JP2790656B2 - X-ray mask material and X-ray mask - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray mask material and an X-ray mask used for X-ray lithography.

[Prior Art] In the field of the semiconductor industry, a lithography technique is used as a technique for forming an integrated circuit having a fine pattern on a silicon substrate or the like. This lithography technique is generally performed as follows.

Irradiating the exposure electromagnetic wave to a mask having a pattern corresponding to a fine pattern such as an integrated circuit made of a metal or the like having an operation of absorbing the exposure electromagnetic wave on a substrate having an operation of transmitting the exposure electromagnetic wave; As a result, the fine pattern of the mask is transferred to the resist applied on the silicon substrate or the like. Next, based on this resist pattern, various processes such as etching, impurity implantation, and dielectric film fabrication are performed to form an integrated circuit or the like having a fine pattern on a silicon substrate or the like.

Conventionally, a photolithography method for transferring a fine pattern using visible light and ultraviolet light as an exposure electromagnetic wave has been used. However, recently, there has been a demand for a technology for transferring a finer pattern, which exceeds the physical limit of visible light and ultraviolet light, and in order to transfer such a fine pattern, an X-ray having a shorter wavelength has been required. An X-ray lithography method in which is used as an exposure electromagnetic wave has been attempted.

By the way, X used in this X-ray lithography method
The line mask material includes a substrate, a film having a large X-ray transmittance formed on the substrate (hereinafter, referred to as an X-ray transmission film), and a film having a large X-ray absorption formed on the X-ray transmission film. (Hereinafter, X
(Referred to as a line absorbing film). Where generally X
The X-ray transmission film is an extremely thin film composed of atoms having a small atomic number, and the X-ray absorption film is an extremely thin film composed of a metal having a high X-ray absorption.

Needless to say, a material having a high X-ray absorption rate must be used for the X-ray absorption film, but the following requirements must be satisfied. First, the internal stress is small. This is because, as described above, since the X-ray absorbing film is formed on an extremely thin X-ray transmitting film, if the internal stress of the X-ray absorbing film is large, the internal stress causes distortion in the X-ray mask. This is because the pattern transfer accuracy cannot be ensured. Second, the film structure is suitable for forming a fine pattern. In many cases, the required pattern size is 0.25 μm or less, and therefore, the film structure must be in an amorphous state or a microcrystalline state in which a pattern of 0.25 μm or less can be formed.

Conventionally, the X-ray mask material used as the X-ray absorbing film is composed of gold (Au), tantalum (Ta), tungsten (W), rhenium (Re), or a metal and a nonmetallic element. Compounds, such as tantalum nitride,
Tungsten nitride, tantalum oxide, tungsten nitride and the like were used.

[Problems to be Solved by the Invention] However, each of the above-mentioned conventional X-ray absorbing films has the following disadvantages.

First, Au is soft, malleable and ductile,
There is a disadvantage that the pattern size cannot be changed with time. In addition, Au is chemically inert, and is extremely difficult to process by wet etching and dry etching, so that there is a disadvantage that a fine pattern cannot be directly formed. Therefore, in order to form a fine pattern on the Au film, a stencil pattern is formed in advance on a resist or the like, and Au is deposited in the stencil pattern using an electrolytic plating method to form a fine pattern of Au. The way had been done. However, the electrolytic plating method is the most important for producing an X-ray absorbing film. There was a drawback that precise internal stress controllability was not obtained, and that the film was easily contaminated because of the solution reaction.

Next, for metals other than Au, for example, Ta, W, and Re, the sputtering method is almost the only method for forming these films. There was. When producing an X-ray absorption film by a sputtering method, it has been extremely difficult to precisely control the internal stress. It is clear that the internal stress of the film depends on the sputter gas pressure, but this dependency is such that the change in the internal stress changes sharply with a small change in the gas pressure. Therefore, the range of gas pressure for obtaining a desired small internal stress is limited to an extremely small range. In addition, the sputter gas pressure was the only parameter that could control the internal stress. Further, a film having a small internal stress can be obtained only under a condition of a large sputter gas pressure, and the film obtained under these conditions has a low density and contains impurities, so that the X-ray absorption rate decreases and the grain size decreases. There is a drawback that microfabrication is impossible because of its extremely large size.

Next, a compound composed of a metal and a non-metal element, specifically, a film of tantalum nitride, tungsten nitride, tantalum oxide, tungsten oxide, or the like is obtained by the same sputtering method as in the case of forming the single metal film. In this case, while these films are in an amorphous state or in a microcrystalline state, it is easy to obtain excellent film structures in performing fine processing, while maintaining these excellent film structures, In addition, a film having a small internal stress cannot be easily obtained. In other words, when trying to obtain a film with a small internal stress, micro-machining is impossible due to a change from an amorphous state to a crystalline state due to phase transition, or from a micro-crystalline state to a crystalline state with a larger crystal grain size. There was a disadvantage. Further, with respect to the disadvantages of controlling the internal stress and the X-ray absorptivity, they have almost the same disadvantages as in the case of the above-mentioned single metal, and were extremely insufficient as an X-ray absorbing film.

Accordingly, a first object of the present invention is to eliminate the above-mentioned disadvantages,
An object of the present invention is to provide an X-ray mask material having an X-ray absorbing film having a film structure with small internal stress.

A second object of the present invention is to provide an X-ray mask having an extremely fine pattern using the X-ray mask material obtained by achieving the first object.

[Means for Solving the Problems] A first object of the present invention is to provide an X-ray permeable film and
In an X-ray mask material provided with a X-ray absorbing film in order,
This is achieved by an X-ray mask material characterized in that the radiation absorbing film comprises tantalum, silicon and boron.

A second object of the present invention is to provide an X-ray mask
This is achieved by an X-ray mask characterized in that the X-ray mask is obtained by finely patterning a line absorbing film.

 Hereinafter, the present invention will be described in detail.

The X-ray mask material of the present invention is obtained by sequentially providing an X-ray transmission film and an X-ray absorption film on a substrate. Here, a commonly used substrate such as a silicon substrate is used as the substrate, and a commonly used X-ray permeable film such as silicon nitride, boron nitride, or silicon carbide is used as the X-ray permeable film. Can be

In the X-ray mask material of the present invention, the X-ray absorbing film has a novel structure, and is characterized by containing tantalum, silicon, and boron.

The reason why the film containing tantalum, silicon and boron is selected as the X-ray absorbing film in the X-ray mask material of the present invention is as follows.

The first reason is that an X-ray absorbing film containing tantalum, silicon and boron can be easily formed on a substrate at a low temperature by a sputtering method. Therefore, thermal CVD
The mask distortion due to heat does not occur unlike the method. Further, the sputtering method can form a film more easily than the electrolytic plating method and the CVD method, and has a higher deposition rate.

The second reason is that the X-ray absorption film containing tantalum, silicon and boron has a small internal stress even when formed by a sputtering method in which the sputtering gas pressure is reduced.
In addition, if the film is formed at a low gas pressure, the advantages of high purity, containing no impurities, and high X-ray absorptivity can be obtained. Therefore, the film has a small internal stress, and has a high density and contains no impurities. In addition, a film having a large X-ray absorptivity can be obtained. Regarding this internal stress, the present inventor, for example, 2.
It has been confirmed that the internal stress can be easily controlled by changing the power applied to the sputter target under conditions of a small gas pressure such as 5 Pa or less. In this case, since the control of the input power is different from the control of the sputtering gas pressure, extremely precise control is possible,
By setting the input power accurately, the internal stress of the obtained film can be made almost completely zero. Since the film is formed under a further lower gas pressure condition, a film having a high density and extremely few impurities can be obtained, and therefore, an X-ray absorption film having a sufficient X-ray absorption rate can be obtained.

In the formation of a film containing tantalum, silicon, and boron by a sputtering method, a target material containing tantalum, silicon, and boron may be used as a target material,
Using pure tantalum, silane (Si
Gas containing silicon atoms such as H ₂ ) and diborane (B
A reactive sputtering method of mixing a gas containing a boron atom such as ₂ H ₆ ) may be used.

The composition of the X-ray absorbing film containing tantalum, silicon, and boron is represented by the general formula: Ta _x Si _{(1-x) y} B _{(1-x) (1-y)} (0.75 ≦ x ≦ 0.85, 0 <y <1) is preferred. The reason is as follows.

The first reason is that when the total amount of tantalum, silicon and boron is 1.0, the atomic ratio x of tantalum exceeds 0.85, and when the amount of tantalum increases and the amount of silicon and boron decreases, the atomic ratio of silicon and boron decreases. Whatever value is taken, the crystalline state of the formed film becomes microcrystalline, and its particle size becomes, for example, a size exceeding 15 nm, and the atomic ratio x of tantalum becomes less than 0.75, and tantalum decreases, Even if silicon and boron are increased, the crystal state of the formed film becomes microcrystalline and the particle size becomes larger than, for example, 15 nm, regardless of the value of the atomic ratio of silicon and boron. In the case of, the crystal grains of the film are large, so that the upper surface and the wall surface of the formed pattern are not smooth, whereas the atomic ratio x of tantalum is 0.75 to 0.85, Even the atomic ratio of silicon and boron will take any value, because film is a small crystallites state of or grains in an amorphous state, the upper surface and the wall surface of the pattern to be formed is because the smoothing.

In the present invention, although the X-ray absorption film contains silicon and boron, it contains a majority of tantalum, so the chemical properties in dry etching are almost the same as those of the tantalum single film. The conventional processing technology used can be used as it is.

According to the present invention, an X-ray mask having a fine pattern of, for example, 0.25 μm or less can be obtained by using an X-ray mask material having the above characteristics and finely patterning the X-ray absorbing film by a conventional method. .

[Examples] Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited to these Examples.

Example 1 An example in which the atomic ratio x of tantalum constituting the X-ray absorption film is 0.85 will be described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a fired body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.85 / 0.075 / 0.075. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. The sputtering conditions were an rf power of 400 W (8.64 W / cm ² ) and a sputtering gas pressure of 1.63 Pa. The deposition initiation temperature was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to spectroscopy for Chemical Analysis), it was confirmed that the composition ratio was the same as that of the target, and this composition ratio was almost constant in the depth direction of the film, and that no impurities were contained.

This X-ray absorbing film is in a microcrystalline state (crystal grain size 10n).
m) and the stress is the measurement limit (1 × 10 ⁸ dyn / cm ² )
It was the following. Further, the obtained film was extremely hard and hard to be damaged. Furthermore, when the density of the obtained film was determined by a gravimetric method, it was 16.1 g / cm ³ , and it was confirmed that the film had a sufficient density as an X-ray absorbing film.

Next, after the surface of the X-ray absorbing film was cleaned, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to an X-ray absorbing film by reactive ion beam etching. At this time, a pattern having a line width of 0.25 μm could be formed on the X-ray absorbing film. In addition, the reactive ion beam etching method was performed under the conditions of an ion acceleration energy of 400 V and an etching temperature of 15 ° C. using chlorine and carbon tetrafluoride as an etching gas at a flow rate of 50 cc per minute, respectively. In the case of using tantalum, the etching rate was almost the same as in the case of the tantalum single film, and it was confirmed that a practically sufficient etching rate was obtained.

Finally, the center of the Si substrate was etched away by immersion in a saturated sodium hydroxide aqueous solution maintained at 90 ° C.
A line mask was prepared. Furthermore, when the synchrotron radiation was exposed to a 0.6 μm-thick PMMA resist through a mask pattern, it had sufficient contrast and line width.
A resist pattern of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorbing film in the present invention was confirmed.

Example 2 An example in which the atomic ratio x of tantalum constituting the X-ray absorption film is 0.80 will be described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.80 / 0.15 / 0.05. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. Sputtering conditions are rf power
The pressure was 400 W (8.64 W / cm ² ) and the sputtering gas pressure was 1.87 Pa. The deposition initiation temperature was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to spectroscopy for Chemical Analysis), it was confirmed that the composition ratio was the same as that of the target, and this composition ratio was almost constant in the depth direction of the film, and that no impurities were contained.

This X-ray absorbing film was in an amorphous state, and its stress was below the measurement limit (1 × 10 ⁸ dyn / cm ² ). Further, the obtained film was extremely hard and hard to be damaged. Further, when the density of the obtained film was determined by a gravimetric method, it was 15.9 g / cm ³ , and it was confirmed that the film had a sufficient density as an X-ray absorbing film.

Next, after the surface of the X-ray absorbing film was cleaned, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to the X-ray absorbing film by reactive ion beam etching. At this time, a pattern having a line width of 0.25 μm could be formed on the X-ray absorbing film. Note that the reactive ion beam etching method was performed under the conditions of an ion acceleration energy of 400 V and an etching temperature of 15 ° C. using chlorine and carbon tetrafluoride as an etching gas at a flow rate of 50 cc per minute, respectively. Also when using, the etching rate is almost the same as the case of the tantalum single film,
It was confirmed that an etching rate sufficient for practical use was obtained.

Finally, the center of the Si substrate was etched away by immersion in a saturated sodium hydroxide aqueous solution maintained at 90 ° C.
A line mask was prepared. Furthermore, when the synchrotron radiation was exposed to a 0.6 μm-thick PMMA resist through a mask pattern, it had sufficient contrast and line width.
A resist pattern of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorption film in the present invention was confirmed.

Example 3 An example in which the atomic ratio x of tantalum constituting the X-ray absorption film is 0.80 (however, the ratio of silicon to boron is different from that of Example 2) is described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.80 / 0.1 / 0.1. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. The sputtering condition is rf power 40
The power was 0 W (8.64 W / cm ² ) and the sputtering gas pressure was 1.88 Pa.
The temperature at the start of the deposition was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to spectroscopy for chemical analysis), it was confirmed that the composition ratio was the same as that of the target, that the composition ratio was almost constant in the depth direction of the film, and that no impurities were contained.

This X-ray absorbing film was in an amorphous state, and the stress was below the measurement limit (1 × 10 ⁸ dyn / cm ² ). Further, the obtained film was extremely hard and hard to be damaged. Further, when the density of the obtained film was determined by a gravimetric method, it was 15.8 g / cm ³ , and it was confirmed that the film had a sufficient density as an X-ray absorbing film.

Next, after the surface of the X-ray absorbing film was cleaned, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to the etching absorption film by reactive ion beam etching. At this time, a pattern having a line width of 0.25 μm is defined as X
It could be formed on a line absorbing film. Note that the reactive ion beam etching method was performed under the conditions of an ion acceleration energy of 400 V and an etching temperature of 15 ° C. using chlorine and carbon tetrafluoride as an etching gas at a flow rate of 50 cc per minute, respectively. In the case of using tantalum, the etching rate was almost the same as in the case of the tantalum single film, and it was confirmed that a practically sufficient etching rate was obtained.

Finally, the center of the Si substrate was etched away by immersion in a saturated sodium hydroxide aqueous solution maintained at 90 ° C.
A line mask was prepared. Furthermore, when the synchrotron radiation was exposed to a 0.6 μm-thick PMMA resist through a mask pattern, it had sufficient contrast and line width.
A pattern of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorbing film of the present invention was confirmed.

Example 4 An example in which the atomic ratio x of tantalum constituting the X-ray absorption film is 0.80 (however, the ratio of silicon to boron is different from Examples 2 and 3) is described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.80 / 0.05 / 0.15. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. Sputtering conditions are rf power
The pressure was 400 W (8.64 W / cm ² ) and the sputtering gas pressure was 1.89 Pa. The temperature at the start of the deposition was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to spectroscopy for Chemical Analysis), it was confirmed that the composition ratio was the same as that of the target, and this composition ratio was almost constant in the depth direction of the film, and that no impurities were contained.

This X-ray absorbing film was in an amorphous state, and its stress was below the measurement limit (1 × 10 ⁸ dyn / cm ² ). Further, the obtained film was extremely hard and hard to be damaged. Further, when the density of the obtained film was determined by a gravimetric method, it was 15.6 g / cm ³ , and it was confirmed that the film had a sufficient density as an X-ray absorbing film.

Next, after the surface of the X-ray absorbing film was cleaned, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to an X-ray absorbing film by reactive ion beam etching. At this time, a pattern having a line width of 0.25 μm could be formed on the X-ray absorbing film. Note that the reactive ion beam etching method was performed under the conditions of an ion acceleration energy of 400 V and an etching temperature of 15 ° C. using chlorine and carbon tetrafluoride as an etching gas at a flow rate of 50 cc per minute, respectively. In the case of using tantalum, the etching rate was almost the same as in the case of the tantalum single film, and it was confirmed that a practically sufficient etching rate was obtained.

Finally, the center of the Si substrate was etched away by immersion in a saturated sodium hydroxide aqueous solution maintained at 90 ° C.
A line mask was prepared. Furthermore, when the synchrotron radiation was exposed to a 0.6 μm-thick PMMA resist through a mask pattern, it had sufficient contrast and line width.
A pattern of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorbing film of the present invention was confirmed.

Example 5 An example in which the atomic ratio x of tantalum constituting the X-ray absorption film is 0.75 will be described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron in an atomic ratio (Ta / Si / B) of 0.75 / 0.125 / 0.125. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. The sputtering conditions were an rf power of 400 W (8.64 W / cm ² ) and a sputtering gas pressure of 2.13 Pa. The temperature at the start of the deposition was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to spectroscopy for Chemical Analysis), it was confirmed that the composition was the same as that of the target, and this composition was almost constant at the depth of the film, and that no impurities were contained.

This X-ray absorbing film is in a microcrystalline state (crystal grain size 10n).
m) and the stress is the measurement limit (1 × 10 ⁸ dyn / cm ² )
It was the following. Further, the obtained film was extremely hard and hard to be damaged. Furthermore, when the density of the obtained film was determined by a gravimetric method, it was 15.3 g / cm ³ , and it was confirmed that the film had a sufficient density as an X-ray absorbing film.

Next, after the surface of the X-ray absorbing film was cleaned, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to an X-ray absorbing film by reactive ion beam etching. At this time, a pattern having a line width of 0.25 μm could be formed on the X-ray absorbing film. Note that the reactive ion beam etching method was performed under the conditions of an ion acceleration energy of 400 V and an etching temperature of 15 ° C. using chlorine and carbon tetrafluoride as an etching gas at a flow rate of 50 cc per minute, respectively. In the case of using tantalum, the etching rate was almost the same as in the case of the tantalum single film, and it was confirmed that a practically sufficient etching rate was obtained.

Finally, the center of the Si substrate was etched away by immersion in a saturated sodium hydroxide aqueous solution maintained at 90 ° C.
A line mask was prepared. Furthermore, when synchrotron radiation was exposed to a 0.6 μm thick PMMA register through a mask pattern, it had sufficient contrast and line width.
A pattern of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorbing film of the present invention was confirmed.

Examples 6 to 19 In the same manner as in Example 1 except that the atomic ratio (Ta / Si / B) of tantalum, silicon and boron constituting the sputter target was varied, a total of 14 Type X
A line absorbing film was prepared.

When the film structure, the magnitude of the internal stress, the density, and the like of each of the X-ray absorbing films thus manufactured were measured in the same manner as in Example 1, any of the X-ray absorbing films was preferable as the X-ray absorbing film. Was confirmed.

Further, in any of the X-ray absorbing films, in the same manner as in Example 1.
It was confirmed that a pattern having a line width of 0.25 μm could be formed, and a practically sufficient etching rate was obtained.

Further, a total of 14 types of X-ray masks were produced in the same manner as in Example 1, and the fine pattern was transferred to the resist in the same manner as in Example 1. When any of the X-ray masks was used, sufficient contrast was obtained. And a pattern having a line width of 0.25 μm could be transferred. Thereby, the effectiveness of the X-ray absorbing film of the present invention was confirmed.

Comparative Example 1 A comparative example in which the X-ray absorbing film is formed only by tantalum is shown below.

An X-ray absorbing film made of tantalum is applied to a 2 μm thick silicon nitride film (X-ray transmitting film) formed on a Si (100) substrate by rf (high frequency) magnetron sputtering.
An X-ray mask material was obtained having a thickness of 6 μm.

The sputter target is a sintered body containing only tantalum. The sputtering gas is argon, and the argon flow rate is every minute
It was 27.0cc. Sputtering conditions were rf power 290W (6.36
W / cm ² ) and the sputtering gas pressure was 3.0 Pa. The temperature at the start of the deposition was room temperature.

The X-ray absorbing film prepared under the above conditions has ESCA (Electr
on Spectoroscopy for Chemical Analysis)
It was confirmed that impurities such as oxygen, nitrogen, and carbon in an atomic ratio of about 20% were contained.

This X-ray absorbing film has a columnar crystal state (columnar crystal having a diameter of 20 mm).
nm) and the stress is the measurement limit (1 × 10 ⁸ dyn / cm ² )
It was the following.

Next, after cleaning the surface of the X-ray absorbing film, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to the X-ray absorbing film by reactive ion beam etching. At this time, the upper surface and the wall surface of the formed pattern were not smooth, and a pattern having a desired line width of 0.25 μm could not be formed.

Example 20 An example in which the atomic ratio x of tantalum constituting the X-ray absorbing film is 0.90 is described below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.90 / 0.05 / 0.05. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. Sputtering conditions are rf power
The power was 400 W (8.64 W / cm ² ) and the sputtering gas pressure was 1.38 Pa. The temperature at the start of the deposition was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to pectoroscopy for Chemical Analysis), it was confirmed that the composition ratio was the same as that of the target, and this composition ratio was almost constant in the depth direction of the film, and that no impurities were contained.

This X-ray absorbing film is in a microcrystalline state (crystal grain size 20n).
m) and the stress is the measurement limit (1 × 10 ⁸ dyn / cm ² )
It was the following.

Next, after cleaning the surface of the X-ray absorbing film, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to an X-ray absorbing film by reactive ion beam etching to form a pattern having a line width of 0.25 μm. The upper surface and the wall surface of the pattern formed at this time were slightly inferior to those of Examples 1 to 19 having smoothness.

Example 21 A comparative example in which the atomic ratio x of tantalum constituting the X-ray absorbing film is 0.70, which is not included in the limited range of the present invention, is shown below.

An X-ray absorbing film made of tantalum, silicon and boron is applied to a silicon nitride film (X-ray transmitting film) having a thickness of 2 μm formed on a Si (100) substrate by rf (high frequency) magnetron sputtering. An X-ray mask material was obtained having a thickness of μm.

The sputter target is a sintered body containing tantalum, silicon, and boron at an atomic ratio (Ta / Si / B) of 0.70 / 0.15 / 0.15. The sputtering gas was argon, and the argon flow rate was 51.0 cc / min. Sputtering conditions are rf power
The power was 400 W (8.64 W / cm ² ) and the sputtering gas pressure was 2.38 Pa. The temperature at the start of the deposition was room temperature.

The X-ray absorbing film produced under the above conditions is ESCA (Electron S
According to pectoroscopy for Chemical Analysis), from the same composition ratio as the target, this composition ratio was almost constant in the depth direction of the film, and it was confirmed that no impurities were contained. Is in the microcrystalline state (grain size 20n
m) and the stress is the measurement limit (1 × 10 ⁸ dyn / cm ² )
It was the following.

Next, after cleaning the surface of the X-ray absorbing film, a resist for electron beam irradiation was applied, and a resist pattern having a line width of 0.25 μm was formed by the electron beam. Further, the resist pattern was transferred to an X-ray absorbing film by reactive ion beam etching to form a pattern having a line width of 0.25 μm. The upper surface and the wall surface of the pattern formed at this time were slightly inferior to Examples 1 to 19 in terms of smoothness.

[Effects of the Invention] As described above, according to the present invention, an X-ray mask material having a small internal stress and having an excellent X-ray absorbing film is provided.

Further, according to the present invention, there is provided an X-ray mask having an extremely fine pattern of, for example, 0.25 μm or less using the above-mentioned X-ray mask material.

Continuation of front page (56) References JP-A-2-2109 (JP, A) JP-A-59-14638 (JP, A) JP-A-61-245525 (JP, A) JP-A-62-86723 (JP, A) , A) Patent 2642724 (JP, B2) JP-B 5-19975 (JP, B2) Vac, Sci. Techno l. B7 (6), (1989) PP. 1561−1564 (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027 G03F 1/16

Claims (3)

(57) [Claims] 1. An X-ray mask material comprising an X-ray transmission film and an X-ray absorption film sequentially provided on a substrate, wherein the X-ray absorption film contains tantalum, silicon and boron. . 2. The X-ray absorbing film has a general formula of Ta _x Si _{(1-x) y} B _{(1-x) (1-y)} (where 0.75 <x <0.85 and 0 <y <1). The X-ray mask material according to claim 1, wherein 3. An X-ray mask obtained by forming an X-ray absorption film of the X-ray mask material according to claim 1 into a fine pattern.