TW202000954A - Reflective mask blank, reflective mask, and method of manufacturing reflective mask blank - Google Patents

Abstract

A reflective mask blank has a reflective layer to reflect EUV light and an absorber layer to absorb the EUV light, formed over a substrate in this order from a substrate side. The absorber layer contains Sn, and a preventive layer is provided over the absorber layer, to prevent oxidation of the absorber layer.

Description

Reflective mask base, reflective mask and method for manufacturing reflective mask base

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

In recent years, with the miniaturization of integrated circuits constituting semiconductor devices, as an exposure method that replaces previous exposure technologies using visible light, ultraviolet light (wavelength 193-365 nm) or ArF excimer laser light (wavelength 193 nm), etc., The ultra-violet (Etreme Ultra Violet: hereinafter referred to as "EUV") lithography method is being studied.

In EUV lithography, EUV light with a shorter wavelength than ArF excimer laser light is used as the light source for exposure. In addition, EUV light refers to light of a wavelength in the soft X-ray region or vacuum ultraviolet region, 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.

Because EUV light is easily absorbed by all substances, it is impossible to use the refractive optical system used in the previous exposure technology. Therefore, in the EUV lithography method, a reflective optical system such as a reflective mask or a mirror surface is used. In the EUV lithography method, a reflective mask is used as a mask for transfer.

In the reflective mask, a reflective layer that reflects EUV light is formed on the substrate, and an absorption layer that absorbs EUV light is formed in a pattern on the reflective layer. The reflective reticle is formed by depositing a reflective layer and an absorption layer on the substrate in order from the substrate side as the original plate, removing a part of the absorption layer to form a specific pattern, and then cleaning with a cleaning solution. obtain.

The 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 the exposed material (resist coated wafer) by an optical system. By this, the pattern of the absorption layer is transferred to the surface of the exposed material.

In the EUV lithography method, EUV light is generally incident on the reflective mask from a direction inclined by about 6°, and is similarly reflected obliquely. Therefore, if the film thickness of the absorption layer is thick, it may block the optical path of the EUV light (shadowing). Due to the influence of shadowing, if a portion that becomes a shadow of the absorption layer is generated on the substrate or the like, the pattern of the reflective mask may not be faithfully transferred on the surface of the exposed material, and the pattern accuracy is deteriorated. On the other hand, if the film thickness of the absorption layer is made thin, the light shielding performance of EUV light of the reflective mask will decrease and the reflectance of EUV light will increase, so the contrast between the pattern part of the reflective mask and the other parts May be reduced.

Here, research is conducted on a reflective mask substrate that suppresses the decrease in contrast while faithfully transferring the pattern of the reflective mask. For example, Patent Literature 1 describes a reflective reticle base that constitutes an absorber film made of a material that contains Ta as a main component and contains 50 atomic% (at%) or more, and further includes a group selected from Te, Sb, and Pt. At least one element of I, Bi, Ir, Os, W, Re, Sn, In, Po, Fe, Au, Hg, Ga, and Al.

However, in the reflective reticle substrate described in Patent Document 1, the surface of the absorber film may be oxidized to generate fine particles on the surface of the absorber film, thereby causing defects 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 producing a reflective mask, if there are particles in the portion where the absorber film should be scraped by dry etching, this portion may not be etched and become a pattern defect in which the absorber film remains. In this case, when the wafer is exposed, the pattern defects on the reflective mask are transferred to the exposure material (resist) applied to the wafer, which is not good. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-273678

[Problems to be solved by the invention]

An object of one aspect of the present invention is to provide a reflective mask base capable of suppressing surface oxidation of an absorption layer and generating defects on the surface of the absorption layer. [Technical means to solve the problem]

One aspect of the reflective mask base of the present invention is a reflective mask base having a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light on the substrate in order from the substrate side, the absorber layer contains Sn, The absorption layer is provided with a prevention layer to prevent the oxidation of the absorption layer. [Effect of invention]

According to one aspect of the present invention, a reflective mask base capable of suppressing oxidation of the surface of the absorption layer and generating defects on the surface of the absorption layer can be provided.

Hereinafter, embodiments of the present invention will be described in detail. In addition, in order to facilitate understanding of the description, the same constituent elements in each figure are denoted by the same symbol, and repeated description is omitted. In addition, the scale of each component in the figure is sometimes different from the actual one. In this manual, a 3-axis orthogonal coordinate system in the three-axis direction (X-axis direction, Y-axis direction, Z-axis direction) is used, the coordinates of the main surface of the substrate are set to the X-axis direction and the Y-axis direction, and the height direction (thickness direction) ) Is set to the Z axis direction. The upward direction from below the substrate (the direction from the main surface of the substrate to the reflective layer) is set to the +Z axis direction, and the opposite direction is set to the -Z axis direction. In the following description, the +Z axis direction is sometimes referred to as up, and the -Z axis direction is referred to as down. In this specification, unless otherwise specified, the wavy line "~" indicating the numerical range means including the numerical values described before and after it as the lower limit and upper limit.

<Reflective Mask Base> The reflective mask base of the first embodiment will be described. FIG. 1 is a schematic cross-sectional view of a reflective mask base of the first embodiment. As shown in FIG. 1, the reflective mask base 10A is formed by sequentially stacking a reflective layer 12, a protective layer 13, an absorption layer 14, and a prevention layer 15 on a substrate 11.

(Substrate) The substrate 11 preferably has a small thermal expansion coefficient. When the thermal expansion coefficient of the substrate 11 is small, it is possible to suppress the deformation of the pattern formed in the absorption layer 14 due to the heat of EUV light during exposure. 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 thermal expansion coefficient, for example, SiO ₂ -TiO ₂ glass can be used. For the SiO ₂ -TiO ₂ glass, it is preferable to use quartz glass containing 90% by mass to 95% by mass of SiO ₂ and 5% by mass to 10% by mass of TiO ₂ . If the content of TiO ₂ is 5% by mass to 10% by mass, the linear expansion coefficient near room temperature is approximately zero, and there is almost no dimensional change near room temperature. Furthermore, the SiO ₂ -TiO ₂ glass may also contain trace components other than SiO ₂ and TiO ₂ .

The first main surface 11a of the substrate 11 on the side where the reflective layer 12 is deposited preferably has high smoothness. The smoothness of the first principal surface 11a can be evaluated by the surface roughness measured by atomic force microscopy. The surface roughness of the first principal surface 11a is preferably 0.15 nm or less in terms of root mean square roughness Rq.

The first main surface 11a is preferably surface-processed so as to have a specific flatness. The reason is that the reflective mask obtains higher pattern transfer accuracy and position accuracy. In the specific area of the first main surface 11a (for example, the area of 132 mm×132 mm), the flatness of the substrate 11 is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 30 nm or less.

In addition, the substrate 11 is preferably resistant to the cleaning liquid used in the cleaning of the reflective mask base, the patterned reflective mask base or the reflective mask, and the like.

Furthermore, the substrate 11 preferably has a high hardness in order to prevent deformation caused by the film stress of the film (reflecting layer 12 etc.) formed on the substrate 11. For example, the substrate 11 preferably has a high Young's modulus of 65 GPa or more.

The size or thickness of the substrate 11 is appropriately determined according to the design value 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 term “rectangular” includes, in addition to a rectangle or a square, a shape in which arcs are formed at the corners of the rectangle or the square.

(Reflection layer) The reflection layer 12 has a high reflectivity for EUV light. Specifically, when EUV light is incident on the surface of the reflective layer 12 at an incident angle of 6°, the maximum reflectance of EUV light near a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% or more. In addition, when the protective layer 13 and the absorption layer 14 are stacked on the reflective layer 12, similarly, the maximum reflectance of EUV light at a wavelength of around 13.5 nm is preferably 60% or more, and more preferably 65% the above.

The reflective layer 12 is a multilayer film in which a plurality of layers with elements having different refractive indexes as main components are periodically stacked. The reflective layer 12 is generally a multilayer reflective film formed by alternately stacking a plurality of high-refractive-index layers showing high refractive index for EUV light and low-refractive-index layers showing low refractive index for EUV light from the substrate 11 side.

The multilayer reflective film can use the layered structure in which the high-refractive-index layer and the low-refractive-index layer are sequentially stacked from the substrate 11 side as one cycle and a plurality of cycles, or the layered structure in which the low-refractive-index layer and the high-refractive-index layer are sequentially stacked Multiple cycles are accumulated as 1 cycle. Furthermore, in this case, the multilayer reflective film preferably has the topmost layer (uppermost layer) as a high refractive index layer. The reason is that since the low refractive index layer is easily oxidized, if the low refractive index layer becomes the uppermost layer of the reflective layer 12, the reflectance 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, in addition to Si alone, Si can be used to contain one or more Si compounds selected from the group consisting of B, C, N, and O. By using a high-refractive-index layer containing Si, a reflective mask excellent in EUV light reflectance is obtained. As the low refractive index layer, a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or alloys of these can be used. In this embodiment, it is preferable that the low-refractive-index layer includes a layer of Mo and the high-refractive-index layer includes a layer of Si. Furthermore, in this case, by setting the uppermost layer of the reflective layer 12 as a high refractive index layer (layer containing Si), a layer containing Si and O is formed between the uppermost layer (layer containing Si) and the protective layer 13 The silicon oxide layer improves the cleaning resistance of the reflective mask.

The reflective layer 12 includes a plurality of high-refractive-index layers and low-refractive-index layers, but the film thicknesses of the high-refractive-index layers and the low-refractive-index layers may not be the same.

The film thickness and period of each layer constituting the reflective layer 12 can be appropriately selected according to the film material used, the reflectance of EUV light required by the reflective layer 12, or the wavelength (exposure wavelength) of EUV light. For example, when the reflective layer 12 sets the maximum value of the reflectance of EUV light at a wavelength near 13.5 nm to 60% or more, it is preferable to use a low refractive index layer (including Mo/Si multilayer reflective film made of high refractive index layer (including Si layer).

In addition, each layer constituting the reflective layer 12 can be formed by a known film forming method such as a magnetron sputtering method or an ion beam sputtering method so as to have a desired film thickness. For example, when the reflection layer 12 is formed by the ion beam sputtering method, it is performed by supplying ion particles to the target of the high refractive index material and the target of the low refractive index material from the ion source. In the case where the reflective layer 12 is a Mo/Si multilayer reflective film, by ion beam sputtering, for example, first, a Si target is used to form a layer containing Si with a specific film thickness on the substrate 11. Thereafter, using a Mo target, a layer containing Mo of a specific film thickness is formed. Taking the layer containing Si and the layer containing Mo as one cycle, and stacking it for 30 cycles to 60 cycles, a Mo/Si multilayer reflection film is formed.

(Protective layer) The protective layer 13 is etched (usually dry etching) on the absorber layer 14 to form an absorber pattern 141 on the absorber layer 14 during the manufacture of the reflective mask 20 (see FIG. 5) described below (refer to FIG. 5), the surface of the reflective layer 12 is suppressed from being damaged by etching, and the reflective layer 12 is protected. In addition, the resist layer 19 (see FIG. 6) remaining in the reflective mask base after etching is peeled off with a cleaning solution. When the reflective mask base is cleaned, the reflective layer 12 is protected from the cleaning solution. Therefore, the obtained reflective mask 20 (see FIG. 5) has good reflectivity to EUV light.

In FIG. 1, the case where the protective layer 13 is one layer is shown, but the protective layer 13 may be a plurality of layers.

As the material for forming the protective layer 13, when etching the absorption layer 14, a substance that is not easily damaged by etching is selected. As a substance that satisfies this condition, for example, Ru metal is a simple substance, and Ru contains one or more types selected from the group consisting of B, Si, Ti, Nb, Mo, Zr, Y, La, Co, and Re Ru-based materials such as Ru alloys of metals, nitrides containing nitrogen in Ru alloys; Cr, Al, Ta and nitrides containing nitrogen in these; SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ or the Etc. mixture. Among these, Ru metal element and Ru alloy, CrN and SiO _{2 are} preferable. The Ru metal element and the Ru alloy are not easy to be etched for a gas containing no oxygen, and are particularly good at functioning as an etching stop layer during processing of 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, it is possible to suppress the diffusion of Si from the Si layer of the reflective layer 12 to the protective layer 13. In addition, the protective layer 13 can sufficiently ensure the reflectance of EUV light on one side, and has a function as an etching stop layer when the absorption layer 14 is etched. Furthermore, it is possible to have the cleaning resistance of the reflective mask, and it is possible to 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 terms of maintaining the reflectivity of EUV light reflected by the reflective layer 12, the film thickness of the protective layer 13 is preferably 1 nm or more, more preferably 1.5 nm or more, and further preferably 2 nm or more. The film thickness of the protective layer 13 is preferably 8 nm or less, more preferably 6 nm or less, and further preferably 5 nm or less.

As a method of 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) The absorbing layer 14 needs to have the following characteristics in order to be used in the reflective mask of the EUV lithography method: the EUV light has a high absorption coefficient, can be easily etched, and has high cleaning resistance to the cleaning liquid.

The absorption layer 14 absorbs EUV light, and the reflectivity of EUV light is extremely low. Specifically, the maximum value of the reflectance of EUV light at a wavelength around 13.5 nm when EUV light is irradiated onto the surface of the absorption layer 14 is preferably 2% or less, and more preferably 1% or less. Therefore, the absorption layer 14 needs to have a high absorption coefficient of EUV light.

In addition, the absorption layer 14 is etched and processed 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 or CHF ₃ . Therefore, the absorption layer 14 needs to be able to be easily etched.

Furthermore, when the absorption layer 14 is manufactured in the following reflective mask 20 (see FIG. 5 ), when the resist pattern 191 (see FIG. 6) remaining in the etched reflective mask substrate is removed with a cleaning solution Exposure to cleaning fluid. At this time, as the cleaning liquid, sulfuric acid hydrogen peroxide mixture (SPM), sulfuric acid, ammonia, ammonia water hydrogen peroxide mixture (APM), OH radical cleaning water, ozone water and the like are used. In the EUV lithography method, SPM is generally used as a resist cleaning solution. Furthermore, SPM is a solution obtained by mixing sulfuric acid and hydrogen peroxide, for example, a solution obtained by mixing sulfuric acid and hydrogen peroxide in a volume ratio of 3:1. At this time, the temperature of SPM is preferably controlled at 100°C or higher in terms of increasing the etching rate. Therefore, the absorption layer 14 needs to improve the cleaning resistance to the cleaning liquid. The absorber layer 14 is preferably etched at 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 characteristics described above, the absorption layer 14 contains Sn. Since the absorption coefficient of Sn is large, the absorption layer 14 can reduce the reflectance of the absorption layer 14 by containing Sn. In addition, 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 contain one kind alone or two or more kinds. The absorber layer 14 further contains one or more of these elements in addition to Sn to improve cleaning resistance.

The absorption layer 14 may include N, B, Hf, or H in addition to Sn. These elements may contain one kind alone or two or more kinds. In particular, the absorption layer 14 preferably contains at least one of N or B among these elements. By including at least one of N or B, the absorption layer 14 can make the crystalline state of the absorption layer 14 into an amorphous or microcrystalline structure.

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

The absorption layer 14 is preferably amorphous in a crystalline state. Thereby, the absorption layer 14 can have excellent smoothness and flatness. In addition, by improving the smoothness and flatness of the absorber layer 14, the edge roughness of the absorber pattern 141 (see FIG. 5) becomes smaller, and the dimensional accuracy of the absorber pattern 141 (see FIG. 5) can be improved.

The absorption layer 14 may be a single-layer film or a multilayer film including a plurality of layers. When the absorption layer 14 is a single-layer film, the number of steps in manufacturing the mask base can be reduced to improve production efficiency. When the absorption layer 14 is a multilayer film, by appropriately setting the optical constant or film thickness of the layer on the upper side of the absorption layer 14, the layer on the upper side of the absorption layer 14 can be used to inspect the absorber pattern 141 using inspection light (Refer to Fig. 5) The anti-reflection film at the time. This can improve the inspection sensitivity when inspecting the absorber pattern.

The film thickness of the absorption layer 14 can be appropriately designed according to the composition of the absorption layer 14, etc., but it is preferably thin in terms of suppressing the influence of shadowing. The film thickness of the absorption layer 14 is preferably 40 nm or less in terms of obtaining sufficient contrast while maintaining the reflectance of the absorption layer 14 at 1% or less. The film thickness of the absorption 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 film thickness of the absorption 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, X-ray reflectance method (XRR) or TEM (Transmission Electron Microscopy).

The absorption layer 14 can be formed using a known film forming method such as a magnetron sputtering method or an ion beam sputtering method. For example, when the SnTa film is formed as the absorber layer 14 using a magnetron sputtering method, a target containing Sn and Ta is used, and the absorber layer 14 can be formed into a film by a sputtering method using Ar gas. In addition, the absorption layer 14 can also be formed into a film by a binary sputtering method using Sn targets and Ta targets at the same time.

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

As a material for forming the prevention layer 15, Ta, Ru, Cr, Ti, or Si can be used. These elements may contain one kind alone or two or more kinds.

For the prevention layer 15, Ta element, Ru element, Cr element, Ti element, Si element, Ta nitride, Ru nitride, Cr nitride, Ti nitride, Si nitride, Ta boride, Ru boride, Cr boride, Ti boride, Si boride or Ta boron nitride. These may include one kind alone or two or more kinds.

The preferred composition of the prevention layer 15 is, for example, Ta, TaN, TaB, or TaBN. For example, as described below, the reflective mask base 10B of the second embodiment having the stabilizing layer 21 formed on the prevention layer 15 (see FIG. 7 ). In addition, the stabilizing layer 21 includes an oxide, oxynitride, or boron oxide containing Ta. In this case, if the prevention layer 15 is made of such materials, the same target can be used when forming the prevention layer 15 and the stabilization layer 21 into a film. Therefore, the number of necessary film forming chambers and the like can be reduced, and the reflective mask base 10B (see FIG. 7) is excellent in productivity.

The prevention layer 15 may further contain elements such as He, Ne, Ar, Kr, or Xe.

The prevention layer 15 is a layer that does not contain Sn and oxygen. The absence of Sn and oxygen means that immediately after the formation of the prevention layer 15, Sn and oxygen are not present on the surface and inside of the prevention layer 15. If the prevention layer 15 is exposed to an environment containing oxygen, then on the surface where the prevention layer 15 is in contact with oxygen, by preventing the components contained in the layer 15 from reacting (oxidizing) with oxygen, there is the formation of oxides on the surface of the prevention layer 15 The situation of the membrane. At this time, if Sn is contained in the prevention layer 15, the Sn present on the surface of the layer 15 may be prevented from reacting with oxygen, and fine particles containing Sn, such as tin oxide, are generated as precipitates on the surface of the prevention layer 15, so the prevention layer 15 does not Contains Sn.

Furthermore, the prevention layer 15 does not contain oxygen means that in the step after the prevention layer 15 is formed into a film, when there is a film of an oxide formed on the surface of the prevention layer 15 in contact with oxygen, the oxide is not included Oxygen contained in the membrane. On the other hand, since the interface between the absorption layer 14 and the prevention layer 15 is not in 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 using a known film forming method such as magnetron sputtering or ion beam sputtering, in an inert gas environment, or in an inert gas atmosphere in which nitrogen is selectively added. For example, when the Ta film, the Ru film, the Cr film or the Si film are formed as the prevention layer 15 using the magnetron sputtering method, a target containing Ta, Ru, Cr or Si is used, and an inert gas such as He, Ar or Kr is used Or, a gas in which nitrogen is selectively added to the inert gas is used as the sputtering gas, whereby the film formation prevention layer 15 is formed.

Regarding the film thickness of the prevention layer 15, if the prevention layer 15 is too thick, the etching of the prevention layer 15 takes time. In addition, there is a possibility that the shading and the like become larger. On the other hand, if the prevention layer 15 is too thin, there is a possibility that the function as the prevention layer 15 cannot be stably and sufficiently exerted. Therefore, in terms of suppressing the thickness of the pattern of the reflective mask substrate 10A, the thickness of the prevention layer 15 may be about several nm, and preferably 10 nm or less. The film 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 film thickness of the prevention layer 15 is more preferably 0.5 nm or more, further preferably 1 nm or more, further preferably 1.5 nm or more, and particularly preferably 2 nm or more. The film thickness of the prevention layer 15 can be measured using, for example, XRR or TEM.

In this way, the reflective mask base 10A has the prevention layer 15 on the Sn-containing absorption layer 14. If the absorption layer 14 is in contact with oxygen, a part of Sn on the surface of the absorption layer 14 may react with oxygen, and Sn-containing fine particles composed of tin oxide or the like may be generated on the surface of the absorption layer 14 as precipitates. As described above, the prevention layer 15 is formed on the absorption layer 14 using only inert gas such as He, Ar, Kr, or a gas to which nitrogen is selectively added to the inert gas as a sputtering gas. 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 coming into contact with oxygen or the like. Thereby, it is possible to prevent the surface of the absorption layer 14 from being oxidized, and to produce precipitates on the surface of the absorption layer 14, and to suppress the occurrence of defects on the surface of the absorption layer 14.

Accordingly, when the reflective mask 20 (see FIG. 5) is manufactured using the reflective mask substrate 10A, it is possible to suppress the occurrence of defects in the reflective mask 20 (see FIG. 5 ). Therefore, if the reflective mask base 10A is used, a defect-free pattern can be stably formed.

The reflective mask substrate 10A may contain at least one element of Ta, Ru, Cr, or Si to form the prevention layer 15. These elements are easy to dry etch and have excellent cleaning resistance. In this way, if the prevention layer 15 is made of Ta or the like, even if the absorption layer 14 contains Sn, it is possible to prevent the oxidation of the surface of the absorption layer 14 and form an absorber pattern 141 with high cleaning resistance (see FIG. 5) .

The reflective mask substrate 10A uses Ta elemental substance, Ru elemental substance, Cr elemental substance, Si elemental substance, Ta nitride, Ru nitride, Cr nitride, Si nitride, Ta boride, Ru boride, Cr The boride, the boride of Si, or the boron nitride of Ta forms the prevention layer 15. Since these elements, nitride, boride, and boron nitride are amorphous, it is possible to suppress the edge roughness of the absorber pattern 141 (see FIG. 5). In this way, if the prevention layer 15 is composed of a nitride of Ta or the like, the oxidation of the surface of the absorption layer 14 containing Sn can be prevented, and a high-accuracy absorber pattern 141 can be formed (see FIG. 5 ).

The reflective mask base 10A may be formed in the prevention layer 15 including at least one element of He, Ne, Ar, Kr, or Xe. Since these elements are used as the sputtering gas during the film formation of the prevention layer 15, there are cases where these elements are contained in a small amount in the prevention layer 15. That is to facilitate this situation, the function of the prevention layer 15 can also be exerted without affecting the properties of the prevention layer 15.

In the reflective mask base 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 base 10A can suppress the overall thickness of the absorber pattern 141 (see FIG. 5) and the pattern of the prevention layer 15 formed thereon.

The reflective mask substrate 10A may include one or more elements selected from the group consisting of Ta, Cr, and Ti to constitute the absorption layer 14. By including these elements in the absorption layer 14, the cleaning resistance of the absorption layer 14 can be further improved, so the absorption layer 14 can be made thinner. As a result, a thin absorption layer 14 having a high absorption rate of EUV light can also be obtained. As a result, the thinning of the reflective mask base 10A and the thinning of the pattern of the reflective mask 20 (see FIG. 5) can be achieved, and the reflectance of the EUV light of the absorption layer 14 can be reduced.

The reflective mask base 10A preferably has the protective layer 13 disposed between the reflective layer 12 and the absorption layer 14. Thereby, the reflective layer 12 can be protected when the absorption layer 14 is etched or when the reflective mask base is cleaned during the manufacture of the reflective mask 20 (see FIG. 5 ). Therefore, the reflectivity of the obtained reflective mask 20 (see FIG. 5) to EUV light can be improved.

<Manufacturing method of reflective mask base> Next, a manufacturing method of the reflective mask base 10A shown in FIG. 1 will be described. FIG. 2 is a flowchart showing an example of a method of manufacturing the reflective mask substrate 10A.

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

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

Then, the absorber layer 14 is formed on the protective layer 13 (step of forming the absorber layer 14: step S13). The absorber layer 14 is formed on the protective layer 13 so as to have a desired film thickness using a known film forming method. For example, the absorber layer 14 can be formed in a film forming chamber of a film forming apparatus using a known film forming apparatus.

Furthermore, after the absorption layer 14 is formed, after being taken out from the film forming chamber of the film forming apparatus used in the formation of the absorption layer 14 and moved to the storage room, the storage room may be placed in a high vacuum state and stored until, for example, in the absorption layer The prevention layer 15 and the like are formed on the 14 until it is used.

Then, the prevention layer 15 is formed on the absorption layer 14 (the formation step of the prevention layer 15: step S14). The prevention layer 15 is formed on the absorption layer 14 in an inert gas atmosphere or a gas atmosphere in which nitrogen is selectively added to the inert gas atmosphere by a known film formation method.

Thereby, the reflective mask base 10A shown in FIG. 1 is obtained.

Moreover, in this embodiment, the manufacturing method of the reflective mask base 10A can continuously perform the step of forming the absorption layer 14 (step S13) and the step of forming the prevention layer 15 (step S14). In this case, a binary sputtering method using a target such as a metal such as a Sn target that constitutes the absorption layer 14 and a target such as a Ta target such as a metal that constitutes the prevention layer 15 can be used. Using the binary sputtering method, the charging of the target of the metal and the like constituting the absorption layer 14 is completed earlier than that of the target of the metal and the like constituting the prevention layer 15, whereby it can be continuously performed in the film forming chamber of the film forming apparatus The formation of the absorption layer 14 and the formation of the prevention layer 15.

(Other layers) As shown in FIG. 3, the reflective mask base 10A may include a hard mask layer 17 on the prevention layer 15. As the hard mask layer 17, a material having high etching resistance such as a Cr-based film, a Si-based film, and a Ru-based film is used.

As the Cr-based film, for example, a single element of Cr, a material in which O or N is added to Cr, and the like. Specifically, CrO, CrN, CrON, etc. may be mentioned.

Examples of the Si-based film include Si as a simple substance and one or more materials selected from the group consisting of O, N, C, and H added to Si. Specifically, SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, SiCON, etc. may be mentioned. Among them, the Si-based film is preferable because the side wall does not easily retreat when the absorption layer 14 is dry-etched.

Examples of the Ru-based film include Ru and materials in which O or N is added to Ru. Specifically, RuO, RuN, RuON, etc. may be mentioned.

Since the hard mask layer 17 is formed on the prevention layer 15, even if the minimum line width of the absorber pattern 141 becomes small, dry etching can be performed. Therefore, it is effective for miniaturization of the absorber pattern 141. In addition, in the case where other layers are stacked on the prevention layer 15, the hard mask layer 17 may be provided on the topmost layer of the prevention layer 15.

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

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

The film thickness of the back surface conductive layer 18 is not particularly limited as long as it functions as an electrostatic chuck, and it is, for example, 10 to 400 nm. In addition, the back conductive layer 18 may include a stress adjustment on the second principal surface 11b side of the reflective mask base 10A. That is, the back surface conductive layer 18 balances the stress from the various layers formed on the first main surface 11a side, and can be adjusted so that the reflective mask base 10A is flat.

The method for forming the back conductive layer 18 may use a known film forming method such as a magnetron sputtering method or an ion beam sputtering method.

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

<Reflective Mask> Next, the reflective mask obtained using the reflective mask base 10A shown in FIG. 1 described above will be described. 5 is a schematic cross-sectional view showing an example of the structure of a reflective mask. As shown in FIG. 5, the reflective mask 20 forms a desired absorber pattern 141 on the absorption layer 14 of the reflective mask substrate 10A shown in FIG. 1.

An example of the manufacturing method of the reflective mask 20 will be described. FIG. 6 is a diagram illustrating the manufacturing steps of the reflective mask 20. As shown in FIG. 6(a), a resist layer 19 is formed on the absorption layer 14 of the reflective mask base 10A shown in FIG. 1 described above.

Thereafter, the resist layer 19 is exposed to a desired pattern. After the exposure, the exposed portion of the resist layer 19 is developed and washed (rinsed) with pure water, thereby forming a specific resist pattern 191 on the resist layer 19 as shown in FIG. 6(b).

Thereafter, the resist layer 19 on which the resist pattern 191 is formed is used as a photomask, and the absorption layer 14 is dry-etched. As a result, as shown in FIG. 6( c ), the absorber pattern 141 corresponding to the resist pattern 191 is formed on the absorber layer 14.

As the etching gas, a mixed gas containing F-based gas, Cl-based gas, Cl-based gas and O ₂ , He, or Ar at a specific ratio can be used.

After that, the resist layer 19 is removed by a resist stripping solution or the like, and a desired absorber pattern 141 is formed on the absorber layer 14. Thereby, as shown in FIG. 5, the reflective mask 20 in which the required absorber pattern 141 is formed on the absorber layer 14 can be obtained.

The illumination optical system of the self-exposure device irradiates the obtained reflective mask 20 with EUV light. The EUV light incident on the reflective mask 20 is reflected at the portion without the absorption layer 14 (the portion of the absorber pattern 141), and is absorbed at the portion with the absorption layer 14. As a result, the reflected light of the EUV light reflected on the absorption layer 14 passes through the reduction projection optical system of the exposure device and is irradiated to the exposure material (eg, wafer, etc.). Thereby, the absorber pattern 141 of the absorber layer 14 is transferred onto the exposure material, and a circuit pattern is formed on the exposure material.

[Second Embodiment] The reflective mask base of the second embodiment will be described with reference to the drawings. In addition, members having the same functions as those in the above-mentioned embodiments are denoted by the same symbols, and detailed explanations are omitted.

7 is a schematic cross-sectional view of a reflective mask base in a second embodiment. As shown in FIG. 7, the reflective mask base 10B has a stabilizing layer 21 on the prevention layer 15 of the reflective mask base 10A shown in FIG. 1. That is, the reflective mask base 10B is formed by sequentially stacking the substrate 11, the reflective layer 12, the protective layer 13, the absorption layer 14, the prevention layer 15, and the stabilization layer 21 from the substrate 11 side.

As the stabilizing layer 21, oxides including Ta, oxynitrides, and boron oxides can be used. Examples of oxides including Ta, nitrogen oxides, and boron oxides include TaO, Ta ₂ O ₅ , TaON, TaCON, TaBO, TaBON, TaBCON, TaHfO, TaHfON, TaHfCON, TaSiO, TaSiON, and TaSiCON.

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

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

In this way, since the reflective mask base 10B has the stabilizing layer 21 on the prevention layer 15, the cleaning resistance of the prevention layer 15 can be further improved. By having the stabilizing layer 21, a strong and stable film can be formed with good reproducibility, and the characteristics of the reflective mask base and the reflective mask can be stabilized.

Since the reflective mask base 10B has the prevention layer 15 on the absorption layer 14 containing Sn, the surface of the absorption layer 14 does not come into contact with oxygen when the stabilizing layer 21 is formed on the prevention layer 15. For example, when the reactive sputtering method is used to form the stabilizing layer 21, as described above, a mixed gas of oxygen mixed with an inert gas such as He, Ar, or Kr, or nitrogen is selectively added to the inert gas, Furthermore, a mixed gas mixed with oxygen is used as a sputtering gas. Since the prevention layer 15 is formed on the absorption layer 14, when the stabilization layer 21 is formed, the surface of the absorption layer 14 does not come into contact with the mixed gas as the sputtering gas. Therefore, the surface of the absorption layer 14 is not oxidized, and it is possible to prevent the occurrence of precipitates on the surface of the absorption layer 14.

The reflective mask substrate 10B uses an oxide, oxynitride, or boron oxide containing Ta to form the stabilizing layer 21, whereby no change in the composition of the stabilizing layer 21 due to cleaning can be achieved, so that cleaning resistance can be obtained More excellent reflective mask base and reflective mask.

By setting the film thickness of the stabilizing layer 21 to 10 nm or less, the reflective mask substrate 10B can achieve thinning of the reflective mask substrate 10B and thinning of the pattern of the reflective mask, while maintaining the thickness of the prevention layer 15 Wash resistance.

Furthermore, as shown in FIG. 8, the reflective mask base 10B may be provided with a hard mask layer 17 on the stabilizing layer 21 in the same manner as the reflective mask base 10A of the first embodiment shown in FIG. 4. [Example]

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

[Example 1] The reflective mask base 100 is shown in FIG. 9. The reflective mask substrate 100 does not have the prevention layer 15 on the absorption layer 14 in the reflective mask substrate 10A of the first embodiment shown in FIG. 1. (Fabrication of Reflective Mask Base) SiO ₂ -TiO ₂ based glass substrate (approximately 152 mm square and approximately 6.3 mm thick) was used as the substrate for film formation. Furthermore, the thermal expansion coefficient of the glass substrate is 0.02×10 ^-7 /°C or less. The glass substrate is ground and processed into a smooth surface with a surface roughness of rms roughness Rq of 0.15 nm or less and a flatness of 100 nm or less. On the back surface of the glass substrate, a magnetron sputtering method was used to form a Cr layer with a film thickness of about 100 nm to form a back conductive layer (conductive film) for electrostatic chuck. The sheet resistance of the Cr layer is about 100 Ω/□. After fixing the glass substrate with the Cr film, the Si film and the Mo film were alternately formed on the surface of the glass substrate by ion beam sputtering, and this was repeated for 40 cycles. The film thickness of the Si film is set to about 4.5 nm, and the film thickness of the Mo film is set to about 2.3 nm. By this, a reflective layer (multilayer reflective film) with a total film thickness of about 272 nm ((Si film: 4.5 nm+Mo film: 2.3 nm)×40) was formed. Thereafter, a Ru layer (thickness of about 2.5 nm) was formed on the reflective layer by ion beam sputtering to form a protective layer (protective film). Next, by a magnetron sputtering method, an absorber layer (absorber film) with a thickness of 40 nm including a Sn-Ta alloy is formed on the protective layer. Ar gas is used as the sputtering gas. Among the targets used in sputtering, Sn is 60 at% and Ta is 40 at%, but the Ta content in the sputtered absorption layer is 48 at%. In addition, the Sn content and Ta content in the absorption layer were measured using fluorescent X-ray analysis (XRF) (manufactured by Olympus, Delta). In this way, the reflective mask base 100 shown in FIG. 9 is manufactured. The film thickness of the absorption layer was measured by XRR using an X-ray diffraction device (manufactured by RIGAKU Co., Ltd., SmartLab HTP). Furthermore, from the results of X-ray diffraction (XRD) measurement using this device, it was confirmed that the absorption layer containing the Sn-Ta alloy was amorphous.

(Observation of the surface of the reflective mask substrate) The surface of the reflective mask substrate 100 was observed using a scanning electron microscope (manufactured by Carl Zeiss, Ultra60). The observation result of the surface of the reflective mask base is shown in FIG. As shown in FIG. 10, particles are observed on the surface of the reflective mask base. The fine particles were analyzed by energy dispersive X-ray analysis (EDX), and as a result, it was confirmed that the fine particles were formed of tin oxide. It is believed that the fine particles on the surface of the absorption layer are produced when the absorption layer is exposed to the atmosphere, and Sn contained in the absorption layer reacts with oxygen in the atmosphere. Such fine particles exist in the absorption layer as a pattern defect and remain in the reflective mask after being etched, which is undesirable.

[Example 2] In this example, a 4 nm TaN film was formed on the absorption layer of the reflective mask substrate 100 produced in Example 1 as a preventive layer, and the reflective mask substrate 10A shown in FIG. 1 was produced. In addition, a reactive sputtering method was used for the prevention layer, and a mixed gas of Ar and nitrogen was used as the sputtering gas. The flow rate of Ar was 70 sccm, and the flow rate of nitrogen was 2 sccm. Furthermore, the reflective reticle substrate 100 produced in Example 1 was moved from the film forming room of the film forming apparatus used in the formation of the absorption layer to the storage room, and the storage room was stored in a high vacuum state until it was absorbed A prevention layer is formed on the layer.

(Observation of the surface of the reflective mask base) The surface of the reflective mask base 10A was observed using a scanning electron microscope. The observation result of the surface of the absorption layer of the reflective mask base 10A is shown in FIG. 11. As shown in FIG. 11, no particles are generated on the surface of the absorption layer of the reflective mask base 10A. It can be said that the reason is that, since there is a prevention layer on the surface of the absorption layer, oxygen in the atmosphere will not come into contact with Sn contained in the absorption layer.

[Example 3] In this example, a 2 nm Ta-containing prevention layer was formed on the absorption layer of the reflective mask substrate 100 produced in Example 1 by magnetron sputtering, and further, by reactivity A sputtering method is used to form a 2 nm stable layer containing TaO on the prevention layer. With this, the reflective mask base 10B shown in FIG. 7 is produced. In addition, when forming the prevention layer by the magnetron sputtering method, Ar gas is used as the sputtering gas. When forming the stable layer by the reactive sputtering method, a mixed gas in which Ar and oxygen are mixed is used as the sputtering gas, the flow rate of Ar is set to 40 sccm, and the flow rate of oxygen is set to 30 sccm. Furthermore, the reflective reticle substrate 100 produced in Example 1 was moved from the film forming room of the film forming apparatus used in the formation of the absorption layer to the storage room, and the storage room was stored in a high vacuum state until it was absorbed A prevention layer is formed on the layer.

XRR was used to measure the prevention layer and the stabilization layer of the reflective mask substrate 10B after film formation. As a result, it was found that the film thickness of Ta was 0.9 nm and the film thickness of TaO was 4.6 nm. The reason is considered to be that when the TaO film is formed on the Ta film, oxygen contained in the sputtering gas reacts with Ta of the Ta film to become a TaO film and expand.

Thereafter, the reflective mask substrate 10B shown in FIG. 7 is dry-etched using a dry etching device. After the dry etching system uses the F-based gas to remove the prevention layer and the stable layer, the Cl-based gas is used to remove the absorption layer.

(Observation of the surface of the reflective mask substrate) The surface of the reflective mask substrate 10B was observed using a scanning electron microscope. The observation result of the absorption layer on the surface of the reflective mask base 10B is shown in FIG. 12. As shown in FIG. 12, no precipitates such as fine particles were observed on the surface of the reflective mask base. In this example, when forming the prevention layer, only Ar was used as the sputtering gas. Therefore, since the surface of the absorption layer is not exposed to the environment containing oxygen, Sn existing on the surface of the absorption layer does not react with oxygen. By this, it can be said that the generation of precipitates on the surface of the absorption layer is suppressed.

[Example 4] (Fabrication of Reflective Photomask Base) In this example, when the absorption layer containing Sn-Ta alloy was formed into film in Example 3, instead of Sn-Ta alloy target, both Sn target and Ta target were used. Binary sputtering method. Then, Ar gas was used as the 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 performing binary sputtering, the charging of the Sn target and the Ta target started simultaneously. Regarding the end timing of the charging of the Sn target and the Ta target, the Sn target is set to 520 seconds after the start of charging, and the Ta target is set to 608 seconds after the start of charging. In this way, an absorption layer containing a Sn-Ta alloy with a thickness of 35 nm and a prevention layer containing Ta with a thickness of 2 nm on the absorption layer are continuously formed by one sputtering. Thereafter, on the prevention layer, in the same manner as in Example 3, a 2 nm stable layer containing TaO was formed using a reactive sputtering method. With this, the reflective mask base 10B shown in FIG. 7 is produced. Furthermore, the content of Ta in the sputtered absorption layer was measured using XRF, and the result was 35%.

(Observation of the surface of the reflective mask substrate) The surface of the reflective mask substrate 10B produced in this example was observed using a scanning electron microscope. As a result, no precipitates such as fine particles were observed on the surface of the reflective mask substrate 10B. As in Example 2 or Example 3, in the case where the absorption layer and the prevention layer are formed by two sputterings, it is necessary to form the reflective mask base 100 produced by forming the absorption layer in Example 1 from the absorption layer The film-forming chamber of the film-forming apparatus used in the formation was returned to the storage room. The storage room maintains a high vacuum, but due to a small amount of residual oxygen, there is a danger of generating oxide particles on the surface of the absorption film. 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 base 10B, the generation of oxide fine particles in the storage room can be reduced. Moreover, since it can be completed by one sputtering, the manufacturing time of the reflective mask base 10B can be shortened.

As described above, the embodiments have been described, but the above embodiments are proposed as examples, and the present invention is not limited by the above embodiments. The above-described embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. Such embodiments or changes are included in the scope or gist of the invention, and are included in the invention described in the scope of the patent application and its equivalent scope.

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

10A, 10B ‧‧‧reflective mask base 11‧‧‧ substrate 11a‧‧‧first main surface 11b‧‧‧second main surface 12‧‧‧reflective layer 13‧‧‧protective layer 14‧‧‧absorption layer 15‧‧‧Prevent layer 17‧‧‧ Hard mask layer 18‧‧‧ Back conductive layer 19‧‧‧Resist layer 20‧‧‧Reflective mask 21‧‧‧Stabilization layer 100‧‧‧Reflective light Cover base 141‧‧‧absorber pattern 191‧‧‧resist pattern S11～S14‧‧‧step X, Y, Z‧‧‧ direction

FIG. 1 is a schematic cross-sectional view of a reflective mask base of the first embodiment. 2 is a flowchart showing an example of a method of manufacturing a reflective mask base. FIG. 3 is a schematic cross-sectional view showing an example of other forms of the reflective mask base. FIG. 4 is a schematic cross-sectional view showing an example of other forms of the reflective mask base. 5 is a schematic cross-sectional view showing an example of the structure of a reflective mask. 6(a)-(c) are diagrams illustrating the manufacturing steps of the reflective mask. 7 is a schematic cross-sectional view of a reflective mask base in a second embodiment. FIG. 8 is a schematic cross-sectional view showing an example of other forms of the reflective mask base. 9 is a schematic cross-sectional view of the reflective mask base of Comparative Example 1. FIG. 10 is a graph showing the observation results of the surface of the absorption layer of the reflective mask base of Comparative Example 1. FIG. 11 is a diagram showing the observation results of the surface of the absorption layer of the reflective mask base of Example 1. FIG. 12 is a diagram showing the observation results of the surface of the absorption layer of the reflective mask base of Example 2. FIG.

10A‧‧‧Reflective mask base

11‧‧‧ substrate

11a‧‧‧1st main face

12‧‧‧Reflective layer

13‧‧‧Protective layer

14‧‧‧absorbent layer

15‧‧‧Prevention layer

X, Y, Z‧‧‧ direction

Claims (15)

A reflective reticle base, which has a reflection layer that reflects EUV light and an absorption layer that absorbs EUV light in order from the substrate side on the substrate; and The absorption layer contains Sn, An anti-oxidation layer for preventing oxidation of the absorption layer is provided on the absorption layer. The reflective reticle substrate according to claim 1, wherein the above-mentioned 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 reflective reticle substrate according to claim 2, wherein the above-mentioned prevention layer contains a material selected from the group consisting of Ta elemental substance, Ru elemental substance, Cr elemental substance, Ti elemental substance, Si elemental substance, Ta nitride, Ru nitride, Cr nitride, Ti One or more components in the group consisting of nitrides, Si nitrides, Ta borides, Ru borides, Cr borides, Ti borides, Si borides, and Ta boron nitrides. The reflective reticle substrate according to any one of claims 1 to 3, wherein the prevention layer contains one or more elements selected from the group consisting of He, Ne, Ar, Kr, and Xe. The reflective reticle substrate according to any one of claims 1 to 4, wherein the film thickness of the above-mentioned prevention layer is 10 nm or less. The reflective reticle substrate according to any one of claims 1 to 5, wherein the absorption layer contains one or more elements selected from the group consisting of Ta, Cr, and Ti. The reflective reticle substrate according to any one of claims 1 to 6, which has a stabilizing layer on the prevention layer. The reflective reticle substrate according to claim 7, wherein the above-mentioned stabilizing layer contains one or more kinds selected from the group consisting of oxides containing Ta, nitrogen oxides, and boron oxides. The reflective reticle substrate according to claim 7 or 8, wherein the film thickness of the above-mentioned stabilizing layer is 10 nm or less. The reflective reticle substrate according to any one of claims 1 to 9, which has a protective layer between the reflective layer and the absorption layer. The reflective reticle substrate according to any one of claims 1 to 10, which has a hard reticle layer on the above-mentioned prevention layer or a layer on the most surface side of the above-mentioned prevention layer. The reflective reticle substrate 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 reticle having a pattern formed on the above-mentioned absorption layer of the reflective reticle substrate according to any one of claims 1 to 12. A method for manufacturing a reflective mask base includes a reflective mask base having a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light on the substrate from the side of the substrate. The method includes the following steps: Forming the reflective layer on the substrate; Forming the above-mentioned absorption layer containing Sn on the above-mentioned reflection layer; and An anti-oxidation layer for preventing oxidation of the absorption layer is formed on the absorption layer. The manufacturing method of the reflective mask base according to claim 14, which continuously performs the step of forming the above-mentioned absorption layer and the step of forming the above-mentioned prevention layer in the film forming chamber by using a binary sputtering method.

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