JP6186962B2 - Reflective mask blank for EUV lithography and reflective mask for EUV lithography - Google Patents

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, and the EUV mask blank. The present invention relates to a reflective mask for EUV lithography (hereinafter referred to as “EUV mask” in this specification) formed by forming a mask pattern on an absorption layer.

  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 light in the EUV wavelength region shorter than the ArF laser (hereinafter referred to as “EUV light”), 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 cannot be used. For this reason, in the EUV light lithography, a reflective optical system, that is, an EUV mask and a mirror are used.

The mask blank is a laminated body before patterning used for photomask manufacturing. The EUV mask blank has a structure in which a reflective layer that reflects EUV light and an absorption layer that absorbs EUV light are formed in this order on a glass substrate or the like.
As a reflective layer, a low refractive index layer having a low refractive index with respect to EUV light and a high refractive index layer having a high refractive index with respect to EUV light are alternately laminated, so that EUV light is applied to the surface of the layer. A multilayer reflective film having an increased light reflectance upon irradiation is usually used. As the low refractive index layer of the multilayer reflective film, a molybdenum (Mo) layer is usually used, and as the high refractive index layer, a silicon (Si) layer is usually used.
For the absorption layer, a material having a high absorption coefficient for EUV light, specifically, a material mainly composed of, for example, chromium (Cr) or tantalum (Ta) is used.

  The multilayer reflective film and the absorption layer are formed on the optical surface of the glass substrate using an ion beam sputtering method or a magnetron sputtering method. When forming the multilayer reflective film and the absorbing layer, the glass substrate is held by the support means. There are mechanical chucks and electrostatic chucks as means for supporting the glass substrate, but electrostatic chucks are preferably used from the viewpoint of dust generation. An electrostatic chuck is also used as a supporting means for the glass substrate during the mask patterning process or during mask handling during exposure.

The electrostatic chuck is a technique conventionally used as a means for supporting a silicon wafer in a semiconductor device manufacturing process. For this reason, in the case of a substrate having a low dielectric constant and conductivity, such as a glass substrate, it is necessary to apply a high voltage in order to obtain a chucking force equivalent to that in the case of a silicon wafer. There is sex.
In order to solve such a problem, Patent Document 1 discloses a multilayer reflection in which a conductive film (back conductive film) is formed on the opposite side of the multilayer reflective film across the substrate in order to promote electrostatic chucking of the substrate. A film substrate, a reflective mask blank for exposure, and a mask for exposure are described. This conductive film is a metal nitride film, and examples of the metal include chromium, tantalum, molybdenum, and silicon.

Japanese Patent Laid-Open No. 2005-210093

In the EUV mask and the EUV mask blank used therefor, there may be a problem of deformation of the substrate caused by internal reflection in the multilayer reflective film as the reflective layer or the absorbing layer. Conventionally, there has been a tendency to increase the film thickness of the back conductive film in order to offset this internal stress.
In addition, a glass substrate is locally irradiated by irradiating a pulse laser having a wavelength of 532 nm (any wavelength may be used in the wavelength range of 400 to 800 nm) from the back side of the EUV mask or EUV mask blank. A technique for improving the deformation of the substrate due to internal stress in the multilayer reflective film or the absorbing layer by heating to a new level is being introduced.
By applying this technique, the film thickness of the back surface conductive film can be set to a minimum film thickness necessary to achieve the requirements regarding the sheet resistance value. As a result, the time required for forming the back surface conductive film is shortened, and the yield in manufacturing the EUV mask blank is improved.
However, when this technique is applied, the back surface conductive film has a high light transmittance at a wavelength of 532 nm (an arbitrary wavelength may be used in the wavelength range of 400 to 800 nm), specifically, in this wavelength region. The light transmittance is required to be 10% or more. In general, to increase the light transmittance, the film thickness may be reduced. However, if the film thickness of the back surface conductive film is reduced, the sheet resistance value may increase, and there is a possibility that the requirement cannot be achieved.

  The present invention aims to provide an EUV mask blank on which a back conductive film is formed having a high light transmittance at a wavelength of 400 to 800 nm and a low sheet resistance, in order to solve the above-described problems of the prior art. To do.

In order to achieve the above-described object, the present invention includes a reflective layer that reflects EUV light on one surface of a substrate and an absorbing layer that absorbs EUV light in this order, and a conductive layer on the other surface of the substrate. A reflective mask blank for EUV lithography in which a film is formed,
The conductive film contains at least one selected from the group consisting of chromium (Cr) and tantalum (Ta), and nitrogen (N);
N content in the conductive film is 1 at% or more and 42 at% or less,
Provided is a reflective mask blank for EUV lithography, wherein the following formula is satisfied when the N content in the conductive film is C (at%) and the film thickness of the conductive film is t (nm).
0.15C + 1.68 ≦ t ≦ 0.31C + 11.13

  In the EUV mask blank of the present invention, the conductive film contains Cr and N, the Cr content in the conductive film is 58 at% or more and 99 at% or less, and the N content is 1 at% or more and 42 at%. The following is preferable.

  In the EUV mask blank of the present invention, the conductive film preferably has a thickness of 2 nm to 24 nm.

  In the EUV mask blank of the present invention, the conductive film surface preferably has a surface roughness (rms) of 0.5 nm or less.

  In the EUV mask blank of the present invention, the total content of aluminum (Al) and indium (In) in the conductive film is preferably 5 at% or less.

  In the EUV mask blank of the present invention, the sheet resistance value of the conductive film is preferably 250 Ω / □ or less.

  In the EUV mask blank of the present invention, it is preferable that the conductive film has a light transmittance of 10% or more at a wavelength of 400 to 800 nm.

In the EUV mask blank of the present invention, a protective layer for protecting the reflective layer may be formed between the reflective layer and the absorbent layer when forming a pattern on the absorbent layer.
The protective layer preferably includes Ru or a Ru compound as a constituent material.

  The present invention also provides a reflective mask for EUV lithography obtained by patterning the above EUV mask blank of the present invention.

  Since the EUV mask blank and EUV mask of the present invention have a light transmittance of 10% or more at a wavelength of 400 to 800 nm of the back surface conductive film, a pulse laser in this wavelength region is locally applied from the back side of the EUV mask blank or EUV mask. By locally irradiating and locally heating the glass substrate, it is possible to improve the deformation of the substrate due to internal stress in the multilayer reflective film or the absorption layer. On the other hand, since the sheet resistance value of the back surface conductive film is as low as 250Ω / □ or less, the chucking force by the electrostatic chuck is high.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. FIG. 2 is a graph showing the relationship between the N content in the conductive film and the film thickness of the back conductive film for Examples 1 to 15. FIG. 3 is a graph showing the light transmittance at a wavelength of 400 to 800 nm for Example 1.

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 shown in FIG. 1, a reflective layer 2 that reflects EUV light and an absorption layer 3 that absorbs EUV light are formed in this order on one surface of the substrate 1 (the upper surface of the substrate 1 in the figure). Yes. A conductive film (back conductive film) 4 is formed on the other surface of the substrate 1 (the lower surface of the substrate 1 in the figure).
Hereinafter, individual components of the mask blank of the present invention will be described.

The substrate 1 is required to satisfy characteristics as a substrate for an EUV mask blank.
Therefore, the substrate 1 has a low thermal expansion coefficient (specifically, the thermal expansion coefficient at 20 ° C. is preferably 0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably 0 ± 0.3 × 10 ⁻⁷ / ° C. More preferably 0 ± 0.2 × 10 ⁻⁷ / ° C., further preferably 0 ± 0.1 × 10 ⁻⁷ / ° C., particularly preferably 0 ± 0.05 × 10 ⁻⁷ / ° C.) Those having excellent smoothness, flatness, and resistance to a cleaning liquid used for cleaning a mask blank or a photomask after pattern formation are preferred. Specifically, the substrate 1 is made of glass having a low thermal expansion coefficient, such as SiO ₂ —TiO ₂ glass, but is not limited to this. Crystallized glass, quartz glass, silicon, A substrate such as metal can also be used. Further, a film such as a stress correction film may be formed on the substrate 1.

The substrate 1 has a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less in the standard of JIS-B0601, and high EUV light reflection in a photomask after pattern formation. Rate and transfer accuracy are preferable.
The size and thickness of the substrate 1 are appropriately determined according to the design value of the mask. In the examples described later, SiO ₂ —TiO ₂ glass having an outer shape of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm) was used.
It is preferable that no defects exist on the surface of the substrate 1 on the side where the reflective layer 2 is formed. 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 characteristic particularly required for the reflective layer 2 as a reflective layer of the EUV mask blank is that the reflectance of EUV light is high. Specifically, when the surface of the reflective layer 2 is irradiated with EUV light at an incident angle of 6 degrees, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, more preferably 63% or more, 65% or more is more preferable.

  Since the reflective layer 2 can achieve a high EUV light reflectance, normally, a high refractive layer that exhibits a high refractive index for EUV light and a low refractive index layer that exhibits a low refractive index for EUV light are alternately alternated. A multilayer reflective film laminated a plurality of times is used as the reflective layer 2. In the multilayer reflective film constituting the reflective layer 2, Si is widely used for the high refractive index layer, and Mo 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 / Mo multilayer reflective films and Si / Ru / Mo / Ru multilayer reflective films can also be used.

  The thickness of each layer constituting the multilayer reflective film constituting the reflective layer 2 and the number of repeating units of the layers can be appropriately selected according to the film material used and the reflectance of EUV light required for the reflective layer. Taking the Mo / Si reflective film as an example, in order to make the reflective layer 2 having a maximum reflectance of EUV light of 60% or more, the multilayer reflective film has a film thickness of 2.3 ± 0.1 nm, A Si film 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 2 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 forming a Mo / Si multilayer reflective film by using 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 0.30 nm / sec. using a target, using an Ar gas as a sputtering 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 30 nm / sec. With this as one period, the Mo / Si multilayer reflective film is formed by laminating 30 to 60 periods of the Si film and the Mo film.

The characteristic particularly required for the absorption layer 3 is that the EUV light reflectance is extremely low. Specifically, the maximum light reflectance around a wavelength of 13.5 nm when the surface of the absorbing layer 3 is irradiated with light in the wavelength region of EUV light is preferably 0.5% or less, more preferably 0.1% or less. preferable.
In order to achieve the above characteristics, the absorption layer 3 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, the term “material mainly composed of tantalum (Ta)” means a material containing 40 at% or more of Ta in the material. The absorption layer 3 preferably contains 50 at% or more of Ta, more preferably 55 at% or more.

  In addition to Ta, the material mainly composed of Ta used for the absorption layer 3 is hafnium (Hf), silicon (Si), zirconium (Zr), germanium (Ge), boron (B), palladium (Pd), hydrogen (H ) And nitrogen (N). Specific examples of the material containing the above elements other than Ta include, for example, TaN, TaNH, TaHf, TaHfN, TaBSi, TaBSiN, TaB, TaBN, TaSi, TaSiN, TaGe, TaGeN, TaZr, TaZrN, TaPd, TaPdN, etc. Is mentioned.

Moreover, the thickness of the absorption layer 3 is preferably in the range of 50 to 100 nm.
The absorption layer 3 having the above-described configuration can be formed using a film forming method such as a sputtering method such as a magnetron sputtering method or an ion beam sputtering method.
For example, when a TaNH film is formed as the absorption layer 3 using a magnetron sputtering method, a Ta target is used as a target, and a mixed gas of Ar, N _2, and H ₂ (H ₂ gas concentration 1 to 30 vol%) is used as a sputtering gas. N ₂ gas concentration 5 to 75 vol%, Ar gas concentration 10 to 94 vol%, gas pressure 0.5 × 10 ⁻¹ Pa to 1.0 Pa), input power 300 to 2000 W, film formation rate 0.5 to 60 nm / min Therefore, it is preferable to form a film so as to have a thickness of 20 to 90 nm.

A characteristic required for the conductive film 4 is a low sheet resistance value. The conductive film 4 of the present invention has a sheet resistance value of 250Ω / □ or less. The sheet resistance value is preferably 200Ω / □ or less, more preferably 150Ω / □ or less, further preferably 100Ω / □ or less, and particularly preferably 80Ω / □ or less.
In addition, as a characteristic required for the conductive film 4, a high adhesive force with the substrate 1 can be mentioned. If the adhesion to the substrate 1 is low, the substrate 1 is held by the electrostatic chuck, and when the multilayer reflective film or the absorption layer is formed, film peeling occurs between the substrate 1 and the conductive film 4. Particles may be generated.
Such particles are problematic because they can cause defects in the manufactured EUV mask blank. In terms of preventing film peeling during electrostatic chucking, the conductive film is also required to have excellent surface smoothness and high surface hardness.
Furthermore, the characteristic requested | required of the electrically conductive film 4 of this invention is that the light transmittance of wavelength 400-800 nm is high. This is because, by locally irradiating the pulse laser in this wavelength region and locally heating the glass substrate, deformation of the substrate due to internal stress in the multilayer reflective film or the absorption layer can be improved. The conductive film 4 of the present invention has a light transmittance of 10% or more at a wavelength of 400 to 800 nm. The light transmittance at a wavelength of 400 to 800 nm is preferably 13% or more, more preferably 15% or more, and further preferably 20% or more. In the conductive film 4 of the present invention, as shown in FIG. 3, the light transmittance at a wavelength of 400 to 800 nm often shows a substantially constant value.

In order to achieve the above required characteristics, the conductive film 4 of the present invention contains at least one selected from the group consisting of chromium (Cr) and tantalum (Ta), and nitrogen (N). Specific examples of the conductive film 4 include a CrN film, a TaN film, and a CrTaN film.
Among these, a CrN film is preferable in that it has high resistance to chemicals such as alkali and acid used at the time of general mask blank cleaning and mask cleaning.

The conductive film 4 of the present invention has a nitrogen (N) content of 1 at% or more and 42 at% or less in the conductive film. When the N content in the conductive film 4 is less than 1 at%, the adhesion of the conductive film to the substrate 1 decreases, the surface smoothness of the conductive film 4 decreases, and the surface hardness of the conductive film 4 decreases. There is a point. These problems cause film peeling during electrostatic chucking as described above. On the other hand, if the N content in the conductive film 4 exceeds 42 at%, the sheet resistance value of the conductive film 4 increases.
The N content in the conductive film 4 is preferably 1 at% or more and 40 at% or less, more preferably 1 at% or more and 38 at% or less, further preferably 5 at% or more and 38 at% or less, and particularly preferably 5 at% or more and 35 at% or less.

In the conductive film 4 of the present invention, the balance obtained by subtracting the N content is usually the content of chromium (Cr) and tantalum (Ta). Therefore, the total content of Cr and Ta is 58 at% or more and 99% or less, preferably 60 at% or more and 99% or less, more preferably 62 at% or more and 99 at% or less, further preferably 62 at% or more and 95 at% or less, and 65 at % To 95 at% is particularly preferable.
The conductive film 4 of the present invention may contain elements other than Cr, Ta, and N as long as the function as the conductive film is not impaired.
However, it is preferable not to contain an element having a higher light absorption coefficient for light having a wavelength of 400 to 800 nm than Cr and Ta. Specific examples of such elements include aluminum (Al) and indium (In).
In the conductive film 4 of the present invention, when the total content of Al and In is 5 at% or less, light absorption in the conductive film is reduced, and the light transmittance at a wavelength of 400 to 800 nm is set to 10% or more. preferable.

The conductive film 4 of the present invention has a nitrogen (N) content in the conductive film of C (at%) and a thickness of the conductive film of t (nm) so that the following formula is satisfied. The N content and the film thickness of the conductive film are set. This satisfies both the sheet resistance value of 250Ω / □ or less and the light transmittance of 10% or more at a wavelength of 400 to 800 nm.
0.15C + 1.68 ≦ t ≦ 0.31C + 11.13
When t <0.15C + 1.68, the sheet resistance value increases and exceeds 250Ω / □.
On the other hand, if t ≧ 0.15C + 1.68, the sheet resistance value is 250 Ω / □ or less. On the other hand, if t> 0.31C + 11.13, the light transmittance at a wavelength of 400 to 800 nm is reduced to 10 %. On the other hand, if t ≦ 0.31C + 11.13, the light transmittance at a wavelength of 400 to 800 nm is 10% or more.

  The film thickness of the conductive film 4 of the present invention is preferably selected from the range of 2 nm to 24 nm so as to satisfy the above inequality. If the film thickness of the conductive film 4 is less than 2 nm, the sheet resistance value increases and it is difficult to make the sheet resistance value 250 Ω / □ or less. On the other hand, when the film thickness of the conductive film 4 exceeds 24 nm, the light transmittance at a wavelength of 400 to 800 nm decreases, and it is difficult to set the light transmittance to 10% or more.

The conductive film 4 of the present invention preferably has a surface roughness (rms) of the conductive film surface of 0.5 nm or less. If the surface roughness of the conductive film is large, the light transmittance may decrease due to light scattering. If the surface roughness (rms) on the surface of the conductive film is 0.5 nm or less, it is preferable for reducing light scattering and making the light transmittance at a wavelength of 400 to 800 nm 10% or more.
Further, if the surface roughness (rms) of the conductive film surface is 0.5 nm or less, the adhesion with the electrostatic chuck is improved, and the generation of particles due to the friction between the electrostatic chuck and the conductive film is prevented. The
The surface roughness (rms) of the conductive film surface is more preferably 0.4 nm or less, and further preferably 0.3 nm or less. The surface roughness (rms) can be evaluated based on the standard of JIS-B0601.

The conductive film 4 in the present invention can be formed by a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. When the conductive film 4 is formed by sputtering, an inert gas containing at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and nitrogen (N ₂ ) and the sputtering method may be performed using a Cr target and / or a Ta target. When the magnetron sputtering method is used, specifically, it may be performed under the following film forming conditions.

In order to form the conductive film 4 by the method described above, specifically, the following film formation conditions may be used.
When forming a CrN film Target: Cr target Sputtering gas: Mixed gas of Ar and N ₂ (N ₂ gas concentration: 3-45 vol%, preferably 5-40 vol%, more preferably 10-35 vol%. Gas) ^{pressure: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1.0 × 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: 2.0-60 nm / min, preferably 3.5-45 nm / min, more preferably 5-30 nm / min
When forming a TaN film Target: Ta target Sputtering gas: Mixed gas of Ar and N ₂ (N ₂ gas concentration: 3-45 vol%, preferably 5-40 vol%, more preferably 10-35 vol%. gas pressure ^{1.0 × 10 -1 Pa~50 × 10 -1} Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1.0 × 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: 2.0-60 nm / min, preferably 3.5-45 nm / min, more preferably 5-30 nm / min

  The EUV mask blank of the present invention may have a configuration other than the configuration shown in FIG. 1, that is, the substrate 1, the reflective layer 2, the absorption layer 3, and the conductive film (back conductive film) 4.

In the EUV mask blank of the present invention, a protective layer may be formed between the reflective layer 2 and the absorbing layer 3. The protective layer protects the reflective layer 2 so that the reflective layer 2 is not damaged by etching when the absorbent layer 3 is etched (usually dry etching) to form a mask pattern on the absorbent layer 3. It is provided for the purpose. Therefore, as the material of the protective layer, a material that is not easily affected by the etching of the absorbing layer 3, that is, the etching rate is slower than that of the absorbing layer 3 and is not easily damaged by the etching 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.
Moreover, when forming a protective layer, the thickness is preferably 1 to 60 nm, and more preferably 1 to 40 nm.

When forming a protective layer, it forms into a film using well-known film-forming methods, such as a magnetron sputtering method and an ion beam sputtering method. When a Ru film is formed by magnetron sputtering, a Ru target is used as a target, and Ar gas (gas pressure: 1.0 × 10 ⁻² Pa to 10 × 10 ⁻¹ Pa) is used as a sputtering gas. It is preferable to form a film so as to have a thickness of 2 to 5 nm at ˜1500 V and a film formation rate of 1.2 to 60 nm / min.

  Even when a protective layer is provided on the reflective layer 2, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, more preferably 63% or more, and 65% or more. Further preferred.

Furthermore, in the EUV mask blank of the present invention, a low reflection layer for inspection light used for inspection of the mask pattern may be formed on the absorption layer 4.
The low reflection layer is formed of a film that exhibits low reflection in the inspection light used for inspection of the mask pattern. When producing an EUV mask, after forming a pattern in the absorption layer, it is inspected whether this pattern is formed as designed. In this mask pattern inspection, an inspection machine that normally uses light of about 257 nm as inspection light is used. That is, the difference in reflectance of light of about 257 nm, specifically, the reflectance between the surface exposed by removing the absorption layer by pattern formation and the surface of the absorption layer remaining without removal by pattern formation. Inspected by difference. Here, the former is a reflective layer surface or a protective layer surface, and is usually a protective layer surface. Therefore, if the difference in reflectance between the reflection layer surface or the protective layer surface and the absorption layer surface 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. When the difference in reflectance between the reflection layer surface or the protective layer surface and the absorption layer surface with respect to the wavelength of the inspection light is small, the contrast at the time of inspection is improved by forming the low reflection layer. When a low reflection layer is formed on the absorption layer, the low reflection layer has a maximum reflectance of a wavelength of 15% or less when the surface of the low reflection layer is irradiated with light in the wavelength region of the inspection light. Is preferably 10% or less, more preferably 5% or less.

In order to achieve the above characteristics, the low reflection layer is preferably made of a material whose refractive index at the wavelength of the inspection light is lower than that of the absorption layer.
The low reflection layer satisfying this characteristic includes at least one selected from the group consisting of tantalum (Ta), palladium (Pd), chromium (Cr), silicon (Si), and hafnium (Hf), oxygen (O), and nitrogen. And at least one selected from the group consisting of (N). Preferable examples of such a low reflection layer include TaPdO layer, TaPdON layer, TaON layer, CrO layer, CrON layer, SiON layer, SiN layer, HfO layer, and HfON layer.
The total content of Ta, Pd, Cr, Si, and Hf in the low reflection layer is preferably 10 to 55 at%, particularly 10 to 50 at%, because the optical characteristics with respect to the wavelength region of the pattern inspection light can be controlled. .
Further, it is preferable that the total content of O and N in the low reflection layer is 45 to 90 at%, particularly 50 to 90 at%, because the optical characteristics with respect to the wavelength region of the pattern inspection light can be controlled. The total content of Ta, Pd, Cr, Si, Hf, O and N in the low reflective layer is preferably 95 to 100 at%, more preferably 97 to 100 at%, and further preferably 99 to 100 at%.

The low reflection layer having the above-described configuration can be formed by performing a sputtering method using a target containing at least one of Ta, Pd, Cr, Si, and Hf. Here, as the target, any of the above-described two or more kinds of metal targets and compound targets can be used.
The use of two or more types of metal targets is convenient for adjusting the constituent components of the low reflection layer. In addition, when using 2 or more types of metal targets, the structural component of an absorption layer can be adjusted by adjusting the input electric power to a target. 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 has a desired composition.

The sputtering method using the above target can be carried out in an inert gas atmosphere in the same manner as the sputtering method for forming the absorption layer.
However, when the low reflection layer contains O, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and O ₂ . When the low reflective layer contains N, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and N ₂ . When the low reflective layer contains O and N, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr and Xe, and O ₂ and N ₂ .

Specific conditions for performing the sputtering method vary depending on the target to be used and the composition of the inert gas atmosphere in which the sputtering method is performed. In any case, the sputtering method may be performed under the following conditions.
The conditions for forming the low reflective layer are shown below, taking as an example the case where the inert gas atmosphere is a mixed gas atmosphere of Ar and O ₂ .
Forming conditions <br/> gas pressure of the low reflective ^{layer: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1.0 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa.
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration: 3 to 80 vol%, preferably 5 to 60 vol%, more preferably 10 to 40 vol%)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.01 to 60 nm / min, preferably 0.05 to 45 nm / min, more preferably 0.1 to 30 nm / min
When using an inert gas other than Ar or a plurality of inert gases, the total concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above. Further, the inert gas atmosphere when containing N ₂ if N ₂ concentration, inert gas atmosphere containing N ₂ and O _2, the same concentration range as the oxygen concentrations above the total concentration.

  In the EUV mask blank of the present invention, the low reflection layer is preferably formed on the absorption layer because the wavelength of the pattern inspection light and the wavelength of the EUV light are different. Therefore, when EUV light (near 13.5 nm) is used as pattern inspection light, it is considered unnecessary to form a low reflection layer on the absorption layer. The wavelength of the inspection light tends to shift to the short wavelength side as the pattern size becomes smaller, and it is conceivable that it will shift to 193 nm and further to 13.5 nm in the future. When the wavelength of the inspection light is 13.5 nm, it is considered unnecessary to form a low reflection layer on the absorption layer.

  In the EUV mask blank of the present invention, on the absorption layer (when the low reflection layer is formed on the absorption layer, on the absorption layer), it is described in JP2009-54899A or JP2009-21582A. A hard mask layer, that is, a layer of a material resistant to the etching conditions of the absorption layer (or the absorption layer and the low reflection layer when the low reflection layer is formed on the absorption layer) may be formed. . By forming such a hard mask layer, the absorption layer (the low reflection layer is formed on the absorption layer) under the etching conditions of the absorption layer (the absorption layer and the low reflection layer when the low reflection layer is formed on the absorption layer) is formed. If formed, the etching selectivity between the absorption layer and the low reflection layer) and the hard mask layer, specifically, the absorption layer (if the low reflection layer is formed on the absorption layer, the absorption layer and the low reflection layer) The ratio of the etching rate of the absorption layer under the etching conditions of the layer) (the etching rate of the absorption layer and the low reflection layer when a low reflection layer is formed on the absorption layer) and the etching rate of the hard mask layer By increasing the thickness, the resist can be thinned.

The present invention will be further described below using examples. In the following, Examples 1 to 7 are Examples, and Examples 8 to 15 are Comparative Examples. In each of Examples 1 to 15, the reflective layer was evaluated by evaluating the sheet resistance value, light transmittance, and film peeling of the conductive film 4 when the conductive film 4 was formed on one surface of the substrate 1. 2, the EUV mask blank and EUV mask of the present invention including the absorption layer 3, the protective layer, the low reflection layer 5 and the like are treated.
Example 1
In this embodiment, the conductive film 4 is formed on one surface of the substrate 1.
As the substrate 1 for film formation, a SiO ₂ —TiO ₂ glass substrate (outer diameter 6 inches (152 mm) square, thickness 6.3 mm) is used. This glass substrate has a thermal expansion coefficient at 20 ° C. of 0.05 × 10 ⁻⁷ / ° C., Young's modulus of 67 GPa, Poisson's ratio of 0.17, and specific rigidity of 3.07 × 10 ⁷ m ² / s ² . This glass substrate is 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 CrN film is formed as a conductive film 4 on one surface of the substrate 1 by using a magnetron sputtering method. The conditions for forming the conductive film 4 (CrN film) are as follows.
Target: Cr target Sputtering gas: mixed gas of Ar and _{N 2 (Ar: 80vol%,} N 2: 20vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 6.1 nm / min
Film thickness: 13nm
Composition analysis of the conductive film 4 (CrN film) The composition of the conductive film 4 (CrN film) was measured using an X-ray photoelectron spectrometer. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 77: 23.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 23 + 1.68 (= 5.13) ≦ 13 ≦ 0.31 × 23 + 11.13 (= 18.26)
The sheet resistance value of the conductive film 4 was measured using a four-probe measuring instrument. The sheet resistance value was 112Ω / □.
Moreover, the result of having measured the light transmittance of wavelength 400-800 nm of the electrically conductive film 4 using the spectrophotometer is shown in FIG. In FIG. 3, the light transmittance was 10% or more in any wavelength region, and in particular, the light transmittance at a wavelength of 532 nm was 21.5%.
Moreover, when the adhesiveness of the board | substrate 1 and the electrically conductive film 4 was evaluated based on JISK5400 (cross-cut method) from the electrically conductive film 4, film peeling was not confirmed but adhesiveness was enough.

Example 2
Example 1 is the same as Example 1 except that the conditions for forming the conductive film 4 (CrN film) are as follows.
Target: Cr target sputtering gas: mixed gas of Ar and N ₂ (Ar: 73 vol%, N ₂ : 27 vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 5.9 nm / min
Film thickness: 20nm
Composition analysis of conductive film 4 (CrN film) The composition of conductive film 4 (CrN film) was measured in the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 69: 31.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 31 + 1.68 (= 6.33) ≦ 20 ≦ 0.31 × 31 + 11.13 (= 20.74)
The sheet resistance value of the conductive film 4 was 73Ω / □.
In any wavelength region of wavelengths 400 to 800 nm, the light transmittance was 10% or more, and in particular, the light transmittance at a wavelength of 532 nm was 11.5%.
The film peeling of the conductive film 4 was not confirmed, and the adhesiveness was sufficient.

Example 3
The same as Example 2 except that the film thickness of the conductive film 4 (CrN film) was 8 nm.
The composition of the conductive film 4 (CrN film) was measured in the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 69: 31.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 31 + 1.68 (= 6.33) ≦ 8 ≦ 0.31 × 31 + 11.13 (= 20.74)
The sheet resistance value of the conductive film 4 was 203Ω / □.
In any wavelength region of wavelengths 400 to 800 nm, the light transmittance was 10% or more, and in particular, the light transmittance at a wavelength of 532 nm was 29.4%.
The film peeling of the conductive film 4 was not confirmed, and the adhesiveness was sufficient.

Example 4
Example 1 is the same as Example 1 except that the conditions for forming the conductive film 4 (CrN film) are as follows.
Target: Cr target Sputtering gas: Mixed gas of Ar and N ₂ (Ar: 95 vol%, N ₂ : 5 vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 6.6 nm / min
Film thickness: 12nm
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 95: 5.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 5 + 1.68 (= 2.43) ≦ 12 ≦ 0.31 × 5 + 11.13 (= 12.68)
The sheet resistance value of the conductive film 4 is 50Ω / □.
In any wavelength region of wavelengths 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 11.9%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 5
The same as Example 4 except that the film thickness of the conductive film 4 (CrN film) is 4 nm.
Composition analysis of the conductive film 4 (CrN film) The composition of the conductive film 4 (CrN film) is measured using an X-ray photoelectron spectrometer. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 95: 5.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 5 + 1.68 (= 2.43) ≦ 4 ≦ 0.31 × 5 + 11.13 (= 12.68)
The sheet resistance value of the conductive film 4 is 150Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 25.8%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 6
Example 1 is the same as Example 1 except that the film formation conditions of the conductive film 4 (CrN film) are as follows.
Target: Cr target Sputtering gas: Mixed gas of Ar and N ₂ (Ar: 64 vol%, N ₂ : 36 vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 5.6 nm / min
Film thickness: 23nm
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 60: 40.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 40 + 1.68 (= 7.68) ≦ 23 ≦ 0.31 × 40 + 11.13 (= 23.53)
The sheet resistance value of the conductive film 4 is 87Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 10.5%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 7
The same as Example 6 except that the thickness of the conductive film 4 (CrN film) is 9 nm.
The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 60: 40.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 40 + 1.68 (= 7.68) ≦ 9 ≦ 0.31 × 40 + 11.13 (= 23.53)
The sheet resistance value of the conductive film 4 is 222Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 30.7%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 8
The same as Example 4 except that the film thickness of the conductive film 4 (CrN film) is 14 nm.
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 95: 5.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 5 + 1.68 (= 2.43) ≦ 14> 0.31 × 5 + 11.13 (= 12.68)
The sheet resistance value of the conductive film 4 is 43Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is less than 10%, and in particular, the light transmittance at a wavelength of 532 nm is 8.5%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 9
The same as Example 4 except that the film thickness of the conductive film 4 (CrN film) is 2 nm.
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 95: 5.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 5 + 1.68 (= 2.43)> 2 ≦ 0.31 × 5 + 11.13 (= 12.68)
The sheet resistance value of the conductive film 4 is 300Ω / □.
In any wavelength region of wavelengths 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 29.2%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 10
The same as Example 1 except that the film thickness of the conductive film 4 (CrN film) was 20 nm.
Composition analysis of conductive film 4 (CrN film) The composition of conductive film 4 (CrN film) was measured in the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) was Cr: N = 77: 23.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 23 + 1.68 (= 5.13) ≦ 20> 0.31 × 23 + 11.13 (= 18.26)
The sheet resistance value of the conductive film 4 was 68Ω / □.
In any wavelength region of wavelengths 400 to 800 nm, the light transmittance was less than 10%, and in particular, the light transmittance at a wavelength of 532 nm was 7.8%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 11
The same as Example 1 except that the film thickness of the conductive film 4 (CrN film) was 4 nm.
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 77: 23.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 23 + 1.68 (= 5.13)> 4 ≦ 0.31 × 23 + 11.13 (= 18.26)
The sheet resistance value of the conductive film 4 is 330Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 32%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 12
The same as Example 6 except that the film thickness of the conductive film 4 (CrN film) is 25 nm.
The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 60: 40.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 40 + 1.68 (= 7.68) ≦ 25> 0.31 × 40 + 11.13 (= 23.53)
The sheet resistance value of the conductive film 4 is 80Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is less than 10%, and in particular, the light transmittance at a wavelength of 532 nm is 7.6%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 13
The same as Example 6 except that the film thickness of the conductive film 4 (CrN film) is 6 nm.
The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 60: 40.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 40 + 1.68 (= 7.68)> 6 ≦ 0.31 × 40 + 11.13 (= 23.53)
The sheet resistance value of the conductive film 4 is 333Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 35%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 14
Example 1 is the same as Example 1 except that the conditions for forming the conductive film 4 (CrN film) are as follows.
Target: Cr target Sputtering gas: Mixed gas of Ar and N ₂ (Ar: 55 vol%, N ₂ : 45 vol%, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 5.0 nm / min
Film thickness: 15nm
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 (CrN film) is measured by the same procedure as in Example 1. The composition ratio (at%) of the conductive film 4 (CrN film) is Cr: N = 57: 43.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 43 + 1.68 (= 8.13) ≦ 15 ≦ 0.31 × 43 + 11.13 (= 24.46)
The sheet resistance value of the conductive film 4 is 1312Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 22.7%.
The film peeling of the conductive film 4 is not confirmed, and the adhesion is sufficient.

Example 15
Example 1 is the same as Example 1 except that the conditions for forming the conductive film 4 are as follows.
Target: Cr target Sputtering gas: Ar gas (gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 7.2 nm / min
Film thickness: 5nm
Composition Analysis of Conductive Film 4 (CrN Film) The composition of the conductive film 4 is measured in the same procedure as in Example 1. The conductive film 4 is a Cr film with 100 at% Cr.
The relationship between the nitrogen content C in the conductive film 4 and the film thickness t is as follows.
0.15 × 0 + 1.68 (= 1.68) ≦ 5 ≦ 0.31 × 0 + 11.13 (= 11.13)
The sheet resistance value of the conductive film 4 is 80Ω / □.
In any wavelength region of wavelengths from 400 to 800 nm, the light transmittance is 10% or more, and in particular, the light transmittance at a wavelength of 532 nm is 22.7%.
Film peeling is confirmed and adhesion is insufficient.

FIG. 2 is a graph showing the relationship between the nitrogen content (C) in the conductive film and the film thickness of the back conductive film in Examples 1 to 15. In FIG. 2, the case where the sheet resistance value is 250Ω / □ is indicated by a thin line. This corresponds to t = 0.15C + 1.68. The case where the light transmittance at a wavelength of 532 nm is 10% is indicated by a bold line. This corresponds to t = 0.31C + 11.13.
In all the examples (Examples 1 to 7), the sheet resistance value was 250Ω / □ or less, and the light transmittance at a wavelength of 532 nm was 10% or more.
In Examples 8, 10, and 12 where t> 0.31C + 11.13, the light transmittance at a wavelength of 532 nm is less than 10%.
In Examples 9, 11, and 13 where t <0.15C + 1.68, the sheet resistance value is more than 250Ω / □.
In Example 14 in which the N content in the conductive film exceeds 42 at%, the sheet resistance value exceeds 250 Ω / □.
In Example 15 in which the N content in the conductive film was 0 at%, the adhesion was evaluated based on JIS K5400 (cross-cut method). As a result, film peeling was confirmed, and the adhesion was insufficient.

1: Substrate 2: Reflective layer (multilayer reflective film)
3: Absorbing layer 4: (Back) conductive film

Claims (8)

A reflective mask blank for EUV lithography, in which a reflective layer that reflects EUV light and an absorbing layer that absorbs EUV light are formed in this order on one surface of the substrate, and a conductive film is formed on the other surface of the substrate Because
The conductive film contains chromium (Cr) and nitrogen (N),
The content of Cr in the conductive film is 58 at% or more and 99 at% or less, and the content of N is 1 at% or more and 42 at% or less,
A reflective mask blank for EUV lithography, wherein the N content in the conductive film is C (at%) and the film thickness of the conductive film is t (nm), and the following formula is satisfied.
0.15C + 1.68 ≦ t ≦ 0.31C + 11.13 The reflective mask blank for EUV lithography according to claim 1 , wherein the film thickness of the conductive film is 2 nm or more and 24 nm or less. The reflective mask blank for EUV lithography according to claim 1 or 2 , wherein the conductive film surface has a surface roughness (rms) of 0.5 nm or less. The reflective mask blank for EUV lithography according to any one of claims 1 to 3 , wherein the total content of aluminum (Al) and indium (In) in the conductive film is 5 at% or less. The reflective mask blank for EUV lithography according to any one of claims 1 to 4 , wherein a sheet resistance value of the conductive film is 250 Ω / □ or less. The reflective mask blank for EUV lithography according to any one of claims 1 to 5 , wherein the conductive film has a light transmittance of 10% or more at a wavelength of 400 to 800 nm. A protective layer is formed between the reflective layer and the absorbing layer to protect the reflective layer when forming a pattern on the absorbing layer.
The protective layer is, as a constituent material of Ru or a Ru compound, EUV lithography reflective mask blank according to any one of claims 1-6. Claim. 1 to 7 EUV lithography reflective mask formed by patterning a reflective mask blank for EUV lithography according to any one of.

Images