JP5333016B2 - Reflective mask blank for EUV lithography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective mask blank for EUV lithography having a low reflecting layer which has a low reflectivity in the wavelength band of EUV light and inspection light of a mask pattern, having especially low reflection characteristic in the entire wavelength band (190-260 nm) of the inspection light of mask pattern, while keeping excellent adhesion to a resist. <P>SOLUTION: In the reflective mask blank for EUV lithography, a reflecting layer for reflecting EUV light, an absorber layer for absorbing EUV light, and a low reflecting layer for the inspection light (wavelength 190-260 nm) of mask pattern are formed on a substrate in this order. The reflective mask blank for EUV lithography is characterized in that the low reflecting layer contains at least one of aluminum (Al) and zirconium (Zr) as well as at least one of oxygen (O) and nitrogen (N). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a reflective mask blank (hereinafter referred to as “EUV mask blank”) for EUV (Extreme Ultra Violet) lithography used in semiconductor manufacturing and the like.

  2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a Si substrate or the like. However, while miniaturization of semiconductor devices is accelerating, the limits of conventional photolithography methods have been approached. In the case of the photolithography method, the resolution limit of the pattern is about ½ of the exposure wavelength, and it is said that the immersion wavelength is about ¼ of the exposure wavelength, and the immersion of ArF laser (193 nm) is used. Even if the method is used, the limit of about 45 nm is expected. Therefore, EUV lithography, which is an exposure technique using EUV light having a wavelength shorter than that of an ArF laser, is promising as an exposure technique for 45 nm and beyond. In this specification, EUV light refers to light having a wavelength in the soft X-ray region or vacuum ultraviolet region, and specifically refers to light having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ± 0.3 nm.

  Since EUV light is easily absorbed by any material and the refractive index of the material is close to 1 at this wavelength, a conventional refractive optical system such as photolithography using visible light or ultraviolet light may be used. Can not. For this reason, in the EUV light lithography, a reflective optical system, that is, a reflective photomask and a mirror are used.

  The mask blank is a laminated body before patterning used for photomask manufacturing. In the case of an EUV mask blank, a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate such as glass. As the reflective layer, a multilayer reflective film is generally used in which a high refractive layer and a low refractive layer are alternately laminated to increase the light reflectivity when EUV light is irradiated onto the layer surface. For the absorber layer, a material having a high absorption coefficient with respect to EUV light, specifically, for example, a material mainly composed of Ta or Cr is often used.

  On the absorber layer of the EUV mask blank, a low reflection layer for mask pattern inspection light is usually provided. For the presence or absence of pattern defects after mask pattern formation, light in the wavelength range of deep ultraviolet light (190 to 260 nm) is often used. In the pattern inspection using the light beam in the above wavelength range, the reflectance difference between the region where the low reflection layer and the absorber layer are removed by the patterning process and the region where the low reflection layer and the absorber layer remain, that is, The presence or absence of pattern defects is inspected by the contrast of reflected light on the surfaces of these regions. In order to improve the inspection sensitivity of the mask pattern, it is necessary to increase the contrast. For this purpose, the low reflection layer has low reflection characteristics with respect to the above wavelength range, that is, with respect to the above wavelength range. The reflectivity is required to be 15% or less.

In Patent Document 1, a low reflective layer made of a tantalum boron alloy oxide (TaBO) or a tantalum boron alloy oxynitride (TaBNO) is formed on an absorber layer made of a tantalum boron alloy nitride (TaBN). This is preferable because the reflectance of the mask pattern with respect to the wavelength range (190 nm to 260 nm) of the inspection light is low.
In Patent Documents 2 and 3, metal, silicon (Si), oxygen (O), and nitrogen are formed on the absorber layer in order to adjust the reflectance of the mask pattern with respect to the wavelength range (190 nm to 260 nm) of the inspection light. It is preferable to provide a low reflection layer made of (N).

Japanese Patent Laid-Open No. 2004-6798 JP 2006-228767 A JP 2008-70799 A

As the mask pattern becomes finer, it is predicted that the wavelength of the pattern inspection light will be shortened in the future, and the most influential wavelength range is 190 to 200 nm. In Patent Document 1, when the low reflection layer is a TaBO film or a TaBNO film, a sufficient contrast is obtained for the wavelength 257 nm of the inspection light of the mask pattern currently used. In respect of (190-200 nm), it is not shown at all whether these films exhibit low reflection characteristics.
In Patent Document 2, the oxygen concentration, nitrogen concentration, and film thickness of a material (for example, TaSiON, ZrSiON, etc.) made of metal, silicon (Si), oxygen (O), and nitrogen (N) are adjusted as the low reflection layer. This makes it possible to obtain low reflection characteristics for the mask pattern inspection light wavelength of 257 nm that is currently used and the mask pattern inspection light wavelength of 193 nm that is expected to be used in the future. Yes. However, in the case of a film containing silicon (Si) as described above, there is a concern that there may be a problem in adhesion with a mask pattern resist as described in paragraph [0003] of Patent Document 3. . Patent Document 3 describes the adhesiveness between a silicon-containing film and a resist applied when forming a pattern. In the case of a film containing silicon, it is described that the adhesiveness with the resist is not sufficient. Yes. That is, when the low reflective layer is a silicon-containing film, the adhesiveness with the resist applied at the time of forming the mask pattern is not sufficient, and problems such as disappearance of the resist pattern and defects in the resist pattern may occur.

  In order to solve the above-described problems of the prior art, the present invention is excellent in characteristics as an EUV mask blank, and further has a wavelength region (190 to 260 nm) of pattern inspection light, particularly pattern inspection light that is expected to be used in the future. It is an object of the present invention to provide an EUV mask blank having a low reflection layer having a low reflectance in the wavelength region (190 to 200 nm) and good adhesion to a resist.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the low-reflection layer a film containing a combination of specific elements, so that the wavelength range (190 to 260 nm) of the inspection light of the mask pattern The present inventors have found that it has a low reflection layer characteristic and has sufficient adhesion to a resist.

The present invention has been made on the basis of the above findings, and on a substrate, a reflective layer that reflects EUV light, an absorber layer that absorbs EUV light, and mask pattern inspection light (wavelength 190 nm to 260 nm). A reflective mask blank for EUV lithography formed in this order,
The reflective mask for EUV lithography, wherein the low reflective layer contains at least one of aluminum (Al) and zirconium (Zr) and at least one of oxygen (O) and nitrogen (N) A blank (hereinafter referred to as “EUV mask blank of the present invention”) is provided.

  In the EUV mask blank of the present invention, the total content of Al and Zr is 20 to 70 at%, the total content of O and N is 30 to 80 at%, and the total content of Al, Zr, O and N Is preferably 95 to 100 at%.

In the EUV mask blank of the present invention, the surface roughness (rms) of the surface of the low reflective layer is preferably 0.5 nm or less.
In the EUV mask blank of the present invention, it is preferable that the crystal structure of the surface of the low reflective layer is amorphous.
In the EUV mask blank of the present invention, the low reflective layer preferably has a thickness of 3 to 30 nm.

In the EUV mask blank of the present invention, the absorber layer is preferably an absorber layer containing tantalum (Ta) as a main component.
In the EUV mask blank of the present invention, the absorber layer contains tantalum (Ta) as a main component, hafnium (Hf), silicon (Si), zirconium (Zr), germanium (Ge), boron (B), nitrogen ( N) and at least one element selected from hydrogen (H) may be included.
In the EUV mask blank of the present invention, the absorber layer preferably has an oxygen (O) content of less than 25 at%.
In the EUV mask blank of the present invention, the total film thickness of the absorber layer and the low reflection layer is preferably 40 to 200 nm.

Further, in the EUV mask blank of the present invention, a protective layer for protecting the reflective layer is formed between the reflective layer and the absorber layer when forming a pattern on the absorber layer,
It is preferable that the contrast represented by the following formula is 60% or more.
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
(Where R ₂ is the reflectance on the surface of the protective layer with respect to the wavelength of the inspection light of the mask pattern (190 nm to 260 nm), and R ₁ is the surface of the low reflection layer with respect to the wavelength of the inspection light of the mask pattern (190 nm to 260 nm)) The reflectance at.
In the EUV mask blank of the present invention, when a protective layer is formed between the reflective layer and the absorber layer, the protective layer is formed of any one of Ru, Ru compound, SiO ₂ and CrN. It is preferable.

  In the EUV mask blank of the present invention, the reflectance of the low reflective layer surface with respect to the wavelength (190 to 260 nm) of the inspection light of the mask pattern is preferably 15% or less.

  In the EUV mask blank of the present invention, the low reflective layer includes an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), oxygen ( It is preferably formed by performing a sputtering method using a target including at least one of Al and Zr in an atmosphere including at least one of O) and nitrogen (N).

Further, according to the present invention, a reflective layer that reflects EUV light, an absorber layer that absorbs EUV light, and a low reflective layer for mask pattern inspection light (wavelength 190 to 260 nm) are formed in this order on the substrate. A method of manufacturing an EUV mask blank by:
The low reflective layer includes an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), oxygen (O), and nitrogen (N). The present invention provides a method for producing an EUV mask blank, which is formed by performing a sputtering method using a target containing at least one of Al and Zr in an atmosphere containing at least one of the above.

  The present invention also provides a reflective mask for EUV lithography (hereinafter referred to as “the EUV mask of the present invention”) in which the absorber layer and the low reflective layer of the EUV mask blank of the present invention are patterned.

  The present invention also provides a semiconductor integrated circuit manufacturing method for manufacturing a semiconductor integrated circuit by exposing an object to be exposed using the EUV mask described above.

  The EUV mask blank of the present invention uses a film containing at least one of aluminum (Al) or zirconium (Zr) and at least one of oxygen (O) and nitrogen (N) in the low reflection layer. The reflectance in the wavelength region of pattern inspection light (190 to 260 nm), particularly the wavelength region of pattern inspection light (190 to 200 nm) that is expected to be used in the future, is low, and the adhesiveness to the resist is good. As a result, pattern inspection with high sensitivity is possible even for finer patterns, and it is expected that problems such as resist disappearance and resist pattern defects will not occur.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. FIG. 2 shows a state where the absorber layer 14 and the low reflection layer 15 of the EUV mask blank 1 shown in FIG. 1 are patterned.

Hereinafter, the EUV mask blank of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. In the mask blank 1 shown in FIG. 1, a reflective layer 12 that reflects EUV light and an absorber layer 14 that absorbs EUV light are formed on a substrate 11 in this order. A protective layer 13 is formed between the reflective layer 12 and the absorber layer 14 to protect the reflective layer 12 when forming a pattern on the absorber layer 14. On the absorber layer 14, a low reflection layer 15 for the inspection light of the mask pattern is formed. However, in the EUV mask blank 1 of the present invention, only the substrate 11, the reflective layer 12, the absorber layer 14, and the low reflective layer 15 are essential in the configuration shown in FIG. 1, and the protective layer 13 is an optional component. .
Hereinafter, individual components of the mask blank 1 will be described.

The substrate 11 is required to satisfy the characteristics as a substrate for an EUV mask blank.
Therefore, the substrate 11, the low thermal expansion coefficient (specifically, it is preferable that the thermal expansion coefficient at 20 ° C. is ^{0 ± 0.05 × 10 -7 / ℃} , particularly preferably 0 ± 0.03 × 10 ^{- 7} / ° C.) and excellent in smoothness, flatness, and resistance to a cleaning liquid used for cleaning a mask blank or a photomask after pattern formation. Specifically, the substrate 11 is made of glass having a low thermal expansion coefficient, such as SiO ₂ —TiO ₂ glass, but is not limited thereto, and is not limited to crystallized glass, quartz glass, silicon, A substrate made of metal or the like can also be used.
The substrate 11 preferably has a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less in order to obtain high reflectivity and transfer accuracy in a photomask after pattern formation. .
The size, thickness, etc. of the substrate 11 are appropriately determined by the design value of the mask. In an example described later, SiO ₂ —TiO ₂ glass having an outer shape of about 6 inches (152 mm) square and a thickness of about 0.25 inches (6.3 mm) was used.
It is preferable that the surface of the substrate 11 on the side where the reflective layer 12 is formed has no defects. However, even if it exists, the depth of the concave defect and the height of the convex defect are not more than 2 nm so that the phase defect does not occur due to the concave defect and / or the convex defect. It is preferable that the half width of the defect and the convex defect is 60 nm or less.

  The reflective layer 12 is not particularly limited as long as it has desired characteristics as a reflective layer of an EUV mask blank. Here, the characteristic particularly required for the reflective layer 12 is a high EUV light reflectance. Specifically, when the surface of the reflective layer 12 is irradiated with light in the wavelength region of EUV light at an incident angle of 6 degrees, the maximum value of light reflectance near a wavelength of 13.5 nm is preferably 60% or more, More preferably, it is 65% or more. Even when the protective layer 13 and the low reflective layer 15 are provided on the reflective layer 12, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, and 65% or more. It is more preferable that

  Since the reflective layer 12 can achieve a high EUV light reflectance, a multilayer reflective film in which a high refractive layer and a low refractive index layer are alternately laminated a plurality of times is usually used as the reflective layer 12. In the multilayer reflective film forming the reflective layer 12, Mo is widely used for the high refractive index layer, and Si is widely used for the low refractive index layer. That is, the Mo / Si multilayer reflective film is the most common. However, the multilayer reflective film is not limited to this, and Ru / Si multilayer reflective film, Mo / Be multilayer reflective film, Mo compound / Si compound multilayer reflective film, Si / Mo / Ru multilayer reflective film, Si / Mo / Ru / A Mo multilayer reflective film and a Si / Ru / Mo / Ru multilayer reflective film can also be used.

  The thickness of each layer constituting the multilayer reflective film constituting the reflective layer 12 and the number of repeating units of the layers can be appropriately selected according to the film material used and the EUV light reflectance required for the reflective layer. Taking the Mo / Si reflective film as an example, in order to obtain the reflective layer 12 having a maximum EUV light reflectance of 60% or more, the multilayer reflective film is composed of a Mo layer having a film thickness of 2.3 ± 0.1 nm, A Si layer having a thickness of 4.5 ± 0.1 nm may be laminated so that the number of repeating units is 30 to 60.

In addition, what is necessary is just to form each layer which comprises the multilayer reflective film which comprises the reflective layer 12 so that it may become desired thickness using well-known film-forming methods, such as a magnetron sputtering method and an ion beam sputtering method. For example, when an Si / Mo multilayer reflective film is formed by ion beam sputtering, an Si target is used as a target, and Ar gas (gas pressure 1.3 × 10 ⁻² Pa to 2.7 × 10 ⁻ is used as a sputtering gas. ² Pa), an Si film is formed to have a thickness of 4.5 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 0.03 to 0.3 nm / sec. using a target, using an Ar gas (gas pressure ^{1.3 × 10 -2 Pa~2.7 × 10 -2} Pa), an ion acceleration voltage 300 to 1,500 V, the deposition rate of 0.03 to 0 It is preferable to form the Mo film so that the thickness is 2.3 nm at a rate of 3 nm / sec. With this as one period, the Si / Mo multilayer reflective film is formed by laminating the Si film and the Mo film for 40 to 50 periods.

  In order to prevent the surface of the reflective layer 12 from being oxidized, it is preferable that the uppermost layer of the multilayer reflective film forming the reflective layer 12 is a layer made of a material that is difficult to be oxidized. The layer of material that is not easily oxidized functions as a cap layer of the reflective layer 12. As a specific example of the layer of a material that hardly functions to be oxidized and functions as a cap layer, a Si layer can be exemplified. When the multilayer reflective film forming the reflective layer 12 is an Si / Mo film, the uppermost layer can be made to function as a cap layer by making the uppermost layer an Si layer. In that case, the thickness of the cap layer is preferably 9 to 13 nm.

The protective layer 13 is provided for the purpose of protecting the reflective layer 12 so that the reflective layer 12 is not damaged by the etching process when the absorber layer 14 is patterned by an etching process, usually a dry etching process. . Therefore, as the material of the protective layer 13, a material that is not easily affected by the etching process of the absorber layer 14, that is, the etching rate is slower than that of the absorber layer 14 and is not easily damaged by the etching process is selected. Examples of the material satisfying this condition include Cr, Al, Ta and nitrides thereof, Ru and Ru compounds (RuB, RuSi, etc.), and SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ and mixtures thereof. Is done. Among these, Ru and Ru compounds (RuB, RuSi, etc.), CrN and SiO ₂ are preferable, and Ru and Ru compounds (RuB, RuSi, etc.) are particularly preferable.
The thickness of the protective layer 13 is preferably 1 to 60 nm.

The protective layer 13 is formed using a known film formation method such as magnetron sputtering or ion beam sputtering. When a Ru film is formed by magnetron sputtering, a Ru target is used as a target, Ar gas (gas pressure 1 × 10 ⁻² Pa to 10 × 10 ⁻¹ Pa) is used as a sputtering gas, and input power is 30 to 1500 V. It is preferable to form the film at a film formation rate of 0.02 to 1 nm / sec and a thickness of 2 to 5 nm.

The characteristic particularly required for the absorber layer 14 is that the EUV light reflectance is extremely low. Specifically, when the surface of the absorber layer 14 is irradiated with light in the wavelength region of EUV light, the maximum light reflectance near a wavelength of 13.5 nm is 5% or less, particularly 3% or less, more preferably 1% or less. Preferably there is.
In the EUV mask blank 1 of the present invention, even when the surface of the low reflection layer 15 is irradiated with light in the wavelength region of EUV light, the maximum light reflectance near a wavelength of 13.5 nm is 5% or less, particularly 3% or less. Further, it is preferably 1% or less.

In order to achieve the above characteristics, the absorber layer 14 is made of a material having a high EUV light absorption coefficient. As a material having a high EUV light absorption coefficient, a material mainly composed of tantalum (Ta) is preferably used. In this specification, a material containing tantalum (Ta) as a main component means a material containing Ta in the material at 40 at% or more, preferably 50 at% or more, more preferably 55 at% or more.
The material mainly composed of Ta used for the absorber layer 14 is selected from hafnium (Hf), silicon (Si), zirconium (Zr), germanium (Ge), boron (B) and nitrogen (N) in addition to Ta. It may contain at least one element. Specific examples of the material containing the above elements other than Ta include TaN, TaHf, TaHfN, TaBSi, TaBSiN, TaB, TaBN, TaSi, TaSiN, TaGe, TaGeN, TaZr, TaZrN, and the like.

  However, it is preferable that the absorber layer 14 does not contain oxygen (O). Specifically, the O content in the absorber layer 14 is preferably less than 25 at%. When forming a pattern on the absorber layer 14, a dry etching process is usually used, and a chlorine-based gas or a fluorine-based gas is usually used as an etching gas. When a film containing Ru or a Ru compound is formed as a protective layer on the reflective layer for the purpose of preventing the reflective layer from being damaged by the etching process, the protective layer is less damaged, so that it is mainly used as an etching gas. Chlorine-based gas is used. However, when the dry etching process is performed using a chlorine-based gas, if the absorber layer 14 contains oxygen, the etching rate is lowered, and resist damage is increased, which is not preferable. The oxygen content in the absorber layer 14 is preferably 15 at% or less, more preferably 10 at% or less, and further preferably 5 at% or less. Furthermore, the oxygen content of the low reflection layer and the absorption layer described later is more preferably 10 at% or less, and particularly preferably 5 at% or less.

  The absorber layer 14 is preferably set so that the total thickness of the absorber layer 14 and the low reflective layer 15 is 40 to 200 nm, and the total thickness of both is 50 to 200 nm. It is more preferable to set the film thickness. It is more preferable to set the film thickness so that the total film thickness of both is 50 to 150 nm, and it is particularly preferable to set the film thickness to be 50 to 100 nm.

The absorber layer 14 having the above-described configuration can be formed by performing a known film forming method, for example, a magnetron sputtering method or an ion beam sputtering method.
For example, when a TaHf film is formed as the absorber layer 14 by using a magnetron sputtering method, it may be performed under the following conditions.
Sputtering target: TaHf compound target (Ta = 30 to 70 at%, Hf = 70 to 30 at%)
Sputtering gas: an inert gas such as Ar gas (gas pressure ^{1 × 10 -1 Pa~50 × 10 -1} Pa, preferably ^{1 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1 × 10 ^{- 1} Pa to 30 × 10 ⁻¹ Pa)
Vacuum degree before film formation: 1 × 10 ⁻⁴ Pa or less, preferably 1 × 10 ⁻⁵ Pa or less, more preferably 10 ⁻⁶ Pa or less Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500W
Deposition rate: 2 to 60 nm / min, preferably 3.5 to 45 nm / min, more preferably 5 to 30 nm / min
Moreover, what is necessary is just to implement on the following conditions, when forming a TaN layer as the absorber layer 14 using a magnetron sputtering method.
Sputtering target: Ta target Sputtering gas: N ₂ gas (gas pressure ^{1 × 10 -1 Pa~50 × 10 -1} Pa diluted with an inert gas such as Ar gas, preferably 1 × 10 ^-1 Pa~40 × 10 ^-1 Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Vacuum degree before film formation: 1 × 10 ⁻⁴ Pa or less, preferably 1 × 10 ⁻⁵ Pa or less, more preferably 10 ⁻⁶ Pa or less Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500W
Deposition rate: 2 to 60 nm / min, preferably 3.5 to 45 nm / min, more preferably 5 to 30 nm / min

  The low reflection layer 15 is composed of a film exhibiting low reflection characteristics with respect to the wavelength of inspection light used for inspection of the mask pattern. When producing an EUV mask, after forming a pattern in an absorber layer, it is inspected whether this pattern is formed as designed. In the inspection of the mask pattern, an inspection machine using light of about 257 nm is currently used as inspection light. However, as the pattern width becomes smaller, the wavelength used for the inspection light becomes shorter, and it is predicted that wavelengths of 190 to 199 nm will be used in the future. That is, the difference in reflectance with respect to the inspection light having such a wavelength, specifically, the surface where the absorber layer 14 is removed by pattern formation and the surface of the absorber layer 14 that remains without being removed by pattern formation. And the difference in reflectivity, that is, the contrast of reflected light on these surfaces. Here, the former is the surface of the reflective layer 12. However, when the protective layer 13 is formed on the reflective layer 12, it is the surface of the protective layer 13. Therefore, if the difference in reflectance between the surface of the reflective layer 12 or the protective layer 13 and the surface of the absorber layer 14 with respect to the wavelength of the inspection light is small, the contrast at the time of inspection deteriorates and accurate inspection cannot be performed. .

  The absorber layer 14 having the above-described configuration has extremely low EUV light reflectance, and has excellent characteristics as the absorber layer of the EUV mask blank 1, but when viewed with respect to the wavelength of inspection light, the light reflectance is low. It is not necessarily low enough. As a result, the difference between the reflectance on the surface of the absorber layer 14 and the reflectance on the surface of the protective layer 13 with respect to the wavelength of the inspection light becomes small, and there is a possibility that sufficient contrast at the time of inspection cannot be obtained. If sufficient contrast at the time of inspection is not obtained, pattern defects cannot be sufficiently determined in the inspection of the mask pattern, and accurate defect inspection cannot be performed.

In the EUV mask blank 1 of the present invention, by forming the low reflection layer 15 for the inspection light of the mask pattern on the absorber layer 14, the contrast at the time of inspection becomes good. In the case of the EUV mask blank 1 of the present invention, the contrast of the reflected light is the difference in reflectance between the surface of the reflective layer 12 and the surface of the low reflective layer 15 with respect to the wavelength of the inspection light. However, when the protective layer 13 is formed on the reflective layer 12, this is the difference in reflectance between the surface of the protective layer 13 and the surface of the low reflective layer 15.
In the EUV mask blank 1 of the present invention, the low reflection layer 15 is formed on the absorber layer 14 to reflect the light in the wavelength range of mask pattern inspection light (190 to 260 nm), particularly in the wavelength range of 190 to 200 nm. The rate is very low. Specifically, when the surface of the low reflection layer 15 is irradiated with light in the wavelength range of 190 to 200 nm, the light reflection of the surface of the low reflection layer 15 with respect to the wavelength range (190 to 200 nm) of the mask pattern inspection light. The rate is preferably 15% or less, more preferably 14.5% or less, and even more preferably 14% or less.
If the maximum light reflectance on the surface of the low reflection layer 15 is 15% or less with respect to the wavelength range of the inspection light of the mask pattern of 190 to 200 nm, the wavelength of the inspection light of the mask pattern can be determined in the most promising wavelength range in the future. The contrast at the time of inspection is good. Specifically, with respect to the wavelength range (190 to 200 nm) of the inspection light of the mask pattern, the reflected light on the surface of the reflective layer 12 (the surface of the protective layer 13 when the protective layer 13 is formed on the reflective layer 12) The contrast between the reflected light on the surface of the low reflective layer 15 and the reflected light on the surface of the low reflective layer 15 is 60% or more.

In this specification, the contrast can be obtained using the following equation.
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
Here, R ₂ is the reflectance at the surface of the reflective layer 12 with respect to the wavelength of the inspection light. However, when the protective layer 13 is formed on the reflective layer 12, the reflectance is the surface of the protective layer 13. R ₁ is the reflectance at the surface of the low reflection layer 15 with respect to the wavelength of the inspection light. The above R ₁ and R ₂ are, as shown in FIG. 2, is measured in a state of forming a pattern on the absorber layer 14 and the low reflective layer 15 of the EUV mask blank 1 shown in Figure 1. The R ₂ is a value measured on the surface of the reflective layer 12 or the protective layer 13 exposed to the outside after the absorber layer 14 and the low reflective layer 15 are removed by pattern formation in FIG. 2, and R ₁ is the pattern formation. This is a value measured on the surface of the low reflective layer 15 remaining without being removed by.
In the present invention, the contrast represented by the above formula is more preferably 60.5% or more, and further preferably 61% or more.

In order to achieve the above characteristics, the low reflective layer 15 is preferably made of a material having a refractive index higher than that of the absorber layer 14 with respect to the wavelength range of the inspection light of the mask pattern, and its crystalline state is preferably amorphous.
The low reflective layer 15 of the EUV mask blank 1 of the present invention contains at least one of aluminum (Al) and zirconium (Zr), and at least one of oxygen (O) and nitrogen (N). Achieve properties. Here, the low reflection layer 15 may contain only one or both of Al and Zr. Moreover, only one or both of O and N may be contained.
In addition, when the low reflection layer 15 contains at least one of Al and Zr and at least one of O and N, the adhesiveness with the resist applied at the time of mask pattern formation becomes good.
The low reflection layer 15 preferably contains the above-described elements in a specific ratio described below.

The low reflection layer 15 preferably has a total content of Al and Zr of 20 to 70 at%, preferably a total content of O and N of 30 to 80 at%, and includes Al, Zr, O, and N. The total content is preferably 95 to 100 at%.
If the total content of Al and Zr is less than 20 at%, the conductivity of the low reflection layer 15 is lowered, and there is a possibility that a charge-up problem occurs when drawing an electron beam on the low reflection layer 15. If the total content of Al and Zr is more than 70 at%, there is a possibility that the light reflectivity with respect to the wavelength range of the inspection light of the mask pattern cannot be made sufficiently low. If the total content of O and N is less than 30 at%, there is a possibility that the light reflectivity with respect to the wavelength range of the inspection light of the mask pattern cannot be made sufficiently low. If the total content of O and N is more than 80 at%, the insulating property of the low reflective layer 15 is increased, and there is a possibility that problems such as charge-up occur when an electron beam is drawn on the low reflective layer 15. If the total content of Al, Zr, O and N is less than 95 at%, there is a possibility that the light reflectance for the wavelength range of the inspection light of the mask pattern cannot be made sufficiently low.

  The total content of Al and Zr is more preferably 25 to 70 at%, further preferably 25 to 65 at%, further preferably 30 to 65 at%, and preferably 30 to 40 at%. Particularly preferred. Further, the total content of O and N is more preferably 30 to 75 at%, further preferably 35 to 75 at%, further preferably 35 to 70 at%, and 60 to 70 at%. It is particularly preferred. The total content of Al, Zr, O and N is more preferably 96 to 100 at%, further preferably 97 to 100 at%, and particularly preferably 98 to 100 at%.

  When the low reflective layer 15 contains both Al and Zr, the compositional (atomic) ratio of Al and Zr is Al: Zr = 9: 1 to 1: 9, so that the wavelength range of the inspection light of the mask pattern It is preferable because the light reflectance with respect to can be sufficiently lowered. The composition ratio of Al and Zr is more preferably Al: Zr = 9: 1 to 2: 8, further preferably Al: Zr = 9: 1 to 3: 7, and 5: 1 to 1: 1 is particularly preferred. In addition, it is preferable in terms of optical properties that the Al content is larger than the Zr content.

  When the low reflection layer 15 contains both O and N, the composition ratio (atomic) of O and N is O: N = 9: 1 to 1: 9. This is preferable because the light reflectivity with respect to the wavelength region can be sufficiently lowered and the smoothness of the film can be obtained. The composition ratio of O and N is more preferably O: N = 9: 1 to 2: 8, further preferably O: N = 9: 1 to 3: 7, and 9: 1 to 4: 1 is more preferable. The oxygen content is preferably optically higher than the nitrogen content.

  The low reflective layer 15 preferably has an Al content of 10 to 50 at%, more preferably 15 to 45 at%. Moreover, it is preferable that content of Zr is 2-20 at%, and it is more preferable that it is 5-15 at%. Moreover, it is preferable that content of O is 30-80 at%, and it is more preferable that it is 40-70 at%. Moreover, it is preferable that content of N is 2-25 at%, and it is more preferable that it is 5-15 at%.

Moreover, it is preferable that the low reflection layer 15 does not contain Ta. If the low reflection layer 15 contains Ta, it is not preferable because the light reflectance of the mask pattern with respect to the wavelength range of the inspection light cannot be sufficiently lowered. When the low reflective layer 15 contains Ta, the Ta content in the low reflective layer 15 is preferably 40 at% or less, more preferably 60 at% or less, compared to the Ta content in the absorber layer 14. .
Moreover, it is preferable that the low reflection layer 15 does not contain Cr or Ti.

Specific examples of the low reflective layer 15 containing the above elements include metal compound films such as AlO, AlN, AlON, ZrO, ZrN, ZrON, AlZrO, AlZrN, and AlZrON. Among these, AlO, AlN, AlON, AlZrO, and AlZrON are preferable because the light reflectivity with respect to the wavelength range of the inspection light of the mask pattern can be particularly lowered, AlZrON, AlON, and AlN are more preferable, and AlZrON is further preferable. Is preferred.
The low reflection layer 15 may be a single layer film of any of the above metal compound films, or may be a laminate of two or more metal compound films. Moreover, the gradient composition film | membrane from which a film | membrane composition changes in the thickness direction of a film | membrane may be sufficient.

Since the low reflection layer 15 has the above-described configuration, the crystal state thereof is preferably amorphous. Note that in this specification, the phrase “crystalline state is amorphous” includes a microcrystalline structure other than an amorphous structure having no crystal structure.
When the low reflective layer 15 is an amorphous structure film or a microcrystalline structure film, the surface roughness (rms) of the surface of the low reflection layer 15 is preferably 0.5 nm or less. Here, the surface roughness of the surface of the absorber layer 15 can be measured using an atomic force microscope (Atomic Force Microscope). If the surface roughness of the surface of the low reflection layer 15 is large, the edge roughness of the pattern formed on the low reflection layer 15 increases, and the dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the low reflection layer 15 is required to be smooth.
If the surface roughness (rms) of the surface of the low reflection layer 15 is 0.5 nm or less, the surface of the low reflection layer 15 is sufficiently smooth, and there is no possibility that the dimensional accuracy of the pattern is deteriorated due to the influence of edge roughness. The surface roughness (rms) of the surface of the low reflective layer 15 is more preferably 0.4 nm or less, and further preferably 0.3 nm or less. Moreover, it is preferable that the low reflection layer 15 is an outermost layer.

  It can be confirmed by the X-ray diffraction (XRD) method that the crystal state of the low reflection layer 15 is amorphous, that is, an amorphous structure or a microcrystalline structure. If the crystal state of the low reflective layer 15 is an amorphous structure or a microcrystalline structure, a sharp peak is not observed in a diffraction peak obtained by XRD measurement.

  As described above, the total film thickness of the absorber layer 14 and the low reflective layer 15 is preferably 40 to 200 nm, more preferably 50 to 200 nm, still more preferably 50 to 150 nm, 50 It is particularly preferable that the thickness is ˜100 nm. However, if the film thickness of the low reflection layer 15 is larger than the film thickness of the absorber layer 14, the EUV light absorption characteristics in the absorber layer 14 may be deteriorated. It is preferably smaller than the film thickness of the layer. For this reason, the thickness of the low reflection layer 15 is preferably 3 to 30 nm, preferably 5 to 20 nm, and more preferably 5 to 15 nm.

The low reflection layer 15 having the above-described configuration can be formed by performing a sputtering method using a target including at least one of Al and Zr, for example, a magnetron sputtering method or an ion beam sputtering method.
Here, in the case of using a target containing at least one of Al and Zr, use of two kinds of metal targets, that is, an Al target and a Zr target, and a compound target containing Al and Zr Including any of the above.
Use of two types of metal targets is convenient for adjusting the constituent components of the low reflective layer 15. On the other hand, when using a compound target, it is preferable to adjust the target composition in advance so that the formed low reflection layer 15 has a desired composition.
The low reflective layer 15 having the above-described configuration includes an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), oxygen (O), and It is formed by performing a sputtering method using a target containing at least one of Al and Zr in an atmosphere containing at least one of nitrogen (N).

In order to form the low reflection layer 15 on the absorber layer 14 by the method described above, specifically, the following film formation conditions may be used.
Film formation condition of the low reflection layer 15: In the case of an AlO film Target: Al target Sputtering gas: Mixed gas of Ar and O ₂ (Ar gas concentration: 3 to 80 vol%, preferably 5 to 70 vol%, more preferably 10-60 vol%, O ₂ gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably 1 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation condition of the low reflection layer 15: In the case of an AlN film Target: Al target Sputtering gas: Mixed gas of Ar and N ₂ (Ar gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%, N ₂ gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably 1 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Deposition conditions for the low reflective layer 15: For the AlON film <br/> target: Al target Sputtering gas: Ar, O ₂ and a mixed gas of N ₂ (Ar gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10~60vol%, O ₂ gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10~60vol%, N ₂ gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10～60Vol% is; gas pressure preferably 1 × 10 ^-2 Pa~40 × 10-1Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation condition of the low reflective layer 15: ZrO film Target: Zr target Sputter gas: Ar and O ₂ mixed gas (Ar gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%, O ₂ gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably 1 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation condition of the low reflection layer 15: ZrN film Target: Zr target Sputter gas: Ar and N ₂ mixed gas (Ar gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%, N ₂ gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably 1 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation conditions for the low reflective layer 15: ZrON film Target: Zr target Sputter gas: Ar, O ₂ and N ₂ mixed gas (Ar gas concentration: 3 to 80 vol%, preferably 5 to 70 vol%, more preferably 10~60vol%, O ₂ gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10~60vol%, N ₂ gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10～60Vol% is; gas pressure preferably 1 × 10 ^-2 Pa~40 × 10-1Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation conditions of the low reflection layer 15: In the case of an AlZrO film Target: Al target and Zr target Sputtering gas: Ar and O ₂ mixed gas (Ar gas concentration: 3 to 80 vol%, preferably 5 to 70 vol%, More preferably 10 to 60 vol%, O ₂ gas concentration 3 to 80 vol%, preferably 5 to 70 vol%, more preferably 10 to 60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation conditions for the low reflection layer 15: In the case of an AlZrN film Target: Al target and Zr target Sputtering gas: Ar and N ₂ mixed gas (Ar gas concentration: 3 to 80 vol%, preferably 5 to 70 vol%, More preferably 10 to 60 vol%, N ₂ gas concentration 3 to 80 vol%, preferably 5 to 70 vol%, more preferably 10 to 60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 ⁻¹ Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation conditions for the low reflective layer 15: In the case of an AlZrON film Target: Al target and Zr target Sputter gas: Mixed gas of Ar, O ₂ and N ₂ (Ar gas concentration: 3 to 80 vol%, preferably 5 to 5%) 70 vol%, more preferably 10~60vol%, O ₂ gas concentration 3~80vol%, preferably 5~70vol%, more preferably 10~60vol%, N ₂ gas concentration 3~80vol%, preferably 5～70Vol% , more preferably 10~60vol%; gas pressure preferably 1 × 10 ^-2 Pa~40 × 10-1Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

Film formation condition of the low reflection layer 15: In the case of an AlZrON film Target: AlZr compound target (example: Al: Zr = 50: 50)
Sputtering gas: Mixed gas of Ar, O ₂ and N ₂ (Ar gas concentration 3 to 80 vol%, preferably 5 to 70 vol%, more preferably 10 to 60 vol%, O ₂ gas concentration 3 to 80 vol%, preferably 5 to 5 vol. 70 vol%, more preferably 10-60 vol%, N ₂ gas concentration 3-80 vol%, preferably 5-70 vol%, more preferably 10-60 vol%; gas pressure, preferably 1 × 10 ⁻² Pa to 40 × 10 − 1 Pa, more preferably ^{1 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.1 to 60 nm / min, preferably 0.5 to 45 nm / min, more preferably 1 to 30 nm / min
When an inert gas other than Ar is used, the concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

The EUV mask blank 1 of the present invention may have a functional film known in the field of EUV mask blanks in addition to the reflective layer 12, the protective layer 13, the absorber layer 14, and the low reflective layer 15. As a specific example of such a functional film, for example, as described in JP-A-2003-501823, a high dielectric applied to the back side of the substrate in order to promote electrostatic chucking of the substrate. A functional coating. Here, the back surface of the substrate refers to the surface of the substrate 11 in FIG. 1 opposite to the side on which the reflective layer 12 is formed. For the high dielectric coating applied to the back surface of the substrate for such a purpose, the electrical conductivity and thickness of the constituent material are selected so that the sheet resistance is 100Ω / □ or less. The constituent material of the high dielectric coating can be widely selected from those described in known literature. For example, a high dielectric constant coating described in JP-A-2003-501823, specifically, a coating made of silicon, TiN, molybdenum, chromium, or TaSi can be applied. The thickness of the high dielectric coating can be, for example, 10 to 1000 nm.
The high dielectric coating can be formed using a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or an electrolytic plating method.

  An EUV mask can be manufactured by patterning at least the absorption layer of the mask blank of the present invention. The patterning method of the absorber layer is not particularly limited, and for example, a method of applying a resist on the absorber layer to form a resist pattern and etching the absorber layer using this as a mask can be employed. The resist material and the resist pattern drawing method may be appropriately selected in consideration of the material of the absorber layer and the like. The method for etching the absorber layer is not particularly limited, and dry etching such as reactive ion etching or wet etching can be employed. After patterning the absorber layer, the EUV mask is obtained by stripping the resist with a stripping solution.

  A method for manufacturing a semiconductor integrated circuit using the EUV mask according to the present invention will be described. The present invention can be applied to a method for manufacturing a semiconductor integrated circuit by a photolithography method using EUV light as an exposure light source. Specifically, a substrate such as a silicon wafer coated with a resist is placed on a stage, and the EUV mask is installed in a reflective exposure apparatus configured by combining a reflecting mirror. Then, the EUV light is irradiated from the light source to the EUV mask through the reflecting mirror, and the EUV light is reflected by the EUV mask and irradiated to the substrate coated with the resist. By this pattern transfer process, the circuit pattern is transferred onto the substrate. The substrate on which the circuit pattern has been transferred is subjected to development to etch the photosensitive portion or the non-photosensitive portion, and then the resist is removed. A semiconductor integrated circuit is manufactured by repeating such steps.

The present invention will be further described below using examples.
Example 1
In this example, the EUV mask blank 1 shown in FIG. 1 was produced.
As the substrate 11 for film formation, a SiO ₂ —TiO ₂ glass substrate (outer dimension of about 6 inches (about 152 mm) square, thickness of about 6.3 mm) was used. This glass substrate has a thermal expansion coefficient of 0.2 × 10 ⁻⁷ / ° C., a Young's modulus of 67 GPa, a Poisson's ratio of 0.17, and a specific rigidity of 3.07 × 10 ⁷ m ² / s ² . This glass substrate was polished to form a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less.

A high dielectric coating having a sheet resistance of 100Ω / □ was applied to the back side of the substrate 11 by depositing a Cr film having a thickness of 100 nm using a magnetron sputtering method.
A substrate 11 (outer diameter 6 inches (152 mm) square, thickness 6.3 mm) is fixed to a flat electrostatic chuck having a flat plate shape by using the formed Cr film, and ion beam sputtering is performed on the surface of the substrate 11. The Si / Mo multilayer reflective film (reflective layer 12) having a total film thickness of 272 nm ((4.5 nm + 2.3 nm) × 40) is obtained by repeating 40 cycles of alternately forming the Si film and the Mo film using the method. Formed.
Further, a protective layer 13 was formed by forming a Ru film (film thickness: 2.5 nm) on the Si / Mo multilayer reflective film (reflective layer 12) using an ion beam sputtering method.

The deposition conditions for the Si film, the Mo film, and the Ru film are as follows.
Conditions for forming the Si film Target: Si target (boron doped)
Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.077 nm / sec
Film thickness: 4.5nm
Conditions for forming the Mo film Target: Mo target Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.064 nm / sec
Film thickness: 2.3 nm
Ru film formation conditions Target: Ru Target sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 500V
Deposition rate: 0.023 nm / sec
Film thickness: 2.5nm

Next, a TaNH film containing Ta, N, and H was formed as the absorber layer 14 on the protective layer 13 by using a magnetron sputtering method.
The absorber layer 14 (TaNH film) was formed by the following method. The film composition includes an X-ray Photoelectron Spectrometer (manufactured by PERKIN ELEMER-PHI), a secondary ion mass spectrometer (Secondary Ion Mass Spectrometer) (manufactured by PHI-ATOMIKA), and Rutherford backscattering spectrometer (manufactured by Rutherford). Measurement is performed using Ruferford Back Scattering Spectroscopy (manufactured by Kobe Steel). The composition ratio (at%) of the absorber layer 14 (TaNH film) is Ta: N: H = 58.1: 38.5: 3.4 (Ta content is 58.1 at%, N content is 38.5 at%, H content 3.4 at%). The O content in the absorber layer is 0.05 at% or less.
Deposition conditions <br/> target of the absorber layer 14 (TaNH film): Ta target Sputtering gas: mixed gas of Ar and N ₂ and _{H 2 (Ar: 89vol%,} N 2: 8.3vol%, H 2: (2.7 vol%, gas pressure: 0.46 Pa)
Input power: 300W
Deposition rate: 1.5 nm / min
Film thickness: 60nm

Next, a low reflection layer 15 (AlZrON film) containing Al, Zr, O and N is formed on the absorber layer 14 by using a magnetron sputtering method, whereby the reflection layer 12 and the protection layer are formed on the substrate 11. The EUV mask blank 1 in which the layer 13, the absorber layer 14, and the low reflection layer 15 were formed in this order was obtained.
The film forming conditions of the low reflective layer 15 (AlZrON film) are as follows.
Film formation conditions for the low reflective layer 15 (AlZrON film) Target: Al target and Zr target Sputter gas: Mixed gas of Ar, O ₂ and N ₂ (Ar: 46 vol%, O ₂ : 8 vol%, N ₂ : 46 vol%, gas pressure: 0.3 Pa)
Input power: Al target 150W, Zr target 75W
Deposition rate: 2.5 nm / min
Film thickness: 10nm

The following evaluations (1) to (5) were performed on the low reflective layer 15 (AlZrON film) of the EUV mask blank obtained by the above procedure.
(1) Film composition The composition of the low-reflection layer 15 (AlZrON film) is determined using an X-ray photoelectron spectrometer (manufactured by PERKIN ELEMER-PHI), a secondary ion mass spectrometer (Secondary Ion Mass Spectrometer). (PHI-ATOMIKA), Rutherford Back Scattering Spectroscopy (Kobe Steel) The composition ratio (at%) of the low reflection layer is Al: Zr: O: N = 21: 11: 60: 8.

(2) Crystal State The crystal state of the absorber layer 15 (AlZrON film) was confirmed with an X-ray diffractometer (X-Ray Diffractometer) (manufactured by RIGAKU). Since no sharp peak was observed in the obtained diffraction peak, it was confirmed that the crystalline state of the low reflective layer 15 (AlZrON film) was an amorphous structure or a microcrystalline structure.

(3) Surface roughness The surface roughness of the low-reflection layer 15 (AlZrON film) is measured by a dynamic force mode using an atomic force microscope (SII, SPI-3800). The surface roughness measurement area is 1 μm × 1 μm, and SI-DF40 (manufactured by SII) is used as the cantilever.
The surface roughness (rms) of the low reflection layer was 0.12 nm.

(4) Evaluation of reflection characteristics for pattern inspection wavelength (contrast evaluation)
In this example, when the protective layer 13 (Ru film) is formed, the reflectance of the mask pattern inspection light (wavelength 257 nm, 199 nm, 193 nm) on the surface of the protective layer 13 is measured by a spectrophotometer (HITACH UV-4100). It measured using. Moreover, after forming the low reflection layer 15 (SiN film), the reflectance of the inspection light of the mask pattern on the surface of the low reflection layer was measured. As a result, the reflectances for the wavelengths of 199 nm and 193 nm on the surface of the protective layer 13 were 53.6% and 55%, respectively. On the other hand, the reflectance with respect to each wavelength on the surface of the low reflective layer 15 (AlZrON film) was 3.2% and 2.5%, both of which were 15% or less. When the contrast was obtained using these results and the above formula, the contrast at each wavelength was as follows.
Contrast at a wavelength of 199 nm: 88.7%
Contrast at a wavelength of 193 nm: 91.3%
The contrast between the surface of the protective layer 13 and the surface of the low reflection layer 15 was 60% or more with respect to all the wavelength ranges of the inspection light of the mask pattern, and a sufficient contrast was obtained. About the obtained EUV mask blank 1, the EUV light (wavelength 13.5nm) is irradiated to the surface of the low reflection layer 15 (AlZrON film | membrane), and the reflectance of EUV light is measured. As a result, the reflectance of EUV light is 0.8%.

(5) Evaluation of resist adhesion In this example, the resist adhesion is evaluated by the following method at the stage where the low reflection layer 15 (AlZrON film) is formed. On the low reflection layer 15, a chemical amplification type positive resist for electron beam exposure (FEP171) is applied by spin coating to a thickness of 200 nm, and then dried by heating at 120 ° C. for 2 minutes on a hot plate. Then, it exposes using an electron beam drawing apparatus (made by Elionix), Furthermore, the development process and rinse process by a developing solution (TMAH: tetramethylhydroxide) are implemented, and a 100 nm line and space is formed. When the formed resist pattern is confirmed, it is confirmed that there is no disappearance of the resist pattern and there is sufficient adhesion.

Example 2
Example 2 was performed in the same procedure as Example 1 except that the low reflection layer 15 was an AlON film containing Al, O, and N.
The film formation conditions of the low reflection layer 15 (AlON film) are as follows.
Film formation conditions for the low reflective layer 15 (AlON film) Target: Al target Sputter gas: Mixed gas of Ar, O ₂ and N ₂ (Ar: 50 vol%, O ₂ : 12.5 vol%, N ₂ : (37.5 vol%, gas pressure: 0.3 Pa)
Input power: Al target 150W
Deposition rate: 0.56 nm / min
Film thickness: 10nm
The film composition of the low reflective layer 15 (AlON film) is examined in the same manner as in Example 1. The composition ratio (at%) of the low reflective layer 15 is Al: O: N = 32: 56: 12.
The crystal state of the low reflective layer 15 (AlON film) was examined in the same manner as in Example 1. It was confirmed that the crystalline state of the low reflective layer 15 was an amorphous structure or a microcrystalline structure.
The surface roughness of the low reflective layer 15 (AlON film) was examined in the same manner as in Example 1. The surface roughness (rms) of the low reflective layer 15 was 0.45 nm.
The obtained EUV mask blank 1 was subjected to reflection characteristic evaluation (contrast evaluation) in the same procedure as in Example 1. Specifically, the reflectivity with respect to wavelengths of 199 nm and 193 nm on the surface of the low reflective layer 15 (AlON film) was 11.3% and 10.5%, both of which were 15% or less. From these results and the reflectance of the surface of the protective layer 13, the contrast was determined using the above-described formula, and the contrast at each wavelength was as follows.
Contrast at a wavelength of 199 nm: 65.1%
Contrast at a wavelength of 193 nm: 67.9%
The contrast between the surface of the protective layer 13 and the surface of the low reflection layer 15 was 60% or more with respect to all the wavelength ranges of the inspection light of the mask pattern, and a sufficient contrast was obtained. About the obtained EUV mask blank 1, the EUV light (wavelength 13.5nm) is irradiated to the surface of the low reflection layer 15 (AlON film | membrane), and the reflectance of EUV light is measured. As a result, the reflectance of EUV light is 0.7%.
At the stage where the low reflective layer 15 (AlON film) is formed, the adhesion to the resist is examined in the same manner as in Example 1. When the resist pattern formed on the low reflective layer 15 (AlON film) is confirmed, it is confirmed that there is no disappearance of the resist pattern and sufficient adhesion is obtained.

Example 3
Example 3 was performed in the same procedure as Example 1 except that the low reflective layer 15 was a ZrON film containing Zr, O, and N.
The film formation conditions of the low reflection layer 15 (ZrON film) are as follows.
Deposition conditions <br/> target of the low reflective layer 15 (ZrON film): Zr target Sputtering gas: Ar, O ₂ and a mixed gas of _{N 2 (Ar: 50vol%,} O 2: 37.5vol%, N 2: (12.5 vol%, gas pressure: 0.3 Pa)
Input power: Zr target 150W
Deposition rate: 1.13 nm / min
Film thickness: 10nm
The film composition of the low reflective layer 15 (ZrON film) is examined in the same manner as in Example 1. The composition ratio (at%) of the low reflective layer 15 is Zr: O: N = 34: 58: 8.
The crystal state of the low reflection layer 15 (ZrON film) was examined in the same manner as in Example 1. It was confirmed that the crystalline state of the low reflective layer 15 was an amorphous structure or a microcrystalline structure.
The surface roughness of the low reflective layer 15 (ZrON film) was examined in the same manner as in Example 1. The surface roughness (rms) of the low reflective layer 15 was 0.45 nm.
The obtained EUV mask blank 1 was subjected to reflection characteristic evaluation (contrast evaluation) in the same procedure as in Example 1. Specifically, the reflectivity for wavelengths of 199 nm and 193 nm on the surface of the low reflective layer 15 (ZrON film) was 12.8% and 13.2%, both of which were 15% or less. From these results and the reflectance of the surface of the protective layer 13, the contrast was determined using the above-described formula, and the contrast at each wavelength was as follows.
Contrast at a wavelength of 199 nm: 61.4%
Contrast at a wavelength of 193 nm: 61.3%
The contrast between the surface of the protective layer 13 and the surface of the low reflection layer 15 was 60% or more with respect to all the wavelength ranges of the inspection light of the mask pattern, and a sufficient contrast was obtained. About the obtained EUV mask blank 1, the EUV light (wavelength 13.5nm) is irradiated to the surface of the low reflection layer 15 (ZrON film | membrane), and the reflectance of EUV light is measured. As a result, the reflectance of EUV light is 0.8%.
At the stage where the low reflective layer 15 (ZrON film) is formed, the adhesion with the resist is examined in the same manner as in Example 1. When the resist pattern formed on the low reflective layer 15 (ZrON film) is confirmed, it is confirmed that there is no disappearance of the resist pattern and there is sufficient adhesion.

Comparative Example 1
Comparative Example 1 was performed in the same procedure as Example 1 except that the low reflective layer 15 was a SiN film containing Si and N.
The film formation conditions of the low reflection layer 15 (SiN film) are as follows.
Low reflective layer 15 deposition conditions <br/> target (SiN film): Si target Sputtering gas: Ar and N ₂ mixed gas _{(Ar: 20vol%, N 2} : 80vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 2 nm / min
Film thickness: 10nm
The film composition of the low reflective layer 15 (SiN film) is examined in the same manner as in Example 1. The composition ratio (at%) of the low reflective layer 15 is Si: N = 34: 66.
The crystal state of the low reflective layer 15 (SiN film) was examined in the same manner as in Example 1. It was confirmed that the crystalline state of the low reflective layer 15 was an amorphous structure or a microcrystalline structure.
The surface roughness of the low reflective layer 15 (SiN film) was examined in the same manner as in Example 1. The surface roughness (rms) of the low reflective layer 15 was 0.45 nm.
The obtained EUV mask blank 1 was subjected to reflection characteristic evaluation (contrast evaluation) in the same procedure as in Example 1. Specifically, the reflectivity with respect to wavelengths of 199 nm and 193 nm on the surface of the low reflective layer 15 (SiN film) was 2.4% and 2.7%, both of which were 15% or less. From these results and the reflectance of the surface of the protective layer 13, the contrast was determined using the above-described formula, and the contrast at each wavelength was as follows.
Contrast at a wavelength of 199 nm: 91.3%
Contrast at a wavelength of 193 nm: 90.4%
The contrast between the surface of the protective layer 13 and the surface of the low reflection layer 15 was 60% or more with respect to all the wavelength ranges of the inspection light of the mask pattern, and a sufficient contrast was obtained. About the obtained EUV mask blank 1, the EUV light (wavelength 13.5nm) is irradiated to the surface of the low reflection layer 15 (SiN film), and the reflectance of EUV light is measured. As a result, the reflectance of EUV light is 0.8%.
At the stage where the low reflective layer 15 (SiN film) is formed, the adhesion to the resist is examined in the same manner as in Example 1. The resist pattern formed on the low reflective layer 15 (SiN film) disappears in the development process and the rinsing process, and it is confirmed that the adhesion is insufficient.

1: EUV mask blank 11: Substrate 12: Reflective layer (multilayer reflective film)
13: Protective layer 14: Absorber layer 15: Low reflective layer

Claims (14)

For EUV lithography, a reflective layer that reflects EUV light, an absorber layer that absorbs EUV light, and a low reflective layer for mask pattern inspection light (wavelength 190 nm to 260 nm) are formed in this order on a substrate. A reflective mask blank,
The low reflection layer contains at least one of aluminum (Al) and zirconium (Zr), and at least one of oxygen (O) and nitrogen (N) ;
The total content of Al and Zr is 20 to 70 at%, the total content of O and N is 30 to 80 at%, and the total content of Al, Zr, O and N is 95 to 100 at% A reflective mask blank for EUV lithography, characterized in that it exists . The reflective mask blank for EUV lithography according to claim 1, wherein the surface roughness (rms) of the surface of the low reflective layer is 0.5 nm or less . The reflective mask blank for EUV lithography according to claim 1 or 2, wherein the crystal structure of the surface of the low reflective layer is amorphous . The reflective mask blank for EUV lithography according to any one of claims 1 to 3, wherein the low reflective layer has a thickness of 3 to 30 nm . The reflective mask blank for EUV lithography according to any one of claims 1 to 4, wherein the absorber layer contains tantalum (Ta) as a main component . The absorber layer is mainly composed of tantalum (Ta) and is composed of hafnium (Hf), silicon (Si), zirconium (Zr), germanium (Ge), boron (B), nitrogen (N), and hydrogen (H). The reflective mask blank for EUV lithography according to any one of claims 1 to 5, comprising at least one element selected . The reflective mask blank for EUV lithography according to any one of claims 1 to 6, wherein the absorber layer has an oxygen (O) content of less than 25 at% . The reflective mask blank for EUV lithography according to any one of claims 1 to 7, wherein a total film thickness of the absorber layer and the low reflection layer is 40 to 200 nm . A protective layer is formed between the reflective layer and the absorber layer to protect the reflective layer when forming a pattern on the absorber layer.
9. The reflective mask blank for EUV lithography according to claim 1, wherein the contrast represented by the following formula is 60% or more .
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
( Where R ₂ is the reflectance on the surface of the protective layer with respect to the wavelength of the inspection light of the mask pattern (190 nm to 260 nm), and R ₁ is the surface of the low reflection layer with respect to the wavelength of the inspection light of the mask pattern (190 nm to 260 nm)) The reflectance at. The reflective mask blank for EUV lithography according to claim 9, wherein the protective layer is formed of any one of Ru, Ru compound, SiO ₂ and CrN . The reflective type for EUV lithography according to any one of claims 1 to 10, wherein the reflectance of the surface of the low reflective layer with respect to the wavelength (190 nm to 260 nm) of the inspection light of the mask pattern is 15% or less. Mask blank . The low reflective layer includes an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), oxygen (O), and nitrogen (N). It forms by performing the sputtering method using the target containing at least one of Al and Zr in the atmosphere containing at least one of these. Reflective mask blank for EUV lithography . The reflective mask for EUV lithography which patterned the absorber layer and low reflective layer of the reflective mask blank for EUV lithography in any one of Claims 1-12 . A method for manufacturing a semiconductor integrated circuit, wherein a semiconductor integrated circuit is manufactured by exposing an object to be exposed using the reflective mask for EUV lithography according to claim 13 .

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