JPH08264419A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE: To provide a manufacturing method of an X-ray mask with an X-ray absorbing film having extremely small internal stress of an X-ray absorber film besides uniform stress distribution inside the face and being excellent in fine workability. CONSTITUTION: In a method of manufacturing an X-ray mask provided with X-ray transmitting films 2a, 2b and an X-ray absorbing film 3a containing tantalum and boron in the range of atomic rations (Ta/B) 8.5/1.5 to 7.5/2.5, X-ray transmitting films 2a, 2b are formed on both faces of a substrate 1a and an X-ray absorption film 3a is formed on the X-ray transmitting film 2a by a sputtering method using Xe as sputtering gas followed by annealing treatment. Here, the X-ray transmitting film 2a has a surface roughness 0.2-20nm (Ra: central line average roughness).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an X-ray mask used in X-ray lithography, and more specifically to an X-ray mask in which the internal stress of an X-ray absorber film that affects the pattern position accuracy is precisely controlled. Manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method for transferring a fine pattern using visible light or ultraviolet light as an electromagnetic wave for exposure has been used as a technique for forming an integrated circuit having a fine pattern on a silicon substrate or the like. Has been used. However, in recent years, along with the progress of semiconductor technology, super L
High integration of semiconductor devices such as SI has progressed remarkably, and with such a background, transfer technology of high-precision fine patterns exceeding the transfer limit of visible light and ultraviolet light used in the conventional photolithography method has been developed. I came to be requested. In order to transfer such a fine pattern, an X-ray lithography method used as an X-ray exposure electromagnetic wave having a shorter wavelength than visible light or ultraviolet rays has been attempted.

In an X-ray mask used for X-ray lithography, an X-ray absorbing film has a fine pattern and is composed of an X-ray transmitting film and an X-ray absorbing film, which are supported by a silicon wafer. . Here, it is needless to say that a material having a large X-ray grade yield must be used for the X-ray absorbing film, but the following requirements must be satisfied.

First, the internal stress is small.
This is because if the internal stress is large, the stress of the film causes a positional shift of the absorber pattern, and the pattern transfer accuracy cannot be ensured. For example, when a positional accuracy of 30 nm (3σ) or less is required in the design rule of 0.2 μm or less, the X-ray absorber film is required to have a small internal stress of 10 MPa or less. Further, this internal stress needs to be uniform in a pattern area of 25 nm square or more. In other words, if the stress distribution is non-uniform, pattern distortion will occur due to the non-uniform stress distribution. Second, in order to form a fine pattern of 0.2 μm or less of the X-ray absorbing film, it must have a microcrystalline state or an amorphous structure. For example, if it has a columnar crystal structure, the fine pattern is formed, the edge shape of the pattern is roughened, and the pattern shape is deteriorated.

Conventionally, tantalum (Ta), tungsten (W), or compounds containing these metals have been used as the X-ray absorber film, and most of them are formed on the X-ray transparent film by the sputtering method. Has been formed. Then, as a material satisfying the above-mentioned characteristics, for example, a compound of tantalum and boron has been disclosed (Japanese Patent Laid-Open No. Hei 2 (1999))
-192116, hereinafter referred to as Conventional Example 1). According to this prior art example 1, the tantalum-boron compound is formed on the SiNX ray transmissive film by the RF magnetron sputtering method using Ar as a sputtering gas, and the low internal stress is a sputtering parameter which is a film forming parameter. It is obtained by controlling gas pressure and RF power. Such film stress is generally calculated from the difference in the amount of deformation of the silicon wafer before and after film formation.

However, the in-plane stress distribution has not been discussed so far because a reliable value cannot be obtained by measurement by deformation of a silicon wafer and there is no other suitable measurement method. .

[0007]

As described above, the compound of tantalum and boron (Ta-
B) has the following drawbacks. Smooth SiNX
Ar at the time of forming the stress of the Ta-B film formed on the line permeable film
The dependence due to gas pressure exhibits the characteristics as shown by the curve 51 in FIG. 2, and although a film with low stress can be obtained by controlling the gas pressure accurately, the rate of change of stress with respect to gas pressure is large. However, the stress changed due to minute pressure fluctuations, and it was not always possible to obtain a low stress film with good reproducibility. Further, with the further miniaturization of the pattern, smaller stress is required, so that more strict stress control is impossible with this method. In order to obtain a low stress film with good reproducibility, it is effective to reduce the rate of change of the stress and gas pressure, which is a film formation parameter (gradient in the figure).
Even if other film forming parameters such as F power are changed, there is almost no improvement.

As a verification experiment by the present inventors, the stress distribution within a 25 mm square was measured by the bulge method.
A uniform stress distribution of 70 MPa was confirmed within the plane. This non-uniform stress causes the plasma density to be non-uniform within the substrate surface because the Ar gas pressure is relatively high at about 1.5 Pa, which causes non-uniformity of film thickness and stress within the substrate surface. It turned out to be due to the fact.

Therefore, the technical problem of the present invention is to provide an X-ray mask having an X-ray absorbing film having an extremely small internal stress of the X-ray absorbing film, a uniform in-plane stress distribution, and excellent fine workability. It is to provide a manufacturing method of.

[0010]

In order to achieve the above technical object, in the method of manufacturing an X-ray mask of the present invention, the atomic number ratio (Ta / B) of the X-ray transparent film, tantalum and boron is 8%. A method of manufacturing an X-ray mask, comprising: an X-ray absorbing film contained within a range of 0.5 / 1.5 to 7.5 / 2.5, wherein an annealing treatment is performed after the X-ray absorbing film is formed. It is characterized by that.

The method of manufacturing an X-ray mask of the present invention uses X
Atom ratio of Ta and Boron (Ta /
In the method of manufacturing an X-ray mask for forming an X-ray absorption film containing B / B in a range of 8.5 / 1.5 to 7.5 / 2.5, the X-ray transmission film has a surface roughness of 0.2-20 nm
(Ra: center line average roughness).

Further, the method of manufacturing an X-ray mask according to the present invention comprises an X-ray transmitting film and an X-ray absorbing film, wherein the X-ray absorbing film contains tantalum and boron at an atomic ratio (Ta / B) of 8%. ．
A method for producing an X-ray mask having an X-ray absorption film containing 5 / 1.5 to 7.5 / 2.5, wherein a sputtering gas is used when the X-ray absorption film is formed by a sputtering method. Is characterized by using Xe.

In the present invention, silicon is preferably used as the substrate for forming the X-ray absorbing film, and silicon nitride and silicon carbide can be used as the X-ray transmitting film, but the substrate is not limited thereto. Not something.

[0014]

In the present invention, an X-ray absorption (Ta-B) film containing tantalum and boron in the atomic number ratio (Ta / B) in the range of 8.5 / 1.5 to 7.5 / 2.5. , It has an extremely small internal stress and can obtain a uniform stress distribution in the surface with good reproducibility. Therefore, the pattern position accuracy can be kept to 30 nm (3σ) or less, and further, it has an amorphous structure. An X-ray mask having a fine pattern of 0.2 μm or less can be obtained.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of the relationship between the annealing temperature and the internal stress in the X-ray mask manufacturing method of the present invention. FIG. 2 is a diagram showing an example of the relationship between argon (Ar) pressure and internal stress. FIG. 3 is a diagram showing another example of the relationship between gas pressure and internal stress.

In the method of manufacturing an X-ray mask of the present invention,
In the X-ray absorption (Ta-B) film containing tantalum and boron in the range where the atomic number ratio (Ta-B) is 8.5 / 1.5 to 7.5 / 2.5, sputtering After a Ta-B film having a compressive stress of about 100 MPa or less is formed by film formation, the film is annealed and the film stress changes to the tensile side. A low stress film is obtained by controlling the temperature. As shown in FIG. 1, according to this method, even if the stress varies during film formation, since the dependency (change degree) between the internal stress and the annealing temperature is small, any stress can be changed by changing the annealing temperature. It can be accurately controlled to low stress. Also, the stress distribution generated in the surface by this annealing is changed from 70 MPa to 50 MPa.
Can be improved to. Table 1 below shows the results of examining the effect of annealing.

[0018]

[Table 1]

Further, X-ray absorption (Ta-B) containing tantalum and boron in the atomic number ratio (Ta / B) of 8.5 / 1.5 to 7.5 / 2.5. In the membrane,
When the Ta-B film is formed by sputtering, by forming it on the X-ray transmissive film whose surface is rough in the range of 0.2 to 20 nm (Ra), the stress and gas as shown by the curve 12 in FIG. The rate of change in pressure can be reduced by an order of magnitude,
This makes it possible to obtain small stress with good reproducibility. Furthermore, the in-plane stress distribution can be made uniform up to 70 MPa. The Ta-B film also has an amorphous structure on the rough film.

Further, X-ray absorption (Ta-B) containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5 to 7.5 / 2.5. In the membrane,
X in the sputtering gas instead of Ar shown in the curve 52
By using e, the sputtering gas can be significantly reduced as shown by the curve 13 in FIG. 3, and the stress distribution becomes uniform up to 15 MPa with the uniformization of the plasma density.

Next, a specific example of manufacturing the X-ray mask of the present invention will be described.

(Embodiment 1) FIGS. 4A, 4B,
(C), (D) is sectional drawing which shows the manufacturing process of the X-ray mask which concerns on Example 1 of this invention in order. Referring to FIG. 4A, the X-ray transparent film 2 is formed on both surfaces of the silicon (Si) substrate 1a.
1 shows an X-ray mask membrane formed by depositing silicon nitride as a and 2b. The silicon substrate 1
Is 3 inches in diameter and 2 mm in thickness, and the crystal orientation (1
The silicon substrate of (00) was used. In addition, the X-ray transparent film 2a,
The silicon nitride as 2b is formed by a CVD method using dichlorosilane and ammonia to a thickness of 2 μm.

Next, as shown in FIG. 4B, an X-ray absorbing film 3a made of tantalum and boron is formed on the X-ray transmitting film 2a by RF magnetron sputtering to a thickness of 0.8 μm.
Formed to a thickness of. The sputter target is a sintered body containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5. Sputter gas is Ar, RF power is 300W, sputter pressure is 1.5Pa, and 80MP
A film having a compressive stress of a was obtained.

Next, this substrate was annealed in nitrogen at 250 ° C. for 1 hour to obtain X-ray having a low stress of 10 MPa or less.
A line absorber was obtained.

Next, an electron beam resistor was applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam. Using this resist pattern as a mask, reactive ion beam etching was performed, and as shown in FIG.
An X-ray absorption pattern 3 shown in (C) was formed (FIG. 4).
(C)).

Next, the X-ray transparent film 2b formed on the other side (back surface) of the substrate 1a is subjected to reactive ion etching using a mixed gas of a fluorine-based gas such as CF ₄ and an oxygen gas, and its center is formed. A 25 mm square area of the portion was removed by etching. Next, using the X-ray transmission films 2 and 2 remaining on the back surface as a mask, 10-50 wt% N heated to 80-100 ° C.
The silicon in the central portion was removed by immersing it in an aOH aqueous solution to form a mask support 10 having a 25 mm square self-supporting membrane, as shown in FIG. 4 (D).

The transfer accuracy of the X-ray mask material produced in Example 1 of the present invention was evaluated by a coordinate measuring machine.
It was confirmed that the accuracy was suppressed to the required accuracy of 0 nm (3σ) or less. Furthermore, since it has an amorphous structure, a fine pattern of 0.2 μm or less could be obtained.

Initial stress value due to sputtering film formation is 80MP
Not limited to a, as shown in Table 2, -130 to -20
The stress up to MPa can be controlled to 10 MPa or less by annealing up to 340 to 120 ° C. Here, the stress does not change at a temperature of 120 ° C. or lower, and the stress changes in the compression direction at a temperature of 340 ° C. or higher, so that control is difficult due to low stress.

The atmosphere of the annealing is not limited to N _2, and a reducing atmosphere such as Ar, in a vacuum, it is possible to similar stress control in the air. However, the optimum annealing temperature differs depending on the atmosphere.

(Embodiment 2) Next, an X-ray mask manufacturing method according to Embodiment 2 of the present invention will be described. The second embodiment of the present invention has the same process as the first embodiment,
It demonstrates using FIG. 4 (A), (B), (C), and (D).

Referring to FIG. 4A, silicon (Si)
An X-ray mask membrane was produced by depositing silicon carbide as the X-ray transparent film 2a on both surfaces of the substrate 1a. As the silicon substrate 1a, a silicon substrate having a size of 3 inches φ, a thickness of 2 mm and a crystal orientation (100) was used. The silicon carbide forming the X-ray transparent films 2a and 2b is formed to a thickness of 2 μm by the CVD method using dichlorosilane and acetylene. The surface of the X-ray transparent film 2a has a Ra (center line average roughness) of about 7 nm.

Next, as shown in FIG. 4B, an X-ray absorbing film 3a made of tantalum and boron is formed on the roughened X-ray transmitting film 2a by RF magnetron sputtering to a thickness of 0.8 μm. Formed. The sputter target contains tantalum and boron at an atomic ratio (Ta / B) of 8.5.
It is a sintered body containing at a ratio of /1.5. Sputter gas is A
At r, an RF power of 300 W and a sputtering pressure of 1.2 Pa were used to obtain a film having a low compressive stress of 10 MPa or less.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and this resist pattern is used as a mask for reactive ion beam etching. Giving, Figure 4 (C)
X-ray absorption pattern 3 was formed as shown in FIG.

Next, the X-ray transparent film 2b formed on the other side (back surface) of the substrate 1a is subjected to reactive ion etching using a mixed gas of a fluorine-based gas such as CF ₄ and an oxygen gas, and its central portion is formed. The 25 mm square area is removed by etching, and then the X-ray transparent film 2 remaining on the back surface is used as a mask.
The silicon in the central portion is removed by immersing in a 10-50 wt% NaOH aqueous solution heated to 80-100 ° C. to form a mask support 10 having a 25 mm square self-supporting membrane, as shown in FIG. 4 (D). did.

Here, the desirable range of the surface roughness of the permeable membrane is Ra 0.2 to 20 nm.

If the surface roughness is 0.2 nm or less, the stress controllability cannot be improved because it exhibits the same characteristics as the formation on the smooth SiN membrane shown by 51 in FIG. Further, when formed on the surface of 20 nm or more, a stress characteristic similar to that of 51 in FIG. 2 can be obtained and a low stress film can be manufactured, but the risk of the absorber surface increases and the pattern shape due to fine processing is impaired.

The transfer accuracy of the X-ray mask material produced in Example 2 of the present invention was evaluated by a coordinate measuring machine.
It was confirmed that the accuracy was suppressed to the required accuracy of 0 nm (3σ) or less. Furthermore, since it has an amorphous structure, a fine pattern of 0.2 μm or less could be obtained.

(Embodiment 3) Next, a method of manufacturing an X-ray mask according to Embodiment 3 of the present invention will be described. The manufacturing process of the third embodiment of the present invention is the same as that of the first and second embodiments described above.
Since it is similar to the above, it will be described with reference to FIG. FIG. 4 (A)
Referring to, a silicon nitride film was formed as the X-ray transparent film 2a on both surfaces of the silicon (Si) substrate 1a to form an X-ray mask membrane. As the silicon substrate 1a, a silicon substrate having a size of 3 inches φ, a thickness of 2 mm and a crystal orientation (100) was used. Further, silicon carbide as an X-ray transparent film is formed by CVD using dichlorosilane and ammonia to a thickness of 2 μm.

Next, an X-ray absorbing film 3a made of tantalum and boron was formed on the X-ray transmitting film 2 by RF magnetron sputtering to a thickness of 0.8 μm (FIG. 4).
(B)). The sputter target is a sintered body containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5. Sputtering gas is Xe and Rf power is 300
A film having a low compressive stress of 10 MPa or less was obtained with W and a sputtering pressure of 0.38 Pa.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and the resist pattern is used as a mask for reactive ion beam etching. Giving, Figure 4 (C)
X-ray absorption pattern 3 shown in FIG.

Next, the X-ray transparent film 2b formed on the other side (rear surface) of the substrate 1a is subjected to reactive ion etching using a mixed gas of a fluorine-based gas such as CF ₄ and an oxygen gas, and its central portion is formed. The 25 mm square area of is removed by etching, and then the X-ray transmissive film remaining on the back surface is used as a mask.
The center silicon is removed by immersing it in a 10-50 wt% NaOH aqueous solution heated to 0-100 ° C.
A mask support 10 having a 25 mm square free-standing membrane was formed (FIG. 4D).

When the transfer accuracy of the X-ray mask manufactured in Example 3 of the present invention was evaluated by a coordinate measuring machine, it was 20n.
It was confirmed that the accuracy was suppressed below the required accuracy of m (3σ). Furthermore, since it has an amorphous structure, a fine pattern of 0.2 μm or less could be obtained.

(Embodiment 4) Next, a method of manufacturing an X-ray mask according to Embodiment 4 will be described. Since Example 4 of the present invention includes the steps of Examples 1 and 2, FIG.
This will be described with reference to (B), (C) and (D).

Silicon carbide was deposited as the X-ray transparent film 2 on both surfaces of the silicon (Si) substrate 1a to prepare an X-ray mask membrane. As the silicon substrate 1a, a silicon substrate having a size of 3 ″ φ and a thickness of 2 mm and a crystal orientation (100) was used. Further, silicon carbide as an X-ray transparent film was formed by a CVD method using dichlorosilane and acetylene. 2μ
The film is formed to a thickness of m. The surface of this transmission film is roughened to Ra (center line average roughness) of about 7 nm.

Next, an X-ray absorption film 3a made of tantalum and boron was formed on the X-ray transmission film 2 having a rough surface by RF magnetron sputtering to a thickness of 0.8 μm). The sputter target is a sintered body containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5. Sputter gas is Ar, Rf power is 300W,
A film having a compressive stress of 130 MPa was obtained with a sputtering pressure of 0.8 Pa.

Next, this substrate was annealed in nitrogen at 340 ° C. for 1 hour to obtain a film having a low stress of 10 MPa or less.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and this resist pattern is used as a mask for reactive ion beam etching. Then, the X-ray absorption pattern 3 was formed.

Next, the central portion of the X-ray transparent film 21a formed on the other side (back surface) of the substrate 1a by reactive ion etching using a mixed gas of a fluorine-based gas and oxygen gas such as CF ₄ The 25 mm square area of is removed by etching, and then the X-ray transparent film remaining on the back surface is used as a mask.
The silicon in the central portion was removed by immersing in a 10-50 wt% NaOH aqueous solution heated to 80-100 ° C. to form a mask support 1 having a 25 mm square free-standing membrane.

When the transfer accuracy of the X-ray mask material produced in this example was evaluated by a coordinate measuring machine, it was 20 nm.
It was confirmed that the accuracy was suppressed below the required accuracy of (3σ). Furthermore, since it has an amorphous structure,
A fine pattern of 2 μm or less could be obtained.

(Embodiment 5) Next, an X-ray mask manufacturing method according to Embodiment 5 will be described. Example 4 of the present invention
Since the steps of Examples 1 and 3 are included in FIG.
This will be described with reference to (B), (C) and (D).

An X-ray mask membrane was prepared by depositing silicon nitride having a smooth surface as the X-ray transparent film 2 on both surfaces of the silicon (Si) substrate 1a. The silicon substrate 1a has a size of 3 ″ φ, a thickness of 2 mm, and a crystal orientation (100).
The silicon substrate of was used. Moreover, silicon carbide as an X-ray transparent film is formed by CVD using dichlorosilane and ammonia.
It is formed into a film having a thickness of 2 μm by the method.

Next, an X-ray absorbing film 3a made of tantalum and boron was formed on the X-ray transmitting film 2 by RF magnetron sputtering to a thickness of 0.8 μm). The sputter target consists of tantalum and boron in the atomic ratio (Ta /
It is a sintered body containing B) in a ratio of 8.5 / 1.5. The sputtering gas was Xe, the Rf power was 300 W, the sputtering pressure was 0.34 Pa, and a film having a compressive stress of 80 MPa was obtained.

Next, this substrate was annealed in nitrogen at 200 ° C. for 1 hour to obtain a low stress film of 10 MPa or less.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and this resist pattern is used as a mask for reactive ion beam etching. Then, the X-ray absorption pattern 3 was formed.

Next, the central portion of the X-ray transparent film 21a formed on the other side (back surface) of the substrate 1a by reactive ion etching using a mixed gas of a fluorine-based gas and oxygen gas such as CF ₄ The 25 mm square area of is removed by etching, and then the X-ray transparent film remaining on the back surface is used as a mask.
The silicon in the central portion was removed by immersing in a 10-50 wt% NaOH aqueous solution heated to 80-100 ° C. to form a mask support 1 having a 25 mm square free-standing membrane.

When the transfer accuracy of the X-ray mask material manufactured in this example is evaluated by a coordinate measuring machine, it is 15 nm.
It was confirmed that the accuracy was suppressed below the required accuracy of (3σ). Furthermore, since it has an amorphous structure,
A fine pattern of 2 μm or less could be obtained.

(Sixth Embodiment) Next, a method of manufacturing an X-ray mask according to a sixth embodiment will be described. Example 4 of the present invention
Since the steps of Examples 2 and 3 are included in FIG.
This will be described with reference to (B), (C) and (D).

An X-ray mask membrane was prepared by depositing silicon carbide as the X-ray transparent film 2 on both sides of the silicon (Si) substrate 1a. As the silicon substrate 1a, a silicon substrate having a size of 3 ″ φ and a thickness of 2 mm and a crystal orientation (100) was used. Further, silicon carbide as an X-ray transparent film was formed by a CVD method using dichlorosilane and acetylene. 2μ
The film is formed to a thickness of m. The surface of this transmission film is roughened to Ra (center line average roughness) of about 7 nm.

Next, an X-ray absorption film 3a made of tantalum and boron was formed on the X-ray transmission film 2 having a rough surface by RF magnetron sputtering to a thickness of 0.8 μm). The sputter target is a sintered body containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5. Sputter gas is Xe, Rf power is 300W,
A film with a low stress of 10 MPa or less was obtained with a sputtering pressure of 0.15 Pa.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and this resist pattern is used as a mask for reactive ion beam etching. Then, the X-ray absorption pattern 3 was formed.

Next, the X-ray transparent film 21a formed on the other side (rear surface) of the substrate 1a is subjected to reactive ion etching using a mixed gas of a fluorine-based gas such as CF ₄ and an oxygen gas, and its central portion is formed. The 25 mm square area of is removed by etching, and then the X-ray transparent film remaining on the back surface is used as a mask.
The silicon in the central portion was removed by immersing in a 10-50 wt% NaOH aqueous solution heated to 80-100 ° C. to form a mask support 1 having a 25 mm square free-standing membrane.

When the transfer accuracy of the X-ray mask material manufactured in this example was evaluated by a coordinate measuring machine, it was 15 nm.
It was confirmed that the accuracy was suppressed below the required accuracy of (3σ). Furthermore, since it has an amorphous structure,
A fine pattern of 2 μm or less could be obtained.

(Embodiment 7) Next, a method of manufacturing an X-ray mask according to Embodiment 7 will be described. Example 4 of the present invention
Since the steps of Examples 1, 2, and 3 are included in FIG.
This will be described with reference to (A), (B), (C) and (D).

Silicon carbide was deposited as an X-ray transparent film 2 on both surfaces of the silicon (Si) substrate 1a to prepare an X-ray mask membrane. As the silicon substrate 1a, a silicon substrate having a size of 3 ″ φ and a thickness of 2 mm and a crystal orientation (100) was used. Further, silicon carbide as an X-ray transparent film was formed by a CVD method using dichlorosilane and acetylene. 2μ
The film is formed to a thickness of m. The surface of this transmission film is roughened to Ra (center line average roughness) of about 7 nm.

Next, an X-ray absorption film 3a made of tantalum and boron was formed on the X-ray transmission film 2 having a rough surface by RF magnetron sputtering to a thickness of 0.8 μm). The sputter target is a sintered body containing tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5. Sputter gas is Xe, Rf power is 300W,
A film having a compressive stress of 130 MPa was obtained with a sputtering pressure of 0.10 Pa.

Next, this substrate was annealed in nitrogen at 340 ° C. for 1 hour to obtain a low stress film of 10 MPa or less.

Next, an electron beam resist is applied on the X-ray absorbing film 3a to form a resist pattern having a line width of 0.2 μm or less by an electron beam, and the resist pattern is used as a mask for reactive ion beam etching. Then, the X-ray absorption pattern 3 was formed.

Next, the central portion of the X-ray transparent film 21a formed on the other side (back surface) of the substrate 1a by reactive ion etching using a mixed gas of a fluorine-based gas and oxygen gas such as CF ₄ The 25 mm square area of is removed by etching, and then the X-ray transparent film remaining on the back surface is used as a mask.
The silicon in the central portion was removed by immersing in a 10-50 wt% NaOH aqueous solution heated to 80-100 ° C. to form a mask support 1 having a 25 mm square free-standing membrane.

When the transfer accuracy of the X-ray mask material manufactured in this example is evaluated by a coordinate measuring machine, it is 15 nm.
It was confirmed that the accuracy was suppressed below the required accuracy of (3σ). Furthermore, since it has an amorphous structure,
A fine pattern of 2 μm or less could be obtained.

Table 2 below shows the results of summarizing the stress distribution and the positional accuracy in each of the examples described above.

[0071]

[Table 2]

As a comparative example, when the positional accuracy and the in-plane stress distribution of the Ta-B film having a stress of 10 MPa or less were examined by the conventional example 1, the results were 50 nm and 80 MPa, respectively. The superiority of was proved.

In the embodiment of the present invention, etching of silicon with NaOH was carried out as a method for making the X-ray transparent film self-supporting. However, the etching method is not limited to this method, and hydrofluoric nitric acid (HF and HNO ₃ A mixed solution) or the like can also be used.

In the first to third embodiments, the silicon substrate has a plane orientation (100) and a size of 3 inches φ and a thickness of 2 mm, but the present invention is not limited to this.
The plane orientation may be (111), etc., and the generally preferred size is 3
The thickness of inch φ and 4 inch φ is 0.38 to 2 mm. Further, the present invention is not limited to the size and thickness of the glass supporting frame. Furthermore, although silicon carbide and silicon nitride are used as the X-ray transparent film in the first to third embodiments of the present invention, silicon, diamond, etc. can also be used.

The surface roughness of the X-ray transparent film can be controlled not only by the material, the film forming method and the film forming conditions but also by etching the surface and forming other materials such as ITO.

In the embodiment of the present invention, the X-ray absorbing film is X-ray.
Although it is formed on the X-ray transmission film, the same effect can be obtained by forming it on the substrate on which another film such as an antireflection film or an etching stopper is formed on the X-ray transmission film. Further, the annealing atmosphere is not limited to nitrogen, but may be an inert gas such as Ar, air, or vacuum. Further, the annealing time is not limited to 1 hour, and a practical range of 5 minutes or more and 2 hours or less is desirable.

[0077]

As described above, according to the present invention, the atomic number ratio (Ta-B) of tantalum and boron is 8.5 / 1.5 to 7.5 / 2.5. In the X-ray absorption (Ta-B) film contained in the range, annealing is performed after the X-ray absorption film is formed, and the film is formed on the rough X-ray transmission film.
Alternatively, by using Xe as the sputtering gas, an in-plane uniform absorber film with low stress can be produced with good reproducibility, and a method for producing an X-ray mask that suppresses pattern distortion precisely can be provided.

Further, according to the present invention, since the X-ray absorption film has an amorphous structure, it is possible to provide an X-ray mask manufacturing method capable of obtaining an X-ray mask having a fine pattern of 0.2 μm or less. You can

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between annealing temperature and internal stress in an X-ray mask manufacturing method according to an example of the present invention.

FIG. 2 is a diagram showing a relationship between Ar pressure and internal stress in an X-ray mask manufacturing method according to an example of the present invention.

FIG. 3 is a diagram showing the relationship between gas pressure and internal stress in the method of manufacturing an X-ray mask according to an example of the present invention.

FIG. 4 is a diagram sequentially showing each step of the method for manufacturing the X-ray mask according to the embodiment of the present invention.

[Explanation of symbols]

 1a Silicon substrate 1 Mask substrate 2a, 2b X-ray transparent film 2 X-ray transparent film mask 3a X-ray absorbing film 3 X-ray absorbing pattern 10 Mask support

Claims (3)

[Claims] 1. An atomic number ratio (Ta / B) of an X-ray transparent film to tantalum and boron is 8.5 / 1.5 to 7.5 / 2.5.
A method of manufacturing an X-ray mask, comprising: an X-ray absorbing film contained in the range of: wherein an annealing treatment is performed after the X-ray absorbing film is formed. 2. Tantalum and boron in an atomic ratio (Ta / B) of 8.5 / 1.5 to 7.5 / 2.
In the method of manufacturing an X-ray mask for forming an X-ray absorption film containing 5 to 5, the X-ray transmission film has a surface roughness of 0.2-20 nm (Ra: center line average roughness). A method for manufacturing an X-ray mask, comprising: 3. An X-ray transmission film and an X-ray absorption film, wherein the X-ray absorption film contains tantalum and boron in an atomic ratio (Ta / Ta).
B) a method for producing an X-ray mask having an X-ray absorbing film containing 8.5 / 1.5 to 7.5 / 2.5, wherein the X-ray absorbing film is formed by a sputtering method. A method of manufacturing an X-ray mask, characterized in that Xe is used as a sputtering gas when performing.