JP2022087344A - Multilayer reflective film-equipped substrate, reflective mask blank, reflective mask, and method for fabricating semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer reflective film-equipped substrate capable of: adequately lowering reflectance of a multilayer film with respect to EUV exposure light; and preventing occurrence of a phenomenon in which a surface of a protective film on a multilayer reflective film swells and a phenomenon in which the protective film is detached.

SOLUTION: A multilayer reflective film-equipped substrate 110 includes a multilayer reflective film 5 and a protective film 6, in this order, on a main surface of a substrate 1. The substrate 1 has silicon, titanium, and oxygen as main components and also contains hydrogen. The multilayer reflective film 5 has a structure in which low refractive index layers and high refractive index layers are alternately laminated. The multilayer reflective film 5 contains hydrogen. Atomic number density of hydrogen in the multilayer reflective film 5 is equal to or less than 7.0×10^-3 atoms/nm³.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a reflective mask used for manufacturing a semiconductor device and the like, and a substrate with a multilayer reflective film and a reflective mask blank used for manufacturing the reflective mask. The present invention also relates to a method for manufacturing a semiconductor device using the reflective mask.

Exposure devices in semiconductor device manufacturing are evolving while gradually shortening the wavelength of the light source. In order to realize finer pattern transfer, EUV lithography using extreme ultraviolet rays (EUV: Extreme Ultra Violet, hereinafter may be referred to as EUV light) having a wavelength near 13.5 nm has been developed. In EUV lithography, a reflective mask is used because there are few materials that are transparent to EUV light. Typical reflective masks include a binary type reflective mask and a phase shift type reflective mask (halftone phase shift type reflective mask). The binary reflective mask has a relatively thick absorber pattern that absorbs EUV light well. The phase-shift type reflective mask dims the EUV light by light absorption and generates reflected light whose phase is almost inverted (phase inversion of about 180 degrees) with respect to the reflected light from the multilayer reflective film. It has a thin absorber pattern (phase shift pattern).

Techniques related to such a reflective mask for EUV lithography and a mask blank for producing the same are described in Patent Documents 1 to 3.

Patent Document 1 describes that a treatment of irradiating a multilayer reflective film in a region outside the mask pattern region with a laser beam or an electron beam to heat the multilayer reflective film is performed. By performing this treatment, the diffusion of the high-refractive index material and the low-refractive index material of the multilayer reflective film is promoted, and the reflectance of the EUV light of the multilayer reflective film is lowered.

Patent Document 2 describes TiO ₂ -SiO ₂ glass used in EUV lithography photomasks and the like. This document describes that the hydrogen content in the TiO ₂ -SiO ₂ glass is preferably 5 × 10 ¹⁷ molecules / cm ³ or more. Further, it is also described that it is preferable to add OH to the TiO ₂ -SiO ₂ glass.

Patent Document 3 describes that in a multilayer structure of a silicon layer and a molybdenum layer of a soft X-ray multilayer film reflector, a hydrogenated layer obtained by hydrogenating silicon is provided at the interface between the silicon layer and the molybdenum layer. It is described that by providing a hydrogenated layer, mutual reaction and diffusion at the interface between the silicon layer and the molybdenum layer can be suppressed.

International Publication No. 2010/026998 JP 2011-162359 Japanese Patent Application Laid-Open No. 5-297194

In EUV lithography, a projection optical system consisting of a large number of reflectors is used because of the light transmittance. Then, EUV light is obliquely incident on the reflective mask so that the plurality of reflecting mirrors do not block the projected light (exposure light). Currently, the mainstream angle of incidence is 6 degrees with respect to the vertical surface of the substrate of the reflective mask.

In EUV lithography, since the exposure light is incident at an angle, there is a unique problem called a shadowing effect. The shadowing effect is a phenomenon in which an exposure light is obliquely incident on an absorber pattern having a three-dimensional structure to form a shadow, and the dimensions and positions of the pattern transferred and formed change. The three-dimensional structure of the absorber pattern becomes a wall and a shadow is formed on the shaded side, and the dimensions and position of the transfer-formed pattern change. For example, there is a difference in the dimensions and positions of the transfer patterns between the two when the direction of the absorber pattern to be arranged is parallel to the direction of the obliquely incident light and when the direction is perpendicular to the direction of the oblique incident light, which lowers the transfer accuracy.

In the reflective mask, it is required to reduce the above-mentioned shadowing effect because of the demand for ultra-fine and highly accurate pattern formation. Therefore, in the reflective mask, it is considered to reduce the film thickness of the thin film pattern (absorber pattern, phase shift pattern). However, it is unavoidable that the reflectance to EUV light becomes higher than before by reducing the film thickness of the thin film pattern.

Generally, pattern transfer in EUV lithography is performed by step-and-scanning the transfer pattern of the reflective mask onto the transfer target. In this step-and-scan, a plurality of the same transfer patterns are exposed and transferred onto a transfer target by repeating exposure transfer and step movement. At that time, a plurality of transfer patterns are exposed and transferred on the transfer target with almost no space between them. Therefore, the reflected light from the outer peripheral region of the region where the transfer pattern of the thin film of the reflective mask is formed is overlapped and exposed, which is a state of so-called superposition exposure. If the reflectance of the thin film pattern is higher than before, there is a risk that unnecessary exposure will occur in the region where the superposition exposure of the transfer target is performed.

The present inventors have attempted the method disclosed in Patent Document 1 in order to reduce the reflectance of the outer peripheral region of the region where the transfer pattern of the reflective mask is formed to EUV light. Specifically, a treatment of irradiating a laser beam was performed to promote diffusion between the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer of the multilayer reflective film. As a result of this treatment, it was newly found that the phenomenon that the surface of the protective film on the multilayer reflective film swells and the phenomenon that the protective film peels off may occur. It was also found that this phenomenon may occur even when the electron beam irradiation treatment is performed or the heat treatment is performed. When these phenomena occur, it becomes impossible to continue the process for advancing the diffusion between the constituent elements of the low refractive index layer of the multilayer reflective film and the constituent elements of the high refractive index layer, and the multilayer reflection cannot be continued. This has been a problem because the reflectance of the film to the EUV exposure light cannot be sufficiently reduced. In addition, there is also a problem that dust is generated due to the rupture of the protective film, and defects frequently occur in the manufactured reflective mask.

Therefore, according to the present invention, it is possible to sufficiently reduce the reflectance of the multilayer reflective film to the EUV exposure light, and the phenomenon that the surface of the protective film on the multilayer reflective film swells and the protective film peels off occurs. It is an object of the present invention to provide a substrate with a multilayer reflective film capable of preventing the above.

Another object of the present invention is to provide a reflective mask blank and a reflective mask manufactured by using the substrate with a multilayer reflective film, and a method of manufacturing a semiconductor device using the reflective mask.

As a result of diligent research, the present inventors turned the hydrogen existing in the multilayer reflective film into a gas due to the heat generation of the multilayer reflective film due to irradiation of laser light, etc., and tried to separate from the multilayer reflective film to protect the multilayer reflective film. It was found that the protective film floats from the multilayer reflective film by accumulating at the interface with the film. Furthermore, it was also found that the temperature rise between the multilayer reflective film and the protective film causes thermal expansion of the gaseous hydrogen trapped between the multilayer reflective film and the protective film, resulting in a phenomenon in which the protective film bursts.

On the other hand, it was found that hydrogen and OH groups are contained in the substrate of the mask blank for manufacturing the reflective mask, and these cannot be eliminated. It was also found that a phenomenon of hydrogen and OH groups moving from the substrate to the multilayer reflective film occurs, and it is difficult to prevent the phenomenon. Based on these findings, the present inventors have conducted further diligent research and have come to the conclusion that the above technical problems can be solved by using a substrate with a multilayer reflective film having the following configuration.

(Structure 1)
A substrate with a multilayer reflective film having a multilayer reflective film and a protective film in this order on the main surface of the substrate.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less.

(Structure 2)
The substrate with a multilayer reflective film according to Configuration 1, wherein the high refractive index layer contains silicon and the low refractive index layer contains molybdenum.

(Structure 3)
Configuration 1 characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by secondary ion mass spectrometry is 1.0 × 10 ¹⁹ atoms / cm ³ or more. Alternatively, the substrate with a multilayer reflective film according to 2.

(Structure 4)
The substrate with a multilayer reflective film according to any one of configurations 1 to 3, wherein the protective film contains ruthenium.

(Structure 5)
The multilayer reflective film has a mixed region on the main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed, and the surface reflectance of the mixed region with respect to EUV light is the same. The substrate with a multilayer reflective film according to any one of configurations 1 to 4, wherein the refractive index is lower than the surface reflectance for EUV light in a region other than the above.

(Structure 6)
A mask blank in which a multilayer reflective film, a protective film, and a thin film for pattern formation are provided in this order on the main surface of the substrate.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less.

(Structure 7)
The mask blank according to the configuration 6, wherein the high refractive index layer contains silicon, and the low refractive index layer contains molybdenum.

(Structure 8)
The configuration 6 is characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by secondary ion mass spectrometry is 1.0 × 10 ¹⁹ atoms / cm ³ or more. Or the mask blank according to 7.

(Structure 9)
The mask blank according to any one of configurations 6 to 8, wherein the protective film contains ruthenium.

(Structure 10)
The multilayer reflective film has a mixed region on the main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed, and the surface reflectance of the mixed region with respect to EUV light is the above. The mask blank according to any one of configurations 6 to 9, wherein the pattern-forming thin film has a lower surface reflectance to EUV light.

(Structure 11)
A reflective mask having a multilayer reflective film, a protective film, and a thin film pattern on the main surface of the substrate in this order.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less.
The multilayer reflective film has a mixed region in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed in the outer peripheral region of the region where the thin film pattern is provided on the main surface. A reflective mask characterized in that the surface reflectance of the mixed region to EUV light is lower than the surface reflectance of the thin film pattern to EUV light.

(Structure 12)
11. The reflective mask according to configuration 11, wherein the high refractive index layer contains silicon, and the low refractive index layer contains molybdenum.

(Structure 13)
The configuration 11 is characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by secondary ion mass spectrometry is 1.0 × 10 ¹⁹ atoms / cm ³ or more. Or the reflective mask according to 12.

(Structure 14)
The reflective mask according to any one of configurations 11 to 13, wherein the protective film contains ruthenium.

(Structure 15)
A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the reflective mask according to any one of configurations 11 to 14.

According to the present invention, it is possible to sufficiently reduce the reflectance of the multilayer reflective film to EUV exposure light, and the phenomenon that the surface of the protective film on the multilayer reflective film swells and the protective film peels off occurs. It is possible to provide a substrate with a multilayer reflective film capable of suppressing the above.

Further, according to the present invention, it is possible to provide a reflective mask blank and a reflective mask partially having the same configuration as the substrate with a multilayer reflective film, and a method for manufacturing a semiconductor device using the reflective mask. ..

It is sectional drawing of an example of the substrate with a multilayer reflective film. It is sectional drawing of an example of a reflective mask blank. It is a process drawing which showed the manufacturing method of the reflection type mask by the sectional schematic diagram.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. It should be noted that the following embodiments are embodiments for specifically explaining the present invention, and do not limit the scope of the present invention.

FIG. 1 is a schematic cross-sectional view of the substrate 110 with a multilayer reflective film of the present embodiment. As shown in FIG. 1, the substrate 110 with a multilayer reflective film of the present embodiment includes a multilayer reflective film 5 and a protective film 6 on the substrate 1 in this order. The multilayer reflective film 5 is a film for reflecting exposure light, and is composed of a multilayer film in which low refractive index layers and high refractive index layers are alternately laminated. The protective film 6 is a film for protecting the multilayer reflective film 5 from damage caused by dry etching and cleaning in the manufacturing process of the reflective mask 200 described later. Further, the protective film 6 can also protect the multilayer reflective film 5 when the black defect of the mask pattern is corrected by using the electron beam (EB). The substrate 110 with a multilayer reflective film of the present embodiment may include a back surface conductive film 2 on the back surface of the substrate 1 (the main surface opposite to the main surface on which the multilayer reflective film 5 is formed).

The reflective mask blank 100 can be manufactured by using the substrate 110 with the multilayer reflective film of the present embodiment. FIG. 2 is a schematic cross-sectional view of an example of the reflective mask blank 100. As shown in FIG. 2, the reflective mask blank 100 further includes an absorber film (pattern forming thin film) 7 on the protective film 6. By using the reflective mask blank 100 of the present embodiment, it is possible to obtain a reflective mask 200 having a multilayer reflective film 5 having a high reflectance for EUV light.

In the present specification, "having a film B on the film A" means not only when the film B is arranged in contact with the surface of the film A, but also when another film is placed between the film A and the film B. Including the case where it exists. Further, in the present specification, "the film B is arranged in contact with the surface of the film A" means that the film B is placed on the surface of the film A without interposing another film between the film A and the film B. It means that they are arranged so as to be in contact with each other.

<Substrate 110 with multilayer reflective film>
Hereinafter, the substrate 110 with a multilayer reflective film of the present embodiment will be described in detail. The substrate 110 with a multilayer reflective film includes a substrate 1, a multilayer reflective film 5, and a protective film 6.

<< Board 1 >>
The substrate 1 contains silicon, titanium and oxygen as main components, and further contains hydrogen. The hydrogen in this case includes those contained in the state of OH groups. As an example of the substrate 1 containing silicon, titanium and oxygen as main components, SiO ₂ -TiO ₂ glass can be mentioned. The SiO ₂ -TiO ₂ system glass is a silica glass containing TiO ₂ and is a low thermal expansion material having a coefficient of thermal expansion smaller than that of quartz glass. When the substrate 1 is a SiO ₂ -TiO ₂ system glass, the substrate 1 contains hydrogen and OH groups.

The atomic number density of hydrogen in the substrate 1 obtained by analyzing the substrate 1 by the secondary ion mass spectrometry (SIMS) is 1.0 × 10 ¹⁹ atoms / cm ³ or more. It is preferably 2.0 × 10 ¹⁹ atoms / cm ³ or more, more preferably. On the other hand, the atomic number density of hydrogen in the substrate 1 is preferably 5.0 × 10 ²¹ atoms / cm ³ or less, and more preferably 3.0 × 10 ²¹ atoms / cm ³ or less. If the hydrogen content in the substrate 1 is too high, the amount of hydrogen released from the substrate 1 becomes large, and a large amount of the hydrogen is taken into the multilayer reflective film 5. The hydrogen in the substrate 1 detected by the analysis by SIMS includes a state of being bonded to Si, a state of an OH group, a state of being present as an ion, a state of being present as a molecule, and the like. Therefore, the numerical value of the atomic number density of hydrogen in the substrate 1 measured by the analysis by SIMS includes hydrogen in the OH group.

The concentration of the OH group in the substrate 1 is preferably 50 ppm or more, more preferably 60 ppm or more. The concentration of the OH group in the substrate 1 can be measured by a known method, for example, the method described in Japanese Patent No. 4792705.

The first main surface on the side of the substrate 1 on which the multilayer reflective film 5 is formed is preferably surface-treated so as to have a predetermined flatness from the viewpoint of improving the pattern transfer accuracy. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.05 μm or less in the region of 132 mm × 132 mm on the main surface on the side where the transfer pattern of the substrate 1 is formed. It is 0.03 μm or less. Further, the second main surface (back surface) on the side opposite to the side on which the multilayer reflective film 5 is formed is adsorbed by the electrostatic chuck when the reflective mask is set in the exposure apparatus. The flatness of the second main surface is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.03 μm or less in a region of 142 mm × 142 mm.

In addition, the high surface smoothness of the substrate 1 is also important. The surface roughness of the first main surface of the substrate 1 is preferably 0.15 nm or less in root mean square roughness (Rms), more preferably 0.10 nm or less in Rms. The surface smoothness can be measured with an atomic force microscope.

Further, the substrate 1 preferably has high rigidity in order to prevent deformation of the film (multilayer reflective film 5 or the like) formed on the substrate 1 due to film stress. In particular, the substrate 1 preferably has a high Young's modulus of 65 GPa or more.

<< Multilayer Reflective Film 5 >>
The multilayer reflective film 5 imparts a function of reflecting EUV light in the reflective mask 200. The multilayer reflective film 5 is a multilayer film in which each layer containing elements having different refractive indexes as main components is periodically laminated.

Generally, the multilayer reflective film 5 includes a thin film (high refractive index layer) of a light element or a compound thereof which is a high refractive index material and a thin film (low refractive index layer) of a heavy element or a compound thereof which is a low refractive index material. ) And are alternately laminated for about 40 to 60 cycles (pairs) to use a multilayer film.

The multilayer reflective film 5 includes a laminated structure of a "high refractive index layer / low refractive index layer" in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 1 side. This laminated structure may be laminated for a plurality of cycles with one "high refractive index layer / low refractive index layer" as one cycle. Alternatively, the multilayer reflective film 5 includes a laminated structure of a "low refractive index layer / high refractive index layer" in which a low refractive index layer and a high refractive index layer are laminated in this order from the substrate 1 side. This laminated structure may be laminated for a plurality of cycles with one "low refractive index layer / high refractive index layer" as one cycle. The outermost layer of the multilayer reflective film 5, that is, the surface layer of the multilayer reflective film 5 on the side opposite to the substrate 1 side is preferably a high refractive index layer. When the high refractive index layer and the low refractive index layer are laminated in this order from the substrate 1 side, the uppermost layer becomes the low refractive index layer. In this case, since the low refractive index layer is the outermost surface of the multilayer reflective film 5, the outermost surface of the multilayer reflective film 5 is easily oxidized, and the reflectance of the reflective mask 200 is reduced. Therefore, it is preferable to further form a high refractive index layer on the low refractive index layer of the uppermost layer. On the other hand, when the low refractive index layer and the high refractive index layer are laminated in this order from the substrate 1 side, the uppermost layer becomes the high refractive index layer. In this case, it is not necessary to form a further high refractive index layer.

As the high refractive index layer, for example, a material containing silicon (Si) can be used. As a material containing Si, in addition to elemental substance Si, Si contains at least one element selected from boron (B), carbon (C), zirconium (Zr), nitrogen (N) and oxygen (O). Si compounds can be used. By using a high refractive index layer containing Si, a reflective mask 200 having excellent reflectance of EUV light can be obtained.

As the low refractive index layer, for example, at least one metal unit selected from molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and platinum (Pt), or an alloy thereof can be used.

In the substrate 110 with a multilayer reflective film of the present embodiment, it is preferable that the low refractive index layer is a layer containing molybdenum (Mo) and the high refractive index layer is a layer containing silicon (Si). For example, as the multilayer reflective film 5 for reflecting EUV light having a wavelength of 13 nm to 14 nm, a Mo / Si periodic laminated film in which layers containing Mo and layers containing Si are alternately laminated for about 40 to 60 cycles is preferably used. ..

When the high-refractive index layer, which is the uppermost layer of the multilayer reflective film 5, is a layer containing silicon (Si), silicon containing silicon and oxygen is provided between the uppermost layer (layer containing Si) and the protective film 6. An oxide layer may be formed. In this case, the mask cleaning resistance can be improved.

In the substrate 110 with a multilayer reflective film of the present embodiment, the multilayer reflective film 5 is characterized by containing hydrogen. The atomic number density of hydrogen in the multilayer reflective film 5 is 7.0 × 10 ^-3 atoms / nm ³ or less, preferably 6.5 × 10 ^-3 atoms / nm ³ or less, and more preferably 6. It is 0 × 10 ^-3 atoms / nm ³ or less. On the other hand, the atomic number density of hydrogen in the multilayer reflective film 5 is preferably 1.0 × 10 ^-4 atoms / nm ³ or more, and more preferably 2.0 × 10 ^-4 atoms / nm ³ or more. The atomic number density of hydrogen in the multilayer reflective film 5 can be measured by, for example, secondary ion mass spectrometry (SIMS).

Generally, when the substrate 1 is composed of a SiO ₂ -TiO ₂ system glass, the SiO ₂ -TiO ₂ system glass always contains a predetermined amount or more of hydrogen and OH groups, so that the substrate 1 always contains hydrogen and OH groups. Is difficult to completely eliminate. Therefore, the hydrogen and OH groups released from the substrate 1 are also incorporated into the multilayer reflective film 5 formed on the substrate 1. In particular, when the highly refracting material in the multilayer reflective film 5 is silicon, since silicon easily takes in hydrogen, such a phenomenon occurs remarkably.

It is difficult for the multilayer reflective film 5 to make the film stress zero at the time of film formation. In order to reduce the film stress of the multilayer reflective film 5, heat treatment is often performed. During this heat treatment, the hydrogen and OH groups of the substrate 1 are easily incorporated into the multilayer reflective film 5. Further, when the resist film 8 is formed on the absorber film 7 of the mask blank 100 described later, a heat treatment (PAB: Pre-Applied break) for drying is performed after applying the resist liquid by a spin coating method or the like. Will be. During this heat treatment, the hydrogen and OH groups of the substrate 1 are easily incorporated into the multilayer reflective film 5. Further, when the resist film 8 is a chemically amplified resist, a heat treatment (PEB: Post Exposure Bake) is performed after the transfer pattern is exposed and drawn on the resist film 8 with an electron beam. Further, even after the development treatment of the resist film 8 is performed, the heat treatment (Post Bake) is performed. Even during these heat treatments, the hydrogen and OH groups of the substrate 1 are easily incorporated into the multilayer reflective film 5.

When hydrogen and OH groups are incorporated into the multilayer reflective film 5, the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are diffused from each other by irradiating the multilayer reflective film 5 with a laser or the like. When the treatment for lowering the refractive index is performed, a phenomenon occurs in which hydrogen and OH groups incorporated in the multilayer reflective film 5 are vaporized and accumulated between the multilayer reflective film 5 and the protective film 6. In this case, since the protective film 6 on the multilayer reflective film 5 swells and the protective film 6 itself bursts, laser irradiation and the like cannot be sufficiently performed, and a predetermined region of the multilayer reflective film 5 cannot be sufficiently performed. There is a problem that the reflectance of (a light-shielding region on the outer periphery of the transfer pattern forming region) to EUV light cannot be sufficiently reduced.

According to the substrate 110 with the multilayer reflective film of the present embodiment, the atomic number density of hydrogen in the multilayer reflective film 5 is suppressed within the above range. As a result, when laser irradiation or the like is performed to reduce the reflectance of the multilayer reflective film 5, hydrogen incorporated in the multilayer reflective film 5 is vaporized and between the multilayer reflective film 5 and the protective film 6. It is possible to suppress the occurrence of the phenomenon of accumulation in the. As a result, it is possible to sufficiently reduce the reflectance of the predetermined region of the multilayer reflective film 5 (such as the light-shielding region on the outer periphery of the transfer pattern forming region) to the EUV light, and a reflective mask having high pattern transfer accuracy can be manufactured. It is possible to obtain a substrate 110 with a multilayer reflective film and a reflective mask blank 100 that can be used.

The reflectance of the multilayer reflective film 5 of the present embodiment to EUV light alone is usually preferably 65% or more. Since the reflectance of the multilayer reflective film 5 is 65% or more, it can be preferably used as a reflective mask 200 for manufacturing a semiconductor device. The upper limit of reflectance is usually 73%. The film thickness and the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting the multilayer reflective film 5 can be appropriately selected depending on the exposure wavelength. Specifically, the film thickness and the number of cycles (number of pairs) of the low refractive index layer and the high refractive index layer constituting the multilayer reflective film 5 can be selected so as to satisfy the Bragg reflection law. In the multilayer reflective film 5, there are a plurality of high-refractive index layers and a plurality of low-refractive index layers, but the film thickness of the high-refractive index layers or the film thickness of the low-refractive index layers does not necessarily have to be the same. Further, the film thickness of the outermost surface (for example, the Si layer) of the multilayer reflective film 5 can be adjusted within a range that does not reduce the reflectance. The film thickness of the outermost surface high refractive index layer (for example, Si layer) is, for example, 3 nm to 10 nm.

In the substrate 110 with a multilayer reflective film of the present embodiment, the multilayer reflective film 5 may have 30 to 60 cycles (pairs) with a pair of low-refractive index layers and high-refractive index layers as one cycle (pair). It is more preferable to have 35 to 55 cycles (pairs), and even more preferably to have 35 to 45 cycles (pairs). As the number of cycles (number of pairs) increases, higher reflectance can be obtained, but the formation time of the multilayer reflective film 5 becomes longer. By setting the period of the multilayer reflective film 5 to an appropriate range, the multilayer reflective film 5 having a relatively high reflectance can be obtained in a relatively short time.

The multilayer reflective film 5 of the present embodiment can be formed by a sputtering method such as an ion beam sputtering method, a DC sputtering method, and an RF sputtering method. It is preferable to form the multilayer reflective film 5 by the ion beam sputtering method from the viewpoint that impurities are not easily mixed in the multilayer reflective film 5 and that the ion source is independent and the conditions can be set relatively easily.

The multilayer reflective film 5 of the present embodiment preferably has a film stress of 0.42 GPa or less, and more preferably 0.25 GPa or less. It is difficult to reduce the film stress to the above-mentioned film stress or less at the stage where the multilayer reflective film 5 is formed, and it is often the case that the film stress is reduced by performing heat treatment or the like as described above.

<< Protective film 6 >>
In order to protect the multilayer reflective film 5 from dry etching and cleaning in the manufacturing process of the reflective mask 200 described later, the protective film 6 is formed on the multilayer reflective film 5 or in contact with the surface of the multilayer reflective film 5. Can be done. The protective film 6 also has a role of protecting the multilayer reflective film 5 when correcting black defects in a thin film pattern using an electron beam (EB). Here, although FIGS. 1 and 2 show the case where the protective film 6 has one layer, the protective film 6 may have a laminated structure of two or more layers. The protective film 6 is formed of an etchant used when patterning the absorber film 7 and a material having resistance to a cleaning liquid. Since the protective film 6 is formed on the multilayer reflective film 5, the multilayer reflective film is used when the reflective mask 200 (EUV mask) is manufactured by using the substrate 110 having the multilayer reflective film 5 and the protective film 6. Damage to the surface of 5 can be suppressed. Therefore, the reflectance characteristics of the multilayer reflective film 5 with respect to EUV light are improved.

The reflective mask blank 100 of the present embodiment is resistant to the etching gas used for dry etching for patterning the absorber film 7 formed on the protective film 6 as the material of the protective film 6. The material can be selected.

When the absorber film 7 in contact with the surface of the protective film 6 is a thin film made of a material that can be etched by dry etching with a fluorine-based gas or dry etching with an oxygen-free chlorine-based gas (for example, including tantalum (Ta)). In the case of a thin film made of a material, for example, a material containing ruthenium as a main component can be selected as the material of the protective film 6. Examples of materials containing ruthenium as a main component include ruthenium alone, ru with titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), boron (B), and lanthanum (B). Examples include Ru alloys containing at least one metal selected from La), cobalt (Co), ruthenium (Re), and rhodium (Rh), and materials containing nitrogen thereof.

When the absorber film 7 in contact with the surface of the protective film 6 is a thin film made of a material containing ruthenium (Ru) and chromium (Cr) (predetermined RuCr-based material), silicon ( Silicon-based materials such as Si), materials containing silicon (Si) and oxygen (O), materials containing silicon (Si) and nitrogen (N), materials containing silicon (Si), oxygen (O) and nitrogen (N). Materials as well as materials selected from silicon-based materials containing silicon (Cr) or silicon (Cr) and at least one element of oxygen (O), nitrogen (N), and carbon (C). Can be used.

When the protective film 6 is configured to contain ruthenium (Ru) and rhodium (Rh), the protective film 6 has etching resistance to a mixed gas of chlorine-based gas and oxygen gas, etching resistance to chlorine-based gas, and fluorine-based gas. Etching resistance and sulphate overwater (SPM) cleaning resistance are improved. If the content of rhodium in the protective film 6 is too small, the effect of addition cannot be obtained, and if it is too large, the extinction coefficient k of the protective film 6 with respect to EUV light becomes high, so that the reflectance of the reflective mask 200 decreases. do. Therefore, the content of rhodium in the protective film 6 is preferably 15 atomic% or more and less than 50 atomic%, and more preferably 20 atomic% or more and 40 atomic% or less.

The protective film 6 can include at least one selected from N, C, O, H and B. The protective film 6 preferably further contains nitrogen (N). The crystallinity can be lowered by further containing nitrogen (N) in the protective film 6. As a result, the thin film can be densified, so that the resistance to etching gas and cleaning can be further increased. The nitrogen content in the protective film 6 is preferably larger than 1 atomic% and 20 atomic% or less, and more preferably 3 atomic% or more and 10 atomic% or less.

The protective film 6 preferably further contains oxygen (O). The crystallinity can be lowered by further containing oxygen (O) in the protective film 6. As a result, the protective film 6 can be densified, so that the resistance to etching gas and cleaning can be further increased. The oxygen content of the protective film 6 is preferably greater than 1 atomic% and 20 atomic% or less, and more preferably 3 atomic% or more and 10 atomic% or less.

The film thickness of the protective film 6 is not particularly limited as long as it can function as the protective film 6. From the viewpoint of the reflectance of EUV light, the film thickness of the protective film 6 is preferably 1.0 nm to 8.0 nm, and more preferably 1.5 nm to 6.0 nm. The extinction coefficient of the protective film 6 is preferably adjusted to 0.030 or less, more preferably 0.025 or less.

On the other hand, the protective film 6 may be configured to include a first layer and a second layer from the substrate 1 side. In this case, the second layer can be a thin film having a structure containing the above-mentioned ruthenium (Ru) and rhodium (Rh).

In order to prevent silicon (Si) from diffusing from the multilayer reflective film 5 to the protective film 6, the first layer of the protective film 6 is composed of ruthenium (Ru), magnesium (Mg), aluminum (Al), and tungsten. Select from (Ti), vanadium (V), chromium (Cr), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), rhodium (Rh), hafnium (Hf) and tungsten (W). It is preferable to include at least one of the above. In particular, when the first layer is a RuTi film, a RuZr film, or a RuAl film, the diffusion of silicon (Si) into the protective film 6 can be more reliably suppressed.

The Ru content of the first layer is preferably greater than 50 atomic% and less than 100 atomic%, more preferably 80 atomic% or more and less than 100 atomic%, and greater than 95 atomic% and 100 atoms. It is particularly preferable that it is less than%.

In the substrate 110 with a multilayer reflective film of the present embodiment, the Ru content of the second layer is preferably smaller than the Ru content of the first layer. For example, when the first layer is a RuTi film and the second layer is a RuRh film, even if the Ti content of the RuTi film of the first layer is relatively low, the silicon (Si) protective film 6 is coated. Diffusion can be suppressed. Therefore, since the Ru content of the second layer is smaller than the Ru content of the first layer, the resistance to etching gas and cleaning is further increased, and the diffusion of silicon (Si) into the protective film 6 is further increased. It can be suppressed.

The refractive index of the second layer of the protective film 6 is preferably smaller than the refractive index of the first layer. As a result, a substrate with a protective film (a substrate 110 with a multilayer reflective film having the protective film 6) can be manufactured without lowering the reflectance of EUV light from the multilayer reflective film 5 including the protective film 6. The refractive index of the second layer is preferably 0.920 or less, more preferably 0.885 or less.

The film thickness of the first layer of the protective film 6 is preferably 0.5 nm to 2.0 nm, and more preferably 1.0 nm to 1.5 nm. The film thickness of the second layer of the protective film 6 is preferably 1.0 nm to 7.0 nm, and more preferably 1.5 nm to 4.0 nm.

In EUV lithography, since there are few substances that are transparent to the exposure light, EUV pellicle that prevents foreign matter from adhering to the mask pattern surface is not technically easy. For this reason, pellicle-less operation that does not use pellicle has become the mainstream. Further, in EUV lithography, exposure contamination occurs such that a carbon film is deposited on the mask and an oxide film is grown due to EUV exposure. Therefore, when the reflective mask 200 for EUV exposure is used in the manufacture of a semiconductor device, it is necessary to perform frequent cleaning to remove foreign matter and contamination on the mask. Therefore, the reflective mask 200 for EUV exposure is required to have an order of magnitude more mask cleaning resistance than the transmissive mask for optical lithography. Since the reflective mask 200 has the protective film 6, the cleaning resistance to the cleaning liquid can be increased.

As a method for forming the protective film 6, the same method as a known film forming method can be adopted without particular limitation. Specific examples include a sputtering method and an ion beam sputtering method.

In the substrate 110 with a multilayer reflective film of the present embodiment, the multilayer reflective film 5 can have a mixed region on the first main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed. .. For example, when the low refractive index layer is a layer containing molybdenum (Mo) and the high refractive index layer is a layer containing silicon (Si), it can have a mixed region in which Mo and Si are mixed. Such a mixed region can be formed by partially heating the multilayer reflective film 5. For example, the mixed region can be formed by irradiating the multilayer reflective film 5 with laser light and heating it. In this case, the laser beam may be irradiated from above the multilayer reflective film 5, or may be irradiated from above the protective film 6 after forming the protective film 6 on the multilayer reflective film 5. As the light source of the laser light, for example, a CO ₂ laser, a solid-state laser, or the like can be used. The mixed region may be formed by irradiating the multilayer reflective film 5 with an electron beam.

The surface reflectance for EUV light in the mixed region is lower than the surface reflectance for EUV light in the other regions. For example, when a mixed region is formed in the outer peripheral region of the region where the thin film pattern is provided when the reflective mask 200 is manufactured using the substrate 110 with the multilayer reflective film, the multilayer reflective film 5 in the outer peripheral region is formed. The reflectance of the multilayer reflective film 5 can be made lower than the reflectance of the multilayer reflective film 5 in other regions. This makes it possible to prevent unnecessary exposure due to superposition exposure when the reflective mask 200 is set in the exposure apparatus and exposure transfer is performed by step-and-scan. As a result, the pattern can be transferred with high accuracy by the resist film or the like formed on the surface of the semiconductor substrate. The surface reflectance of the mixed region with respect to EUV light is preferably 1.3% or less, more preferably 1% or less, and even more preferably 0.7% or less.

<Reflective mask blank 100>
The reflective mask blank 100 of this embodiment will be described. By using the reflective mask blank 100 of the present embodiment, it is possible to manufacture a reflective mask 200 having a multilayer reflective film 5 having a high reflectance with respect to exposure light.

<< Absorber film (thin film for pattern formation) 7 >>
The reflective mask blank 100 has an absorber film (thin film for pattern formation) 7 on the above-mentioned substrate 110 with a multilayer reflective film. That is, the absorber film 7 is formed on the protective film 6 which is the uppermost layer of the substrate 110 with the multilayer reflective film. The basic function of the absorber film 7 is to absorb EUV light. The absorber film 7 may be an absorber film 7 for the purpose of absorbing EUV light, or may be an absorber film 7 having a phase shift function in consideration of the phase difference of EUV light. The absorber film 7 having a phase shift function absorbs EUV light and reflects a part of the EUV light to shift the phase. That is, in the reflective mask 200 in which the absorber film 7 having a phase shift function is patterned, the portion where the absorber film 7 is formed absorbs EUV light and dims, and the pattern transfer is not adversely affected. Reflects some light. Further, in the region (field portion) where the absorber film 7 is not formed, EUV light is reflected from the multilayer reflective film 5 via the protective film 6. Therefore, a desired phase difference is obtained between the reflected light from the absorber film 7 having the phase shift function and the reflected light from the field portion. The absorber film 7 having a phase shift function is formed so that the phase difference between the reflected light from the absorber film 7 and the reflected light from the multilayer reflective film 5 is 130 degrees to 230 degrees. The image contrast of the projected optical image is improved by the light having the inverted phase difference in the vicinity of 180 degrees interfering with each other at the pattern edge portion. As the image contrast is improved, the resolution is increased, and various exposure-related margins such as exposure amount margin and focal margin can be increased.

The absorber film 7 may be a single-layer film or a multilayer film composed of a plurality of films. In the case of a single-layer film, the number of steps during mask blank manufacturing can be reduced, so that production efficiency is improved. In the case of a multilayer film, the upper absorber film can function as an antireflection film at the time of mask pattern inspection using light. In this case, it is necessary to appropriately set the optical constant and the film thickness of the upper absorber film. As a result, the inspection sensitivity at the time of mask pattern inspection using light is improved. Further, as the upper absorber membrane, a membrane to which oxygen (O), nitrogen (N) or the like, which can improve oxidation resistance, can be used. This improves the stability of the absorber membrane over time. As described above, by using the absorber membrane 7 made of a multilayer film, it is possible to add various functions to the absorber membrane 7. When the absorber film 7 has a phase shift function, the range of adjustment on the optical surface can be increased by using the absorber film 7 made of a multilayer film. This makes it easy to obtain the desired reflectance.

As the material of the absorber film 7, a material that has a function of absorbing EUV light and can be processed by etching or the like (for example, can be etched by dry etching of chlorine (Cl) or fluorine (F) -based gas). Can be used. As a material having such a function, tantalum (Ta) alone or a tantalum compound containing Ta as a main component can be preferably used.

The above-mentioned absorber film 7 such as tantalum and tantalum compound can be formed by a sputtering method such as a DC sputtering method and an RF sputtering method. For example, the absorber film 7 can be formed by a reactive sputtering method using a target containing tantalum and boron and using argon gas to which oxygen or nitrogen is added.

The tantalum compound for forming the absorber film 7 contains an alloy of Ta. When the absorber film 7 is an alloy of Ta, the crystalline state of the absorber film 7 is preferably an amorphous or microcrystalline structure from the viewpoint of smoothness and flatness. If the surface of the absorber film 7 is not smooth or flat, the edge roughness of the absorber pattern 7a may increase and the dimensional accuracy of the pattern may deteriorate. The surface roughness of the absorber film 7 is preferably a root mean square roughness (Rms) of 0.5 nm or less, more preferably 0.4 nm or less, still more preferably 0.3 nm or less.

The tantalum compound for forming the absorber film 7 includes a compound containing Ta and B, a compound containing Ta and N, a compound containing Ta, O and N, Ta and B, and further O. Use a compound containing at least one of N, a compound containing Ta and Si, a compound containing Ta, Si and N, a compound containing Ta and Ge, a compound containing Ta, Ge and N, and the like. Can be done.

Ta has a large EUV light absorption coefficient. Further, Ta is a material that can be easily dry-etched with a chlorine-based gas or a fluorine-based gas. Therefore, it can be said that Ta is a material for the absorber film 7 having excellent processability. Further, by adding B, Si and / or Ge or the like to Ta, an amorphous material can be easily obtained. As a result, the smoothness of the absorber film 7 can be improved. Further, if N and / or O is added to Ta, the resistance of the absorber film 7 to oxidation is improved, so that the stability of the absorber film 7 over time can be improved.

In addition to tantalum or tantalum compounds, the material of the absorber film 7 includes palladium (Pd), silver (Ag), platinum (Pt), gold (Au), yttrium (Ir), tungsten (W), and chromium (W). Cr), cobalt (Co), manganese (Mn), tin (Sn), vanadium (V), nickel (Ni), hafnium (Hf), iron (Fe), copper (Cu), tellurium (Te), zinc ( Zn), magnesium (Mg), germanium (Ge), aluminum (Al), rhodium (Rh), ruthenium (Ru), molybdenum (Mo), niobium (Nb), titanium (Ti), zirconium (Zr), yttrium ( At least one metal selected from Y) and silicon (Si), or compounds thereof can be used.

<< Backside conductive film 2 >>
A back surface conductive film 2 for an electrostatic chuck is formed on the second main surface of the substrate 1 (on the surface opposite to the multilayer reflective film 5). The sheet resistance of the back surface conductive film 2 is usually 100 Ω / □ or less. The back surface conductive film 2 can be formed by, for example, a DC sputtering method, an RF sputtering method, or an ion beam sputtering method using a target of a metal such as chromium or tantalum or an alloy thereof. The material containing chromium (Cr) for forming the back surface conductive film 2 is preferably a Cr compound containing at least one selected from boron, nitrogen, oxygen, and carbon in Cr. Examples of the Cr compound include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN and CrBOCN. The material containing tantalum (Ta) for forming the back surface conductive film 2 is Ta (tantalum), an alloy containing Ta, or at least one of these selected from boron, nitrogen, oxygen, and carbon. It is preferable that it is a Ta compound containing. Examples of the Ta compound include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiN, and TaSiN. can.

The film thickness of the back surface conductive film 2 is not particularly limited, but is usually 10 nm to 200 nm. The back surface conductive film 2 can adjust the stress on the second main surface side of the mask blank 100. That is, the back surface conductive film 2 can balance the stress generated by various films formed on the first main surface side and the stress on the second main surface side. By balancing the stresses on the first main surface side and the second main surface side, the reflective mask blank 100 can be adjusted to be flat.

Before forming the above-mentioned absorber film 7, the back surface conductive film 2 can be formed on the substrate 110 with the multilayer reflective film. In that case, a substrate 110 with a multilayer reflective film having a back surface conductive film 2 as shown in FIG. 1 can be obtained.

<Other thin films>
The substrate 110 with a multilayer reflective film and the reflective mask blank 100 manufactured by the manufacturing method of the present embodiment have a hard mask film for etching (also referred to as “etching mask film”) and / or a resist film on the absorber film 7. 8 can be provided. As a typical material of the hard mask film for etching, silicon (Si) and at least one element selected from oxygen (O), nitrogen (N), carbon (C) and hydrogen (H) are added to silicon. Examples thereof include silicon (Cr) and a material obtained by adding at least one element selected from oxygen (O), nitrogen (N), carbon (C) and hydrogen (H) to silicon. Specific examples thereof include SiO ₂ , SiON, SiN, SiO, Si, SiC, SiCO, SiCN, SiCON, Cr, CrN, CrO, CrON, CrC, CrCO, CrCN, CrOCN and the like. However, when the absorber film 7 is a compound containing oxygen, it is better to avoid a material containing oxygen (for example, SiO ₂ ) as the etching hard mask film from the viewpoint of etching resistance. When the hard mask film for etching is formed, the film thickness of the resist film 8 can be reduced, which is advantageous for the miniaturization of the pattern.

In the reflective mask blank 100 of the present embodiment, the multilayer reflective film 5 can have a mixed region on the first main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed. The mixed region can be formed, for example, by irradiating the multilayer reflective film 5 with laser light and heating it. In this case, the laser beam may be irradiated from above the multilayer reflective film 5, or may be irradiated from above the protective film 6 after forming the protective film 6 on the multilayer reflective film 5. Further, after forming the absorber film 7 on the protective film 6, laser light may be irradiated from above the absorber film 7. As the light source of the laser light, for example, a CO ₂ laser, a solid-state laser, or the like can be used.

The surface reflectance of the mixed region to EUV light is lower than the surface reflectance of the absorber film 7 to EUV light. For example, when a mixed region is formed in the outer peripheral region of the region where the thin film pattern is provided when the reflective mask 200 is manufactured using the reflective mask blank 100, the multilayer reflective film 5 in the outer peripheral region is formed. The reflectance can be made lower than the reflectance of the absorber film 7 in the region where the thin film pattern is provided. This makes it possible to prevent unnecessary exposure due to superposition exposure when the reflective mask 200 is set in the exposure apparatus and exposure transfer is performed by step-and-scan. As a result, the pattern can be transferred with high accuracy by the resist film or the like formed on the surface of the semiconductor substrate.

<Reflective mask 200>
By patterning the absorber film 7 of the above-mentioned reflective mask blank 100, a reflective mask 200 having a protective film 6 on the multilayer reflective film 5 and an absorber pattern 7a on the protective film 6 is obtained. Can be done. By using the reflective mask blank 100 of the present embodiment, it is possible to obtain a reflective mask 200 having a multilayer reflective film 5 having a high reflectance with respect to exposure light.

A method of manufacturing the reflective mask 200 using the reflective mask blank 100 of the present embodiment will be described. Here, only an outline explanation will be given, and later, a detailed explanation will be given with reference to the drawings in the examples.

A reflective mask blank 100 is prepared, and a resist film 8 is formed on the outermost surface of the first main surface thereof (on the absorber film 7 as described in the following examples) (reflective mask blank 100). Is not required if the resist film 8 is provided). A desired pattern such as a circuit pattern was drawn (exposed) on the resist film 8. At this time, in the subsequent step, when performing a process of forming a mixed region on the multilayer reflective film 5 of the region 204 on the outer periphery of the region where the thin film pattern to be the transfer pattern is provided (processing by laser irradiation, electron beam irradiation, etc.), The pattern of the area 204 on the outer periphery may also be drawn (exposed). Further, the resist film 8 is developed and rinsed to form a predetermined resist pattern 8a.

Using this resist pattern 8a as a mask, the absorber film 7 is dry-etched to form the absorber pattern 7a. The etching gas includes chlorine-based gas such as Cl ₂ , SiCl ₄ , and CHCl ₃ , mixed gas containing chlorine-based gas and O ₂ in a predetermined ratio, and chlorine-based gas and He in a predetermined ratio. Mixed gas containing, mixed gas containing chlorine gas and Ar in a predetermined ratio, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , A gas selected from a fluorine-based gas such as CH ₃ F, C ₃ F ₈ , SF ₆ , F ₂ and a mixed gas containing a fluorine-based gas and O ₂ in a predetermined ratio can be used.

Next, the reflective mask 200 can be manufactured by removing the resist pattern 8a with an ashing or a resist stripping solution.

In the reflective mask 200 of the present embodiment, the multilayer reflective film 5 can have a mixed region on the first main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed. The mixed region can be formed, for example, by irradiating the multilayer reflective film 5 with laser light and heating it. In this case, the laser beam may be irradiated from above the multilayer reflective film 5, or may be irradiated from above the protective film 6 after forming the protective film 6 on the multilayer reflective film 5. Further, after forming the absorber film 7 on the protective film 6, laser light may be irradiated from above the absorber film 7. Further, after forming the absorber pattern 7a on the absorber film 7, laser light may be irradiated from above the absorber film 7 in the outer peripheral region of the region where the absorber pattern 7a is formed. As the light source of the laser light, for example, a CO ₂ laser, a solid-state laser, or the like can be used.

The surface reflectance of the mixed region to EUV light is lower than the surface reflectance of the absorber pattern 7a to EUV light. For example, when a mixed region is formed in the outer peripheral region of the region provided with the absorber pattern 7a, the reflectance of the multilayer reflective film 5 in the outer peripheral region is made lower than the reflectance of the absorber pattern 7a. be able to. This makes it possible to prevent unnecessary exposure due to superposition exposure when the reflective mask 200 is set in the exposure apparatus and exposure transfer is performed by step-and-scan. As a result, the pattern can be transferred with high accuracy by the resist film or the like formed on the surface of the semiconductor substrate.

On the other hand, in the substrate 110 with a multilayer reflective film, the reflective mask blank 100, and the reflective mask 200, a reference mark may be formed on the multilayer reflective film 5. Generally, when a defect is present on the first main surface of the substrate 1, the multilayer reflective film 5, the protective film 6, the absorber film 7, or the like, this reference mark is provided to serve as a reference for the position coordinates of the defect. When the protective film 6 and the multilayer reflective film 5 are irradiated with high-energy light such as laser light to shrink the protective film 6 and the multilayer reflective film 5 to form a recess, and this recess is used as a reference mark. There is. When the reference mark is formed by such a method, a phenomenon occurs in which hydrogen and OH groups incorporated in the multilayer reflective film 5 are vaporized and accumulated between the multilayer reflective film 5 and the protective film 6. Further, a phenomenon that the protective film 6 on the multilayer reflective film 5 swells and a phenomenon that the protective film 6 itself bursts occurs. By applying the above-mentioned multilayer reflective film 5, it is possible to form a reference mark without causing these phenomena.

<Manufacturing method of semiconductor device>
The method for manufacturing a semiconductor device of the present embodiment includes a step of performing a lithography process using an exposure apparatus using the above-mentioned reflective mask 200 to expose and transfer a transfer pattern to a transfer target.

By performing EUV exposure using the reflective mask 200 of the present embodiment, a desired transfer pattern can be exposed and transferred to a resist film on a semiconductor substrate. In addition to this lithography process, various processes such as etching of the film to be processed, forming of insulating film, conductive film, introduction of dopant, and annealing are performed to manufacture a semiconductor device in which a desired electronic circuit is formed with a high yield. can do.

Hereinafter, Examples and Comparative Examples will be described with reference to the drawings.
As shown in FIG. 1, the substrate 110 with a multilayer reflective film of the embodiment has a substrate 1, a multilayer reflective film 5, and a protective film 6.

First, four 6025 size (about 152 mm × 152 mm × 6.35 mm) substrates 1 were prepared, which were cut out from SiO ₂ -TiO ₂ glass ingots having different configurations and the first main surface and the second main surface were polished. .. These substrates 1 are substrates made of low thermal expansion glass (SiO ₂ -TIO ₂ system glass). The main surface of the substrate 1 was polished by a rough polishing process, a precision polishing process, a local processing process, and a touch polishing process.

Next, the multilayer reflective film 5 was formed on the main surface (first main surface) of the four substrates 1. The multilayer reflective film 5 formed on the substrate 1 is a periodic multilayer reflective film 5 composed of Mo and Si in order to make the multilayer reflective film 5 suitable for EUV light having a wavelength of 13.5 nm. The multilayer reflective film 5 was formed by alternately laminating Mo film and Si film on the substrate 1 by an ion beam sputtering method using an atmosphere of Kr gas using a Mo target and a Si target. First, a Si film was formed with a thickness of 4.2 nm, and then a Mo film was formed with a thickness of 2.8 nm. This was set as one cycle, and the layers were laminated for 40 cycles in the same manner, and finally a Si film was formed with a thickness of 4.0 nm to form a multilayer reflective film 5.

Next, the substrate 1 after the four multilayer reflective films 5 were formed was heat-treated with a hot plate to reduce the film stress of the multilayer reflective film 5. Table 1 shows the conditions of each heat treatment (heating temperature is 200 ° C.).

Next, a protective film 6 made of a material containing Ru was formed on the multilayer reflective film 5 of the four substrates 1. The protective film 6 was formed with a film thickness of 2.5 nm by a DC sputtering method using a Ru target in an Ar gas atmosphere. Through the above steps, four substrates 110 with a multilayer reflective film were manufactured.

<< Hydrogen Atomic Density in Multilayer Reflective Film 5 >>
The atomic number density [atoms / nm ³ ] of hydrogen contained in the multilayer reflective film 5 of the substrate 110 with the four multilayer reflective films manufactured as described above is determined by SIMS (quadrupole secondary ion mass spectrometer: Measured by PHI ADEPT-1010 ^TM , manufactured by ULVAC PHI Co., Ltd.). The measurement conditions are Cs ⁺ for the primary ion species, 1.0 kV for the primary acceleration voltage, 90 μm square for the primary ion irradiation region, positive for the secondary ion polarity, and [Cs-H] ⁺ and [Cs-] for the detected secondary ion species. It was set as D] ⁺ or [Cs-He] ⁺ . The standard sample was Si. The measurement results are shown in Table 1 below.

<< Hydrogen atom density in substrate 1 >>
The atomic number density [atoms / cm ³ ] of hydrogen in the substrate 1 of the substrate 110 with the above four multilayer reflective films is measured by SIMS (quadrupole secondary ion mass spectrometry) in the same procedure as in the case of the multilayer reflective film 5. Device: PHI ADEPT-1010 ^TM , manufactured by ULVAC PFI Co., Ltd.). The measurement results are shown in Table 1.

<Reflective mask blank 100>
Next, an absorber film 7 made of a material containing TaBN was formed on the protective film 6 of the substrate 110 with four multilayer reflective films. The absorber film 7 was formed into a film having a film thickness of 62 nm by a DC sputtering method using a TaB mixed sintering target in a mixed gas atmosphere of Ar gas and N ₂ gas.

The element ratio of the TaBN film was 75 atomic% for Ta, 12 atomic% for B, and 13 atomic% for N. The refractive index n of the TaBN film at a wavelength of 13.5 nm was about 0.949, and the extinction coefficient k was about 0.030.

Next, a back surface conductive film 2 made of CrN was formed on the second main surface (back surface) of the four multilayer reflective film-equipped substrates 110 by a DC sputtering (reactive sputtering) method under the following conditions.
Conditions for forming the back surface conductive film 2: Cr target, mixed gas atmosphere of Ar and N ₂ (Ar: 90 atomic%, N: 10 atomic%), film thickness 20 nm.

As described above, four reflective mask blanks 100 having the absorber film 7 on the protective film 6 were manufactured.

<Reflective mask 200>
Next, the reflective mask 200 was manufactured by using the above-mentioned four reflective mask blanks 100. A method for manufacturing each reflective mask 200 will be described with reference to FIG.

First, as shown in FIG. 3B, a resist film 8 was formed on the absorber film 7 of the reflective mask blank 100. Next, a desired pattern such as a circuit pattern was drawn (exposed) on the resist film 8. At this time, the pattern of the outer peripheral region 204 that irradiates the multilayer reflective film 5 with the laser beam in the subsequent step is also drawn (exposed). Next, a predetermined resist pattern 8a was formed by developing and rinsing the resist film 8 (FIG. 3 (c)). Next, the absorber film 7 (TaBN film) was dry-etched with Cl ₂ gas using the resist pattern 8a as a mask to form the absorber pattern 7a (FIG. 3 (d)). The protective film 6 made of a material containing Ru has extremely high dry etching resistance to Cl ₂ gas, and is a sufficient etching stopper. Then, the resist pattern 8a was removed by ashing, a resist stripping solution, or the like. Next, the multilayer reflective film 5 in the outer peripheral region 204 from which the absorber film 7 is removed is subjected to a treatment of irradiating the protective film 6 with CO ₂ laser light, and the low refractive index layer of the multilayer reflective film 5 is applied. A mixed region was formed by mixing the constituent element (Mo) of the above and the constituent element (Si) of the high refractive index layer. By the above steps, four reflective masks 200 were manufactured (FIG. 3 (e)).

The four reflective masks 200 manufactured as described above have a 132 mm × 132 mm region 202 provided with an absorber pattern 7a (thin film pattern) on the first main surface, and an outer peripheral region of the region 202. Has 204. The outer peripheral region 204 is a region in which the absorber pattern 7a is not provided, and the multilayer reflective film 5 in that region includes a constituent element (Mo) of the low refractive index layer and a constituent element (Si) of the high refractive index layer. A mixed region is formed. The reflectance of the multilayer reflective film 5 (with the protective film 6 laminated on it) in the outer peripheral region 204 of the four reflective masks 200 was measured and found to be 0 for EUV light having a wavelength of 13.5 nm. It was 0.7% or less. Further, when the reflectance of the four reflective masks 200 to EUV light having a wavelength of 13.5 nm in the region 202 provided with the absorber pattern 7a was measured, all of them were 67% or more.

As can be seen from the results shown in Table 1, the reflectance of the multilayer reflective film 5 in the outer peripheral region 204 was sufficiently lower than the reflectance of the absorber pattern 7a in the region where the pattern was formed (region 202).

As a result of observing the cross section of the reflective mask 200 with an electron microscope, no swelling or peeling was observed between the multilayer reflective film and the protective film in the reflective masks of Examples 1 to 3. In addition, no phenomenon such as rupture of the protective film itself was observed.

On the other hand, in the reflective mask of Comparative Example 1, it was confirmed that hydrogen was accumulated between the multilayer reflective film and the protective film to cause swelling. It was also confirmed that the protective film itself ruptured.

1 Substrate 2 Backside conductive film 5 Multilayer reflective film 6 Protective film 7 Absorber film 7a Absorber pattern 8 Resist film 8a Resist pattern 100 Reflective mask blank 110 Substrate with multilayer reflective film 200 Reflective mask

Claims (15)

A substrate with a multilayer reflective film having a multilayer reflective film and a protective film in this order on the main surface of the substrate.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less. The substrate with a multilayer reflective film according to claim 1, wherein the high refractive index layer contains silicon, and the low refractive index layer contains molybdenum. The claim is characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by secondary ion mass spectrometry is 1.0 × 10 ¹⁹ atoms / cm ³ or more. The substrate with a multilayer reflective film according to 1 or 2. The substrate with a multilayer reflective film according to any one of claims 1 to 3, wherein the protective film contains ruthenium. The multilayer reflective film has a mixed region on the main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed, and the surface reflectance of the mixed region with respect to EUV light is the same. The substrate with a multilayer reflective film according to any one of claims 1 to 4, which has a lower surface reflectance than the surface reflectance for EUV light in a region other than the above. A mask blank in which a multilayer reflective film, a protective film, and a thin film for pattern formation are provided in this order on the main surface of the substrate.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less. The mask blank according to claim 6, wherein the high refractive index layer contains silicon, and the low refractive index layer contains molybdenum. The claim is characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by a secondary ion mass spectrometry method is 1.0 × 10 ¹⁹ atoms / cm ³ or more. The mask blank according to 6 or 7. The mask blank according to any one of claims 6 to 8, wherein the protective film contains ruthenium. The multilayer reflective film has a mixed region on the main surface in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed, and the surface reflectance of the mixed region with respect to EUV light is the above. The mask blank according to any one of claims 6 to 9, wherein the pattern-forming thin film has a lower surface reflectance to EUV light. A reflective mask having a multilayer reflective film, a protective film, and a thin film pattern on the main surface of the substrate in this order.
The substrate contains silicon, titanium and oxygen as main components, and further contains hydrogen.
The multilayer reflective film has a structure in which low refractive index layers and high refractive index layers are alternately laminated.
The multilayer reflective film contains hydrogen, and the atomic number density of hydrogen in the multilayer reflective film is 7.0 × 10 ^-3 atoms / nm ³ or less.
The multilayer reflective film has a mixed region in which the constituent elements of the low refractive index layer and the constituent elements of the high refractive index layer are mixed in the outer peripheral region of the region where the thin film pattern is provided on the main surface. A reflective mask characterized in that the surface reflectance of the mixed region to EUV light is lower than the surface reflectance of the thin film pattern to EUV light. The reflective mask according to claim 11, wherein the high refractive index layer contains silicon, and the low refractive index layer contains molybdenum. The claim is characterized in that the atomic number density of hydrogen in the substrate obtained by analyzing the substrate by a secondary ion mass spectrometry method is 1.0 × 10 ¹⁹ atoms / cm ³ or more. 11. The reflective mask according to 11. The reflective mask according to any one of claims 11 to 13, wherein the protective film contains ruthenium. A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the reflective mask according to any one of claims 11 to 14.

Images