JP7006078B2 - Reflective mask blank, and reflective mask - Google Patents

Description

The present invention relates to a reflective mask blank used for manufacturing semiconductors and the like, and a reflective mask formed by forming a mask pattern on an absorption film of the reflective mask blank.

Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a transfer technique for a fine pattern necessary for forming an integrated circuit composed of a fine pattern on a Si substrate or the like. However, while the miniaturization of semiconductor devices is accelerating, the limits of conventional photolithography methods are approaching. In the case of the photolithography method, the resolution limit of the pattern is about 1/2 of the exposure wavelength, and it is said that even if the immersion method is used, it is about 1/4 of the exposure wavelength. Even if the method is used, the limit is expected to be about 45 nm. Therefore, EUV lithography, which is an exposure technique using EUV light having a shorter wavelength than the ArF laser, is promising as an exposure technique for 45 nm or more. As used herein, EUV light refers to light rays having a wavelength in the soft X-ray region or vacuum ultraviolet region, specifically, light rays having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ± 0.3 nm.

EUV light is easily absorbed by any substance, and the refractive index of the substance is close to 1 at this wavelength, so that a refraction optical system such as conventional photolithography using visible light or ultraviolet light cannot be used. For this reason, EUV optical lithography uses a reflective optical system, that is, a reflective photomask and a mirror.

The reflective mask blank is a laminate before patterning used for manufacturing a reflective photomask, and a reflective layer that reflects EUV light on a substrate such as glass and an absorbent film that absorbs EUV light are in this order. It has a structure formed by.
As the reflective layer, the low refractive index layer having a low refractive index with respect to the EUV light and the high refractive index layer having a high refractive index with respect to the EUV light are alternately laminated so that the EUV light is applied to the layer surface. A multilayer reflective film having an increased light refractive index when irradiated is usually used. A molybdenum (Mo) layer is usually used as the low refractive index layer of the multilayer reflective film, and a silicon (Si) layer is usually used as the high refractive index layer.
As the absorbing film, a material having a high absorption coefficient for EUV light, specifically, for example, a material containing tantalum (Ta) as a main component is used (see Patent Documents 1 to 5).

Japanese Patent No. 5507876 Japanese Unexamined Patent Publication No. 2012-33715 Japanese Unexamined Patent Publication No. 2015-84447 Japanese Unexamined Patent Publication No. 2010-206156 Japanese Patent No. 3806702

When producing a reflective photomask from a mask blank, a desired pattern is formed on the absorbent film of the mask blank. When forming a pattern on the absorbent film, an etching process, usually a dry etching process, is used. It is preferable that the etching rate is sufficient during the dry etching process because the etching selectivity at the time of pattern formation is improved. When the etching selection ratio is improved, the time required for patterning is shortened, productivity is improved, and damage to the multilayer reflective film due to the etching process is reduced.

An object of the present invention is to provide a reflective mask blank having an absorbent film having a sufficient etching rate during a dry etching process, and a reflective mask.

As a result of diligent studies to achieve the above object, the present invention has sufficient etching during the dry etching process when the crystal state of the absorption film containing Ta and nitrogen (N) is set to a specific state. We have found that we can achieve speed.
The present invention has been made based on the above findings, and is a reflective mask blank including a multilayer reflective film that reflects EUV light and an absorbent film that absorbs EUV light on a substrate in this order, and is the absorption type mask blank. The film is a tantalum-based material film containing a tantalum-based material.
In the X-ray diffraction pattern, the peak diffraction angle 2θ of the peak derived from the tantalum material is 36.8 deg or more, and the half width of the peak derived from the tantalum material is 1.5 deg or more. Provided is a reflective mask blank characterized by.

In the reflective mask blank of the present invention, the tantalum-based material film preferably contains 10.0 to 35.0 at% of nitrogen atoms.

In the reflective mask blank of the present invention, the tantalum-based material film preferably contains 0.05 at% or more of krypton atoms.

In the reflective mask blank of the present invention, it is preferable that a protective film is provided on the multilayer reflective film, and the etching selectivity between the absorption film and the protective film is 45 or more with respect to the dry etching treatment with chlorine gas. ..

In the reflective mask blank of the present invention, the protective film is preferably a ruthenium-based material film containing a ruthenium-based material.

The present invention also provides a reflective mask in which a pattern is formed on the absorbent film of the reflective mask blank of the present invention.

Since the reflective mask blank of the present invention has an absorbing film having a sufficient etching rate during the dry etching process, the etching selectivity at the time of pattern formation is high.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the reflective mask blank of the present invention. FIG. 2 is a diagram showing X-ray diffraction patterns of Samples 1 to 4 and Samples 6 and 7. FIG. 3 is a TEM observation result of the sample 7. FIG. 4 is a TEM observation result of the sample 4.

Hereinafter, the reflective mask blank of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing one embodiment of the reflective mask blank of the present invention. In the reflective mask blank 1 shown in FIG. 1, a multilayer reflective film 12 that reflects EUV light and an absorption film 14 that absorbs EUV light are formed on the substrate 11 in this order. A protective film 13 for protecting the multilayer reflective film 12 when forming a pattern on the absorbent film 14 is formed between the multilayer reflective film 12 and the absorbent film 14. The back surface conductive film 15 is formed on the back surface side of the substrate 11, that is, the back surface side on which the multilayer reflective film 12, the protective film 13, and the absorption film 14 are formed.
Hereinafter, individual components of the mask blank of the present invention will be described.
In the reflective mask blank of the present invention, in the configuration shown in FIG. 1, only the substrate 11, the multilayer reflective film 12, and the absorbent film 14 are indispensable, and the protective film 13 and the back surface conductive film 15 are arbitrary components. Is.
Hereinafter, individual components of the reflective mask blank 1 will be described.

The substrate 11 is required to satisfy the characteristics as a substrate for a reflective mask blank. Therefore, the substrate 11 preferably has a low coefficient of thermal expansion (specifically, the coefficient of thermal expansion at 20 ° C. is 0 ± 0.05 × 10 ^-7 / ° C., and particularly preferably 0 ± 0.03 × 10 ⁻ . It is preferably ⁷ / ° C.) and has excellent smoothness, flatness, and resistance to a cleaning solution used for cleaning a mask blank or a photomask after pattern formation. Specifically, as the substrate 11, glass having a low thermal expansion coefficient, for example, SiO ₂ -TiO ₂ system glass or the like is used, but the substrate 11 is not limited to this, and crystallized glass, quartz glass, silicon, etc. in which β quartz solid solution is precipitated can be used. A substrate such as metal can be used.
Since the substrate 11 has a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less, high reflectance and transfer accuracy can be obtained in the reflective photomask after pattern formation. Is preferable.
The size and thickness of the substrate 11 are appropriately determined by the design value of the mask and the like. In the examples shown later, SiO ₂ -TiO ₂ system glass having an outer diameter of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm) was used.
It is preferable that there are no defects on the surface of the substrate 11 on the side where the multilayer reflective film 12 is formed. However, even if they are present, the depth of the concave defects and the height of the convex defects are 2 nm or less and these concave defects so that the phase defects do not occur due to the concave defects and / or the convex defects. It is preferable that the half-value width of the defect and the convex defect is 60 nm or less.

The multilayer reflective film 12 achieves high EUV light reflectance by alternately laminating a high refractive index layer and a low refractive index layer a plurality of times. In the multilayer reflective film 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 the 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 multilayer reflective film 12 is not particularly limited as long as it has the desired characteristics as the multilayer reflective film of the reflective mask blank. Here, a characteristic particularly required for the multilayer reflective film 12 is a high EUV ray reflectance. Specifically, when the surface of the multilayer reflective film 12 is irradiated with light rays in the wavelength region of 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. , 65% or more is more preferable. Further, even when the protective film 13 is provided on the multilayer reflective film 12, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, preferably 65% or more. More preferred.

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

Each layer constituting the multilayer reflective film 12 may be formed into a desired thickness by using a well-known film forming method such as a magnetron sputtering method or an ion beam sputtering method. For example, when a Si / Mo multilayer reflective film is formed by using the ion beam sputtering method, a 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. Using ² Pa), a Si film is formed so that the ion acceleration voltage is 300 to 1500 V, the film formation rate is 1.8 to 18 nm / min, and the thickness is 4.5 nm, and then the Mo target is used as the target. Using Ar gas (gas pressure 1.3 × 10 ⁻² Pa to 2.7 × 10 ⁻² Pa) as the sputtering gas, the ion acceleration voltage is 300 to 1500 V, and the film formation speed is 1.8 to 18 nm / min. It is preferable to form a Mo film so as to have a thickness of 2.3 nm. With this as one cycle, the Si / Mo multilayer reflective film is formed by laminating the Si film and the Mo film for 40 to 50 cycles.

In order to prevent the surface of the multilayer reflective film 12 from being oxidized, it is preferable that the uppermost layer of the multilayer reflective film 12 is a layer of a material that is not easily oxidized. The layer of the material which is hard to be oxidized functions as a cap layer of the multilayer reflective film 12. A Si layer can be exemplified as a specific example of a layer of a material that does not easily oxidize and functions as a cap layer. When the multilayer reflective film 12 is a Si / Mo film, the uppermost layer can be made to function as a cap layer by making the uppermost layer a Si layer. In that case, the film thickness of the cap layer is preferably 11 ± 2 nm.

The protective film 13 is arbitrarily provided for the purpose of protecting the multilayer reflective film 12 so that the multilayer reflective film 12 is not damaged by the etching process when the pattern is formed on the absorbing film 14 by etching treatment, usually dry etching treatment. It is a component. However, from the viewpoint of protecting the multilayer reflective film 12, it is preferable to form the protective film 13 on the multilayer reflective film 12.

As the material of the protective film 13, a substance that is not easily affected by the etching treatment of the absorption film 14, that is, the etching rate is slower than that of the absorption film 14, and is not easily damaged by this etching treatment is selected.
Further, for the protective film 13, select a substance having a high EUV reflectance for the protective film 13 itself so as not to impair the EUV reflectance of the multilayer reflective film 12 even after the protective film 13 is formed. Is preferable.
As the protective film 13, a ruthenium-based material film containing a ruthenium-based material is preferable. In the present specification, the term ruthenium-based material refers to Ru and Ru compounds (RuB, RuSi, etc.). The content of Ru in the ruthenium-based material film is preferably 50 at% or more, more preferably 70 at% or more, further preferably 90 at% or more, and particularly preferably 95 at% or more.

When the protective film 13 is formed on the multilayer reflective film 12, the thickness of the protective film 13 is preferably 1 to 10 nm because the EUV reflectance is increased and the etching resistance property can be obtained. The thickness of the protective film 13 is more preferably 1 to 5 nm, still more preferably 2 to 4 nm.

When the protective film 13 is formed on the multilayer reflective film 12, the protective film 13 can be formed by using a well-known film forming method such as a magnetron sputtering method or an ion beam sputtering method.
When the Ru film is formed as the protective film 13 by using the ion beam sputtering method, the Ru target may be used as the target and discharged in an argon (Ar) atmosphere. Specifically, ion beam sputtering may be performed under the following conditions.
Sputtering gas: Ar (gas pressure: 1.3 x 10 ^-2 Pa to 2.7 x 10 ^-2 Pa)
Ion acceleration voltage: 300-1500V
Film formation speed: 1.8 to 18.0 nm / min

A particularly required property of the absorbent film 14 is its extremely low EUV reflectance. Specifically, when the surface of the absorption film 14 is irradiated with light rays in the wavelength region of EUV light, the maximum light reflectance near the wavelength of 13.5 nm is preferably 2.0% or less, preferably 1.0% or less. Is more preferable, 0.5% or less is further preferable, and 0.1% or less is particularly preferable.

In order to achieve the above characteristics, the absorption film 14 is made of a material having a high absorption coefficient of EUV light. In the reflective mask blank 1 of the present invention, a tantalum-based material film containing a tantalum-based material is used as a material having a high absorption coefficient of EUV light constituting the absorption film 14. The reason for using the tantalum-based material film is that it is chemically stable and that etching is easy when the pattern of the absorbent film is formed. In the present specification, the term tantalum-based material refers to tantalum (Ta) and a Ta compound.

It is preferable that the tantalum-based material film contains Ta and nitrogen (N) because it can suppress the crystallization of Ta and prevent the crystals from becoming large and the surface roughness from becoming high.
When the tantalum-based material film contains Ta and N, the content of N atoms is 10.0 to 35.0 at%, which satisfies the conditions described later in the X-ray diffraction pattern of the absorption film 14, and also It is preferable in order to increase the etching selectivity, more preferably 10.0 to 25.0 at%, further preferably 10.5 to 18.0 at%, and particularly preferably 11.0 to 16.0 at%.

When the tantalum-based material film contains Ta and N, hafnium (Hf), silicon (Si), zirconium (Zr), titanium (Ti), germanium (Ge), boron (B), tin (Sn), and nickel. It may contain at least one element selected from (Ni), cobalt (Co) and hydrogen (H). When these elements are contained, the total content in the tantalum-based material film is preferably 10 at% or less.

The absorption film 14, which is a tantalum-based material film, has a peak derived from the tantalum-based material in the pattern of X-ray diffraction. The reflective mask blank 1 of the present invention has a sufficient etching rate during the dry etching process when the peak derived from the tantalum-based material satisfies the conditions 1 and 2 shown below.
Condition 1: The peak diffraction angle 2θ of the peak is 36.8 deg or more.
Condition 2: The half width of the peak is 1.5 deg or more.
In the present specification, the half width is also referred to as FWHM.

When the peak diffraction angle 2θ of the peak is less than 36.8 deg, the ratio of the amorphous phase in the crystal phase becomes high, and the etching rate during the dry etching process decreases. On the other hand, when the diffraction angle 2θ is 36.8 deg or more, the mixed phase state of the amorphous phase and the microcrystalline phase in the crystal phase becomes appropriate, and the etching easily proceeds at the phase interface, so that the etching rate becomes high.
The peak diffraction angle 2θ of the peak is preferably in the range of 36.8 deg to 40.0 deg, and more preferably in the range of 37.0 deg to 39.0 deg.

When the half width of the peak is less than 1.5 deg, the crystallinity of the tantalum-based material film becomes high, so that coarse crystal grains are generated on the surface of the tantalum-based material film. Coarse crystal grains on the surface of the tantalum-based material film are detected as adhering foreign substances during defect inspection, making it difficult to distinguish them from the adhering foreign substances that should be originally inspected, which may reduce the defect inspection accuracy. In addition, it becomes difficult to uniformly etch the absorbent film, and the surface roughness after etching may become rough.
The half width of the peak is preferably 2.5 deg to 6.0 deg, and more preferably 3.0 deg to 5.0 deg.

The absorption film 14 satisfying the above conditions 1 and 2 has a sufficient etching rate during the dry etching process, and is a multilayer reflective film (when a protective film is not formed on the multilayer reflective film) or a protective film (multilayer). When a protective film is formed on the reflective film), the etching selectivity is high. For example, the etching rate is high during the dry etching process using a chlorine-based gas as the etching gas, and the etching selection ratio with the protective film 13 is 45 or more. In the present specification, the etching selectivity can be calculated using, for example, the following equation.
Etching selectivity = (etching rate of absorbent film 14) / (etching rate of protective film 13)
The etching selection ratio in the dry etching process using a chlorine-based gas as the etching gas is preferably 45 or more, more preferably 50 or more, further preferably 55 or more, and particularly preferably 60 or more.

The film thickness of the absorbent film 14 is preferably 5 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, and particularly preferably 35 nm or more.
On the other hand, if the film thickness of the absorption film 14 is too large, the accuracy of the pattern formed on the absorption film 14 may decrease, so 100 nm or less is preferable, 90 nm or less is more preferable, and 80 nm or less is further preferable.
The film thickness of the absorption film 14 can be reduced by using the principle of phase shift or by including an element having a high absorption coefficient such as Sn, Ni, Co, etc. in the absorption film 14.

As the absorbent film 14, a well-known film forming method such as a magnetron sputtering method or a sputtering method such as an ion beam sputtering method can be used.
When the TaN layer is formed as the absorption membrane 14, when the magnetron sputtering method is used, the TaN layer can be formed by using a Ta target and discharging the target in a nitrogen (N ₂ ) atmosphere diluted with Ar. ..

In order to form the TaN layer as the absorption film 14 by the above-exemplified method, specifically, it may be carried out under the following film forming conditions.
Sputtering gas: A mixed gas of rare gas and N ₂ (N ₂ gas concentration 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%. Gas pressure 0.5 × 10 ^-1 Pa to 10 × 10 ^-1 Pa, preferably 0.5 × 10 ^-1 Pa to 5 × 10 ^-1 Pa, more preferably 0.5 × 10 ^-1 Pa to 3 × 10 ^-1 Pa.)
Input power (for each target): 30 to 2000 W, preferably 50 to 1500 W, more preferably 80 to 1000 W.
Film formation rate: 2.0 to 60 nm / min, preferably 3.5 to 45 nm / min, more preferably 5 to 30 nm / min.

In the above, it is preferable to use krypton (Kr) as a rare gas in the sputtering gas because it can prevent film distortion during formation of the absorbent film 14 and suppress deformation of the substrate.
The absorption film 14 formed by using krypton (Kr) as a rare gas in the sputtering gas contains 0.05 at% or more of Kr atoms.

For the back surface conductive film 15, the electrical conductivity and thickness of the constituent materials are selected so that the sheet resistance is 100 Ω / □ or less. The constituent material of the back surface conductive film 15 can be widely selected from those described in known documents. For example, it is selected from the group consisting of the high dielectric constant material layer described in JP-A-2003-501823 and Re-Table 2008/072706, specifically, silicon, TiN, molybdenum, chromium (Cr), CrN, and TaSi. The material layer is mentioned. The back surface conductive film can be formed by a dry film forming method, specifically, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, and a dry film forming method such as a vacuum vapor deposition method. For example, when the CrN film is formed by the magnetron sputtering method, magnetron sputtering may be performed with the target as the Cr target and the sputter gas as a mixed gas of Ar and N ₂ , and specifically, it is carried out under the following film forming conditions. do it.
Target: Cr Target Sputter gas: Mixed gas of Ar and N ₂ (N ₂ gas concentration 10 to 80 vol%. Gas pressure 0.02 Pa to 5 Pa)
Input power: 30-2000W
Film formation rate: 2.0-60 nm / mim

The reflective mask blank of the present invention may have components other than the above. For example, a low-reflection layer or a hard mask for inspection light used for inspection of a mask pattern may be formed on the absorbent film.
Examples of the low-reflection layer include materials containing at least one element among Ta, Hf, Si, Zr, Ti, Ge, B, Sn, Ni, Co, N, H, and O. For example, TaO, TaON, TaONH, TaHfO, TaHfON and the like can be mentioned.
Examples of the material of the hard mask layer include materials containing at least one element among Cr, Ru, Zr, In, Si, N, H, and O. For example, CrN, CrON, Ru, SiO ₂ , SiON, Si _{3N 4 ,} SiC and the like can be mentioned.

Hereinafter, the present invention will be further described with reference to examples.
Examples 1 to 5 are examples, and examples 6 and 7 are comparative examples.

(Example 1)
A reflective mask blank was manufactured by the following method.
First, as a substrate, a glass substrate (SiO ₂ -TiO ₂ system) having a length of 152.4 mm, a width of 152.4 mm, and a thickness of 6.3 mm was prepared.
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 . The glass substrate was polished and used so that the surface roughness (root mean square height Sq) of the main surface was 0.15 nm or less and the flatness was 100 nm or less.
Next, a back surface conductive film was formed on one surface (second main surface) of the glass substrate. The back surface conductive film was a CrN film, and a film was formed so as to have a thickness of about 100 nm by a magnetron sputtering method. The sheet resistance of the back surface conductive film is 100Ω / □.
Next, using an electrostatic chuck, the glass substrate was fixed in the film forming chamber by an electrostatic adsorption method via a back surface conductive film. In this state, a multilayer reflective film was formed on the first main surface of the glass substrate.
An ion beam sputtering method was used to form a Mo / Si multilayer reflective film by alternately forming a Mo layer having a thickness of 2.3 nm and a Si layer having a thickness of 4.5 nm 50 times each. ..
For the formation of the Mo layer, an ion beam sputtering was performed in an Ar gas atmosphere using a Mo target (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the film forming speed was 3.84 nm / min.
On the other hand, for the formation of the Si layer, a boron-doped Si target was used, and ion beam sputtering was performed in an Ar gas atmosphere (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the film forming speed was 4.62 nm / min.
The total thickness (target value) of the multilayer film is (2.3 nm + 4.5 nm) × 50 times = 340 nm. The uppermost layer of the multilayer reflective film was a Si layer.
Next, a protective film was formed on the reflective layer by the ion beam sputtering method.
The protective film was a Ru layer, and ion beam sputtering was performed in an Ar gas atmosphere using a Ru target (gas pressure: 0.02 Pa). The applied voltage was 700 V, and the film forming speed was 3.12 nm / min. The film thickness of the protective film was 2.5 nm.
Next, an absorption film was formed on the protective film by the magnetron sputtering method.
The absorption membrane was a TaN layer, and magnetron sputtering was performed using a Ta target in an atmosphere of a mixed gas of Kr and N ₂ (Kr = 95 vol%, N ₂ = 5 vol%). The film forming speed was 7.7 nm / min, and the film thickness was 75 nm.
As a result, Sample 1 for evaluating the characteristics of the absorbent film of the reflective mask blank according to Example 1 was obtained.
Next, a low reflection layer was formed on the absorption film by a magnetron sputtering method.
The low-reflection layer is a TaON layer, and magnetron sputtering is performed using a Ta target in an atmosphere of a mixed gas of Ar, O ₂ , and N ₂ (Ar = 60 vol%, O ₂ = 30 vol%, N ₂ = 10 vol%). Was carried out. The film forming speed was 1.32 nm / min. The film thickness of the low reflection layer was 5 nm.
As a result, the reflective mask blank according to Example 1 was manufactured.

(Example 2)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in this Example 2, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from the case of Example 1. More specifically, the mixing ratio (volume ratio) of Kr and N ₂ in the mixed gas was set to 93: 7. Other conditions are the same as in Example 1.
Similar to Example 1, a sample for evaluating the characteristics of the absorbent film of the reflective mask blank having a film formed up to the absorbent film was prepared. This is referred to as "sample 2" (hereinafter, the same applies).

(Example 3)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in Example 3, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from those in Example 1. More specifically, the mixing ratio (volume ratio) of Kr and N ₂ in the mixed gas was set to 91: 9. Other conditions are the same as in Example 1.

(Example 4)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in this Example 4, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from the case of Example 1. More specifically, the mixing ratio (volume ratio) of Kr and N ₂ in the mixed gas was set to 89:11. Other conditions are the same as in Example 1.

(Example 5)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in this Example 5, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from the case of Example 1. More specifically, a mixed gas of Ar, Kr, and N ₂ was used as the mixed gas. The mixing ratio of Ar, Kr, and N ₂ was 54:38: 8. Other conditions are the same as in Example 1.

(Example 6)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in this example, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from the case of Example 1. More specifically, a mixed gas of Ar, Kr, and N ₂ was used as the mixed gas. The mixing ratio of Ar, Kr, and N ₂ was 67:17:16. Other conditions are the same as in Example 1.

(Example 7)
A reflective mask blank was manufactured by the same method as in Example 1.
However, in this example, the conditions for forming the TaN layer as the absorption film by the magnetron sputtering method were changed from the case of Example 1. More specifically, the mixing ratio (volume ratio) of Kr and N ₂ in the mixed gas was set to 94: 6. Other conditions are the same as in Example 1.

(evaluation)
The following evaluations were performed using each sample produced as described above.

(XRD measurement)
In-plane XRD measurement was performed using an X-ray diffractometer (model: ATX-G, manufacturer: manufactured by Rigaku Co., Ltd.). At the time of measurement, the one in which the width limiting slit 1 mm and the vertical limiting slit 10 mm are overlapped from the incident side of the X-ray and the one in which the width limiting slit 0.1 mm and the vertical limiting slit 10 mm are overlapped are arranged at two places, and divergence is performed between them. A solar slit with an angle of 0.48 ° was placed. A solar slit with a divergence angle of 0.41 ° was placed on the light receiving side. A Cu Kα ray (wavelength: 1.5418 Å) with an output of 50 kV-300 mA was used as the X-ray source, and the data was measured under the conditions of an incident angle of 0.6 °, a step width of 0.05 °, and a scan speed of 1 ° / min. Got
X-ray analysis software (model: PDXL2, manufacturer: manufactured by Rigaku Co., Ltd.) was used for the analysis of the measurement data. Data processing is smoothing by B-Spline (Χ threshold: 1.50), background removal (fitting method), Kα2 removal (intensity ratio 0.497), peak search (second derivative method, σ cut value: 3). .00), profile fitting (fitting to the measured data, peak shape: split type Voigt function) was performed, and a diffraction angle of 2θ and a half width were obtained.
FIG. 2 is a diagram showing X-ray diffraction patterns of Samples 1 to 4 and Samples 6 and 7. In FIG. 2, a fixed value is added to the value of the intensity (cps) of the X-ray diffraction peak of each sample, and the intensity of the X-ray diffraction peak of each sample is shifted to facilitate observation of the peak shape. Therefore, the scale on the vertical axis is not an absolute value of intensity but a mere intensity (cps).

(Etching speed evaluation)
Reactive ion etching was performed using an etching device (model: CE-300R, manufacturer: ULVAC, Inc.) in an atmosphere of a mixed gas of Cl ₂ and He (Cl ₂ = 20 vol%, He = 80 vol%). .. After that, using an X-ray reflectance measuring device (model: SmartLab HTP, manufacturer: manufactured by Rigaku Co., Ltd.), the thickness (nm) of the absorbed film and protective film after etching is measured, and the absorbent film and protective film are measured. Etching rate (nm / min) was obtained. The etching selectivity was determined from the etching rate of the absorbent film (absorbent film etching rate / protective film etching rate) with respect to the etching rate of the protective film. The etching rate of the protective film is 0.047 nm / sec.

(Membrane composition evaluation)
Using a Rutherford backscattering analyzer (model: RBS, manufacturer: Kobelco Kaken Co., Ltd.), Ta amount (at%), N amount (at%), Kr amount (at%) in the membrane of samples 1 to 7 Got In addition, since the value of the amount of N in the film was small for the samples 1 to 3 and 7, the Rutherford backscattering analyzer could not perform a quantitative evaluation with high accuracy. Therefore, the Ta amount (at%) and the N amount (at%) were measured using an electron probe microanalyzer (model: JXA-8500F, manufacturer: JEOL Ltd.). The measurement by the electron probe microanalyzer has an acceleration voltage of 4 kV, an irradiation current of 30 nA, a beam diameter of 100 μm, N uses LDE1H as a spectroscopic crystal, Kα ray measurement, and Ta uses PETJ as a spectroscopic crystal, and Mα ray measurement is performed. went. The amount of Ta (at%) and the amount of N (at%) were quantified by the calibration curve method, normalized to 100 wt% for Ta and N, and then converted to at%. As standard samples, two points were used: sample 4 for which the amount of N (at%) was determined by Rutherford backscattering analysis, and Ta film containing no N.

(Defective inspection)
Each sample was inspected for defects according to the following procedure.
A defect inspection device using a visible light laser (model: M1350, manufacturer: Lasertec) was used to inspect the surface of each sample on the absorption layer side. The evaluation area was a range of 132 mm × 132 mm.
When the sample 7 was inspected with a defect inspection device, 500 or more defects of 100 nm or less were detected, but when the surface was observed with a scanning electron microscope (model: Ultra60, manufacturer: Carl Zeiss), actual defects were present. No actual defects were confirmed. From this, it was found that what was detected as a defect of 100 nm or less by the defect inspection device was a pseudo defect due to the surface roughness. The presence of such pseudo-defects hinders the accurate evaluation of real defects.
For samples in which a large number of pseudo-defects were detected and accurate defect inspection was difficult, the inspectability was judged as B.
On the other hand, for samples that can be accurately inspected for defects, the inspectability was judged as A.

For Sample 4 and Sample 7, TEM observation was performed according to the following procedure.
The TEM (hereinafter, also referred to as transmission electron microscope) observation sample was obtained by polishing from the substrate side on which the absorption film was formed to prepare a flaky sample containing only the absorption film. For polishing from the substrate side, a mechanical polishing machine (model: Beta Grinder Polisher, manufacturer: manufactured by Buhra) and an ion polishing machine (model: precision ion polishing system Model 691, manufacturer: manufactured by Gatan) were used. A thin-section sample containing only the absorption film was observed from the plane direction of the absorption film at an acceleration voltage of 200 kV using a transmission electron microscope (model: JEM-2010F, manufacturer: manufactured by JEOL Ltd.). FIG. 3 shows the TEM observation result of the sample 7, and FIG. 4 shows the TEM observation result of the sample 4. It can be seen that the surface of the sample 7 is remarkably rough.

Further, when samples were manufactured and evaluated under the same conditions as in Example 1 with film thicknesses of 50 nm and 58 nm, the performance was equivalent to that of sample 1.

サンプル１～５は、いずれも、塩素ガスによる吸収膜のドライエッチング処理時におけるエッチング速度が速く、保護膜とのエッチング選択比が高かった。これに対し、回折角２θが３６．８ｄｅｇ未満のサンプル６は、塩素ガスによる吸収膜のドライエッチング処理時におけるエッチング速度が遅く、保護膜とのエッチング選択比が低かった。一方、半値幅が１．５ｄｅｇ未満のサンプル７は、図３に示すように吸収膜表面に粗大な結晶粒が生じていた。また、サンプル７は検査性の評価結果がＢ判定であった。サンプル１～７は、いずれも、１３．５ｎｍ付近のＥＵＶ反射率の値が１．５％以下となり、吸収膜に求められるＥＵＶ吸収特性を満たしていた。 The results are shown in the table below.

In each of the samples 1 to 5, the etching rate at the time of the dry etching treatment of the absorption film by chlorine gas was high, and the etching selection ratio with the protective film was high. On the other hand, in the sample 6 having a diffraction angle 2θ of less than 36.8 deg, the etching rate during the dry etching treatment of the absorption film by chlorine gas was slow, and the etching selectivity with the protective film was low. On the other hand, in the sample 7 having a half width of less than 1.5 deg, coarse crystal grains were formed on the surface of the absorption film as shown in FIG. Further, in the sample 7, the evaluation result of the inspectability was B judgment. In each of the samples 1 to 7, the EUV reflectance value near 13.5 nm was 1.5% or less, which satisfied the EUV absorption characteristics required for the absorption film.

1: EUV mask blank 11: Substrate 12: Reflective layer (multilayer reflective film)
13: Protective layer 14: Absorbent film 15: Backside conductive film

Claims (4)

A reflective mask blank comprising a multilayer reflective film that reflects EUV light on a substrate and an absorbent film that absorbs EUV light in this order, wherein the absorbent film is a tantalum-based material film containing a tantalum-based material.
In the X-ray diffraction pattern, the peak diffraction angle 2θ of the peak derived from the tantalum material is 36.8 deg or more, and the half width of the peak derived from the tantalum material is 1.5 deg or more. It is a reflective mask blank characterized by
The tantalum-based material film contains tantalum atoms, nitrogen atoms, and krypton atoms.
The tantalum-based material film contains 10.0 to 35.0 at% of nitrogen atoms.
A reflective mask blank in which the tantalum-based material film contains 0.05 at% or more of krypton atoms. The reflective mask blank according to claim 1 , wherein a protective film is provided on the multilayer reflective film, and the etching selectivity between the absorbent film and the protective film is 45 or more with respect to a dry etching process using chlorine gas. The reflective mask blank according to claim 2 , wherein the protective film is a ruthenium-based material film containing a ruthenium-based material. A reflective mask in which a pattern is formed on the absorbent film of the reflective mask blank according to any one of claims 1 to 3 .

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