank)
The surface of the reflective mask blank 100 was observed using a scanning electron microscope (Ultra 60, manufactured by Carl Zeiss). FIG. 10 shows the observation result of the surface of the reflective mask blank. As shown in FIG. 10, fine particles were observed on the surface of the reflective mask blank. As a result of analyzing the fine particles by energy dispersive X-ray analysis (EDX), it was confirmed that the fine particles were formed of tin oxide. It is considered that the fine particles on the surface of the absorption layer were generated when Sn contained in the absorption layer reacted with oxygen in the atmosphere when the absorption layer was exposed to the atmosphere. Such fine particles are not preferable because they may remain as pattern defects on the reflective mask after the etching of the absorption layer.

[Example 2]
In this example, a 4 nm thick TaN film serving as a prevention layer was formed on the absorption layer of the reflective mask blank 100 produced in Example 1 to produce the reflective mask blank 10A shown in FIG. Note that, for the prevention layer, a mixed gas of Ar and nitrogen was used as a sputtering gas using a reactive sputtering method, and the flow rate of Ar was 70 sccm and the flow rate of nitrogen was 2 sccm. The reflective mask blank 100 manufactured in Example 1 was transferred from the film forming chamber of the film forming apparatus used for forming the absorption layer to the storage room until the prevention layer was formed on the absorption layer. Was stored under high vacuum.

(Observation of the surface of a reflective mask blank)
The surface of the reflective mask blank 10A was observed using a scanning electron microscope. FIG. 11 shows the observation results of the surface of the absorption layer of the reflective mask blank 10A. As shown in FIG. 11, no fine particles were generated on the surface of the absorption layer of the reflective mask blank 10A. This is because oxygen in the atmosphere does not come into contact with Sn contained in the absorption layer because the prevention layer exists on the surface of the absorption layer.

[Example 3]
In this example, an anti-Ta layer was formed to a thickness of 2 nm by magnetron sputtering on the absorption layer of the reflective mask blank 100 produced in Example 1, and a TaO stable layer was further formed on the anti-Ta layer. A 2 nm film was formed using a reactive sputtering method. Thus, the reflective mask blank 10B shown in FIG. 7 was manufactured. When forming the prevention layer by the magnetron sputtering method, Ar gas was used as a sputtering gas. When the stable layer was formed by reactive sputtering, a mixed gas of Ar and oxygen was used as a sputtering gas, and the flow rate of Ar was 40 sccm and the flow rate of oxygen was 30 sccm. The reflective mask blank 100 manufactured in Example 1 was transferred from the film forming chamber of the film forming apparatus used for forming the absorption layer to the storage room until the prevention layer was formed on the absorption layer. Was stored under high vacuum.

  When the prevention layer and the stable layer of the reflective mask blank 10B after film formation were measured by XRR, the thickness of Ta was 0.9 nm and the thickness of TaO was 4.6 nm. This is considered to be because when the TaO film was formed on the Ta film, oxygen contained in the sputtering gas and Ta of the Ta film reacted to form a TaO film and expanded.

  Thereafter, the reflective mask blank 10B shown in FIG. 7 was dry-etched using a dry etching apparatus. In the dry etching, after the prevention layer and the stable layer were removed using an F-based gas, the absorption layer was removed using a Cl-based gas.

(Observation of the surface of a reflective mask blank)
The surface of the reflective mask blank 10B was observed using a scanning electron microscope. FIG. 12 shows the results of observation of the absorption layer on the surface of the reflective mask blank 10B. As shown in FIG. 12, deposits such as fine particles were not observed on the surface of the reflective mask blank. In this example, when forming the prevention layer, only Ar is used as a sputtering gas. Therefore, since the surface of the absorption layer is not exposed to an atmosphere containing oxygen, Sn present on the surface of the absorption layer does not react with oxygen. Thereby, it can be said that generation of precipitates on the surface of the absorption layer was suppressed.

[Example 4]
(Preparation of reflective mask blank)
In this example, in Example 3, when forming an absorption layer made of a Sn—Ta alloy, a binary sputtering method using a Sn target and a Ta target simultaneously instead of the Sn—Ta alloy target was used. Ar gas was used as a sputtering gas, the flow rate of Ar was set to 70 sccm, the input power to the Sn target was set to 130 W, and the input power to the Ta target was set to 200 W. When binary sputtering was performed, charging of the Sn target and the Ta target started simultaneously. The end time of charging the Sn target and the Ta target was set to 520 seconds after the start of charging for the Sn target, and to 608 seconds after the start of charging for the Ta target. Thus, a 35 nm-thick absorbing layer made of a Sn—Ta alloy and a 2 nm-thick preventing layer made of Ta were continuously formed on the absorbing layer by one sputtering. Thereafter, a stable layer made of TaO was formed to a thickness of 2 nm on the prevention layer by using a reactive sputtering method as in Example 3. Thus, the reflective mask blank 10B shown in FIG. 7 was manufactured. The Ta content in the sputtered absorption layer was measured using XRF, and was found to be 35%.

(Observation of the surface of a reflective mask blank)
When the surface of the reflective mask blank 10B produced in this example was observed using a scanning electron microscope, no deposits such as fine particles were observed on the surface of the reflective mask blank 10B. When the absorption layer and the prevention layer are formed by two times of sputtering as in Example 2 or 3, the reflective mask blank 100 produced by forming the absorption layer in Example 1 is used for forming the absorption layer. It is necessary to return to the storage room from the film forming chamber of the film forming apparatus that was used. Although the storage chamber is kept in a high vacuum, there is a risk that fine particles of oxide may be generated on the surface of the absorbing film due to a slight amount of residual oxygen. In this example, since the absorption layer and the prevention layer are continuously formed in the film forming chamber of the film forming apparatus to produce the reflective mask blank 10B, generation of oxide fine particles in the storage room is performed. Can be reduced. Further, since only one sputtering is required, the manufacturing time of the reflective mask blank 10B can be reduced.

  As described above, the embodiment has been described. However, the above embodiment is presented as an example, and the present invention is not limited by the above embodiment. The above embodiment can be implemented in other various forms, and various combinations, omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

  This application claims priority based on Japanese Patent Application No. 2018-112601 filed with the Japan Patent Office on June 12, 2018, and incorporates the entire contents of Japanese Patent Application No. 2018-112601 into this application. .

10A, 10B Reflective mask blank 11 Substrate 12 Reflective layer 13 Protective layer 14 Absorbing layer 15 Preventive layer 17 Hard mask layer 18 Back conductive layer 19 Resist layer 20 Reflective mask 21 Stable layer

Claims (15)

A reflective mask blank having, on a substrate, a reflective layer that reflects EUV light and an absorbing layer that absorbs EUV light in this order from the substrate side,
The absorption layer contains Sn,
A reflective mask blank having a protective layer on the absorbing layer for preventing oxidation of the absorbing layer.   The reflective mask blank according to claim 1, wherein the prevention layer contains one or more elements selected from the group consisting of Ta, Ru, Cr, Ti, and Si, and does not contain Sn and oxygen.   The prevention layer is composed of Ta alone, Ru alone, Cr alone, Ti alone, Si alone, nitride of Ta, nitride of Ru, nitride of Cr, nitride of Ti, nitride of Si, boride of Ta, 3. The reflective mask blank according to claim 2, comprising at least one component selected from the group consisting of a boride of Ru, a boride of Cr, a boride of Ti, a boride of Si, and a boron nitride of Ta. .   The reflective mask blank according to any one of claims 1 to 3, wherein the prevention layer includes one or more elements selected from the group consisting of He, Ne, Ar, Kr, and Xe.   The reflective mask blank according to claim 1, wherein the thickness of the prevention layer is 10 nm or less.   The reflective mask blank according to any one of claims 1 to 5, wherein the absorption layer contains at least one element selected from the group consisting of Ta, Cr, and Ti.   The reflective mask blank according to any one of claims 1 to 6, further comprising a stable layer on the prevention layer.   The reflective mask blank according to claim 7, wherein the stable layer contains at least one selected from the group consisting of an oxide containing Ta, an oxynitride, and an oxyboride.   9. The reflective mask blank according to claim 7, wherein the thickness of the stable layer is 10 nm or less.   The reflective mask blank according to any one of claims 1 to 9, further comprising a protective layer between the reflective layer and the absorbing layer.   The reflective mask blank according to claim 1, further comprising a hard mask layer on the prevention layer or on a layer on the outermost surface side of the prevention layer.   The reflective mask blank according to claim 11, wherein the hard mask layer includes at least one element selected from the group consisting of Cr, Si, and Ru.   A reflective mask in which a pattern is formed on the absorption layer of the reflective mask blank according to claim 1. A method of manufacturing a reflective mask blank having a reflective layer that reflects EUV light and an absorbing layer that absorbs EUV light on a substrate in this order from the substrate side,
Forming the reflective layer on the substrate;
Forming the absorption layer containing Sn on the reflection layer;
Forming a prevention layer on the absorption layer to prevent oxidation of the absorption layer;
A method for producing a reflective mask blank comprising:   The reflection type according to claim 14, wherein the step of forming the absorption layer and the step of forming the prevention layer are continuously performed in a film forming chamber by using a binary sputtering method. Manufacturing method of mask blank.