JPH11209840A - Alloy and its production, x-ray mask and its production, and semiconductor device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an X-ray absorber material combining high X-ray stopping power, amorphous structure, and low stress characteristic with high reproducibility. SOLUTION: A Ta-Ge-Re alloy film is used as an X-ray absorber 1. The Ta-Ge-Re alloy film is an amorphous film having high X-ray stopping power and also has high reproducibility of stress at the time of sputtering film formation. The stress of the Ta-Ge-Re film can be easily controlled to a low value by regulating an alloy composition and a sputter gas pressure. Further, stress can also be control led by means of annealing treatment after thin film formation. By applying this Ta-Ge-Re film to the X-ray absorber 1, a high precision X-ray mask minimal in position strain can easily be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alloy material thin film, an X-ray mask using the same, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, X-ray lithography has been used to form fine patterns. X-ray lithography has features such as a short wavelength of X-rays to be used and an easy depth of focus. Particularly, formation of a fine pattern of about 100 nm or less or formation of a pattern having a large aspect ratio. Suitable for forming. X-ray lithography is applied not only to the manufacture of LSIs such as memories and logics, but also to the manufacture of liquid crystal panels, CCDs, thin-film magnetic heads, and micromachines.

In X-ray lithography, a pattern is transferred by irradiating a wafer having a surface coated with a resist with X-rays through an X-ray mask. Specifically, an X-ray mask having an X-ray absorber pattern corresponding to a semiconductor device pattern to be formed is arranged close to a wafer surface coated with an X-ray resist, and X-rays are irradiated from the back of the X-ray mask. By irradiating and exposing the pattern on the X-ray mask to the X-ray resist on the wafer, the pattern can be transferred. This X-ray mask has a structure in which an X-ray absorber having large X-ray absorption is provided on an X-ray transmission film (hereinafter, membrane), and the periphery of the membrane is supported by a support frame such as a silicon substrate and glass. Normal.

FIG. 1 shows an example of the configuration of an X-ray mask.
Silicon nitride (SiN), silicon carbide (Si
A membrane 2 made of a thin film such as C) or diamond (C) is supported by a silicon substrate 3 and a support frame 4 made of SiC or quartz glass.
An X-ray absorber 1 on which a desired pattern is formed is provided on the upper side. Conventionally, as the X-ray absorber 1, a single metal material such as tungsten (W) or tantalum (Ta) has been widely used.

Next, a conventional X-ray mask making process will be briefly described with reference to FIG. First, a thin film of SiC or the like which becomes the membrane 2 is deposited on the both surfaces of a silicon substrate 3 having a thickness of 1 to 2 mm by a CVD method to a thickness of about 1 to 2 μm. next,
A support frame 4 made of glass or SiC having a thickness of about 5 mm is adhered to the outer peripheral portion of the back surface of the Si substrate 3 using an adhesive such as an epoxy resin (FIG. 2A). Next, anisotropic etching (back-etch) of Si using an aqueous KOH solution or the like
A predetermined area is removed from the back surface of the i-substrate 3 to form the membrane 2 (FIG. 2B). Subsequently, the X-ray absorber 1 is formed on the membrane 2 by sputtering.
(C)). Thereafter, the X-ray absorber is patterned by dry etching, and an X-ray mask having a desired pattern is completed.

In the method of manufacturing an X-ray mask shown in FIG.
Although the back etching of the silicon substrate is performed before the formation and patterning of the X-ray absorber, the order may be reversed, and the back etching of the silicon substrate may be performed after the formation of the X-ray absorber.

[0007]

To form a fine pattern of a semiconductor device by X-ray lithography,
The following conditions are required for an X-ray absorber used for an X-ray mask.

First, it has a high X-ray stopping power (corresponding to mass absorption coefficient × density) so that sufficient contrast can be obtained in X-ray exposure. In particular, X
It is necessary to have a large stopping power for X-rays having a wavelength of about 1 nm, which is generally used for X-ray lithography. If the X-ray stopping power is low, the thickness of the X-ray absorber formed on the membrane must be increased, and in this case, fine patterning of the X-ray absorber becomes extremely difficult. Further, when the film thickness of the X-ray absorber increases, the pattern blur at the time of exposure increases,
Problems such as difficulty in controlling the stress occur.

Second, it is required that the stress is as small as possible and that the controllability and stability are high. When a film serving as an X-ray absorber is formed on the membrane, if the internal stress is large, the positional accuracy is deteriorated during patterning, and the semiconductor device pattern to be exposed / transferred is shifted. Therefore, the internal stress of the X-ray absorber must be as close to zero as possible over the entire surface of the mask. Further, in consideration of the productivity of the X-ray mask, it is not enough to simply make the stress close to zero, and it is necessary to realize it with good reproducibility.
Further, since the X-ray mask is used repeatedly, stress stability is also required.

Third, the material used for the X-ray absorber is required to have a dense crystal structure. Many metal materials used as X-ray absorbers become polycrystalline films such as columnar structures when formed by sputtering or the like. When such a polycrystalline film is patterned, a grain boundary of a crystal appears on a side wall, and the pattern side surface is roughened. In such a case, it becomes impossible to form a desired semiconductor device pattern, which is an obstacle to miniaturization.

In addition to the above, it is necessary that the dry etching characteristics at the time of patterning be good and that it be chemically stable.

However, the conventional X-ray absorber has a problem that all of these conditions cannot be satisfied.

Conventionally, W and Ta, which have been widely used, have been applied to the X-ray absorber as the first condition, that is, a material having a sufficient X-ray stopping power. But,
The second and third conditions cannot be sufficiently satisfied, and their application is becoming more difficult with miniaturization of semiconductor devices.

That is, when W and Ta are formed by a sputtering method, a polycrystalline film having a columnar structure is formed. Therefore, when a fine pattern is formed, crystal grain boundaries appear on the side walls of the pattern and the pattern side walls are roughened, which is an obstacle to achieving a desired pattern size.

The stress of the W or Ta film is greatly affected by the conditions for film formation by the sputtering method, that is, the film formation pressure (sputter gas pressure), the film formation temperature, and the like. For example, as shown in FIG. 4, the stress of the Ta film greatly varies from a compressive stress to a tensile stress depending on the sputtering gas pressure. Here, it is particularly important that the stress change near the point where the stress becomes zero is sharp. That is, even if the film is formed under the condition that the stress is once set to zero, the stress changes greatly even if the film forming condition slightly changes, and the reproducibility is extremely deteriorated.

In the case of sputtering of W or Ta, since the film stress is affected by the film forming temperature, if there is a temperature difference between the center of the mask and the vicinity of the support frame, the stress becomes non-uniform. There are also problems. To solve this, the back surface of the membrane is filled with He or the like to control the temperature, the temperature of the support frame portion and the membrane portion are controlled independently, and the temperature of the entire vacuum chamber of the film forming apparatus is strictly controlled. Countermeasures were required, and special measures were required for the film forming apparatus. That is, there is a problem that it is not easy to obtain in-plane uniformity of stress.

In order to solve mainly the problem of the crystal structure among the problems of W and Ta, many materials have been proposed so far.

First, "Journal of Vacuum Science and Technology, 1989, B7
Vol. 6, No. 1, pp. 1561 (M. Sugihara, et al, J. V.
ac.Sci. Tecnol. B7 (6) , 1561, 1989) "The Ta ₄ B
"The Japanese Journal of Applied
Physics, 1990, vol. 31, p. 4210 (H.
Yabe, et al, Jpn. J. Appl. Phys. 31, 4210, 199
No. 0) ", it has been proposed to use WTiN as an X-ray absorber of an X-ray mask. This Ta ₄ B
Since WTiN and WTiN have an amorphous structure, the problem of the roughness of the pattern side wall surface caused by the aforementioned polycrystalline structure can be solved.

However, in these alloys, Ta
Alternatively, B, Ti and N contained in W are elements having low X-ray stopping power. Therefore, when the alloy is used for an X-ray absorber, a new problem arises in that the film thickness required for obtaining a sufficient contrast in X-ray exposure is larger than a single element such as W or Ta.

Another material used for the X-ray absorber is Ta.
And an alloy of Al, Ti, Si, and Mo has also been proposed (Japanese Patent Application No. 63-146546). But Ta and A
In the case of an alloy of 1, Ti, and Si, there is a problem that the X-ray stopping power is low. In the case of an alloy of Ta and Mo, since the film structure has a columnar polycrystalline structure, there is no improvement in the crystal structure.

The present applicant has also proposed a novel X-ray absorber having a high X-ray stopping power and an amorphous structure.
Ge was proposed (Japanese Patent Laid-Open No. 9-190958).

Amorphous TaG formed by sputtering
Since e has an amorphous structure over a wide Ge composition ratio, there is no problem in crystal structure such as roughness of the pattern side wall surface. Ge has a mass absorption coefficient of Al, Ti,
Since it is larger than Si or the like, the above Ta and Al, Ti, S
It is more advantageous than the alloy with i in terms of X-ray absorption.

However, the TaGe alloy has a problem that stress reproducibility is poor. That is, when a film is formed in a low gas pressure region (about 0.25 to 0.5 Pa), the film has a relatively large compressive stress, although the dependency of the stress on the sputter gas pressure is small and the reproducibility of the stress is high. Can only be formed. In addition, the high gas pressure region where the stress is close to zero (0.8
(Approximately 1 Pa), the dependency of the stress on the sputtering gas pressure is large and the reproducibility is poor. That is, it was difficult to obtain a low stress film with good reproducibility even with a TaGe alloy.

As described above, the X-ray absorber materials used and proposed up to now cannot satisfy all the requirements required for the X-ray absorber.

Here, an object of the present invention is to provide a condition required for an X-ray absorber, that is, to have a high X-ray absorbing ability,
It is an object of the present invention to provide a novel alloy material which satisfies all conditions such as a low stress film can be formed with good reproducibility and a dense crystal structure, and a method for producing the same. It is another object of the present invention to disclose an X-ray mask using the alloy material and a method for manufacturing the same, and to provide a method for manufacturing a semiconductor device capable of forming a fine pattern with high accuracy.

[0026]

The present invention provides at least T
Disclosed are alloys containing a, Ge, and Re. In the alloy of the present invention, it is desirable that the total composition ratio of Ta, Ge and Re is 95 atomic% or more, or that the alloy is composed of only Ta, Re and Ge. In the alloy of the present invention, the Ge composition ratio is preferably in the range of 1 to 30 atomic% and the Re composition ratio is in the range of 3 to 60 atomic%. It is effective that the alloy of the present invention has an amorphous structure. The alloy disclosed by the present invention can be in the form of a thin film.

Further, the alloy of the present invention comprises Ta, Ge and R
A thin film can be formed over a substrate by a sputtering method using a target containing e.

The X-ray mask of the present invention is an X-ray mask having an X-ray absorber selectively formed on an X-ray transmitting film, wherein the X-ray absorber is formed of the alloy. It is characterized by the following. Further, the present invention discloses a method for manufacturing an X-ray mask including a step of forming a thin film made of the alloy on an X-ray permeable film by a sputtering method using a target containing Ta, Ge and Re. The method of manufacturing an X-ray mask may include a step of annealing the thin film after the step of forming the thin film.

Further, the present invention includes an X-ray exposure step of transferring an X-ray absorber pattern onto a resist on a substrate by irradiating X-rays through the X-ray mask using the X-ray mask. And a semiconductor device manufactured by the present manufacturing method.

[0030]

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

(First Embodiment) In a first embodiment of the present invention, an X-ray mask is manufactured by depositing a TaGeRe film on a substrate such as SiN or SiC used as a membrane and patterning the TaGeRe film. did. TaGeRe
Is formed by a sputtering method.

The final structure of the X-ray mask manufactured in this embodiment is the same as that shown in FIG. 1 described as the prior art, except that the X-ray absorber is made of a TaGeRe alloy. I have. That is, as shown in FIG.
A membrane 2 made of a thin film of SiN, SiC or C is supported by a silicon substrate 3 and a support frame 4 made of SiC or quartz glass, and an X-ray made of a TaGeRe film having a desired pattern formed on the membrane 2. An absorber 1 is provided.

The manufacturing process of the X-ray mask according to the present embodiment includes a method of performing back etching of the silicon substrate before the formation of the X-ray absorber and a method of manufacturing the silicon substrate after the formation of the X-ray absorber as described in the prior art. Any method of performing back etching of the substrate may be used.

A method of forming a TaGeRe alloy and its characteristics will be described.

In this embodiment, the TaGeRe alloy is formed by sputtering. As the sputtering apparatus, an ordinary RF sputtering apparatus that discharges a sputtering gas by applying a high frequency power of 13.56 MHz was used. Xe was used as a sputtering gas. An alloy target obtained by mixing and sintering Ta, Re, and Ge was used as a sputter target. By changing the mixing ratio of each element in this target, the T
The composition ratio of the aGeRe film can be easily controlled.

The sputtering apparatus used for TaGeRe film formation is not limited to the above RF sputtering apparatus. In addition to this, all sputtering apparatuses capable of forming a metal film, such as a DC sputtering apparatus, are applicable. In addition, the sputtering device has a special device for controlling the stress,
That is, it is not particularly necessary to make the vacuum chamber ultra-high vacuum, control the temperature of the chamber wall, or control the temperature of the substrate (membrane). In this embodiment, Xe is used as a sputtering gas, but may be replaced with another gas such as Ar. However, Ar and X are used as sputtering gases.
Compared with the case where e was used, Xe had a larger atomic radius, so the amount of gas taken into the film was smaller, and Xe was smaller.
A film having good stress control, stability, density and the like of the line absorber can be obtained.

As for the sputter target for forming the TaGeRe film, in addition to the target obtained by mixing and sintering each of the above-described elements, one of the three elements remaining in the target obtained by sintering two of the three elements is combined. A mosaic-like target or a mosaic-like target in which two types of elements remaining in a target of one of the three elements are combined can also be used.

The TaGeRe film formed by the sputtering method has an amorphous structure over a wide composition ratio. The composition ratio of an amorphous structure is generally in the range of 1 to 30 atomic% of Ge and 3 to 60 atomic% of Re. (In the present specification, the composition of the alloy is in the form of the atomic ratio of each element or the atomic%. ). Therefore, TaG film formed in this composition range
Even if the eRe film is patterned with a size of 100 nm or less for application of an X-ray mask, it is not roughened by the crystal grain boundaries, and the side wall becomes very smooth.

FIG. 4 shows a TaGe film formed by a sputtering method.
4 is a graph showing the relationship between the stress of the Re film and the sputter gas pressure using the composition ratio as a parameter. In FIG. 4, lines denoted by reference numerals 6, 7, and 8 are Ta, Ge, and Re, respectively.
Of 1: 0.24: 0.96, 1: 0.24:
It shows the stress of the TaGeRe film of 0.75, 1: 0.24: 0.12. The substrate temperature during the TaGeRe film formation is room temperature, and the film thickness is 0.5 μm. For reference, the stress of the Ta single metal film is also shown as a line indicated by reference numeral 5 in FIG. As can be seen from this figure, the stress of the TaGeRe film tends to move to the tensile stress side as the Re composition increases. Also,
As the pressure of the sputtering gas increases, the stress changes from a compressive stress to a tensile stress.

Here, as can be seen from FIG. 4, TaGe
The Re alloy has a small amount of change in stress with respect to a change in sputter gas pressure in a region where a film having a lower stress than that of Ta alone can be obtained (that is, the slope of the graph is small). Therefore, there is an advantage that the fluctuation of the sputtering gas pressure has little effect on the reproducibility of the stress, and the unevenness of the in-plane distribution of the stress due to the fluctuation of the gas pressure is also reduced. Further, the stress of the TaGeRe film is hardly affected by the film forming temperature, the impurities in the film forming apparatus, and the wall temperature of the film forming apparatus, which affect the stress of the conventional X-ray absorber material. Therefore, a uniform stress distribution can be obtained even with an inexpensive film forming apparatus without an ultra-high vacuum sputtering chamber, chamber wall temperature control, membrane temperature control, and the like.

As described above, by controlling the composition ratio of the TaGeRe film and the sputter gas pressure at the time of film formation, it is possible to realize low stress with good reproducibility. Where TaGeR
The composition ratio of the e film can be controlled within the composition range where the above-mentioned amorphous structure can be obtained, but a desirable composition range is a Ge composition of 10 to 30% and a Re composition of 5 to 50%.

Re and Ge have a mass absorption coefficient of X-rays at a wavelength of about 1 nm, which is used in the same-magnification X-ray exposure, which is higher than that of a conventional T-ray.
It is larger than Ta itself, as well as B, Ti, etc. used as an additive to a and the like. Furthermore, Ta
When an alloy is formed, the density is 16 g / cm ³ or more (for example, 16.2 g / cm ³ ), which is about the same as that of Ta alone. As a result, the X-ray stopping power of the TaGeRe alloy becomes larger than that of the metal or alloy used as the conventional X-ray absorber, and the same contrast can be obtained with a thinner film thickness than the conventional material. Therefore, workability and stress controllability at the time of patterning are improved, and the total stress of the film is smaller than that of the conventional X-ray absorber.

Furthermore, since the TaGeRe film forms a very thin passivation film on the surface even when exposed to the atmosphere, the chemical stability is high, and the dimensional change of the pattern due to oxidation after the formation of the X-ray absorber pattern hardly occurs. . Therefore, even in an oxygen ashing step for stripping the resist after patterning, the change in stress due to oxidation is as very small as 10 MPa or less. Further, even if the cleaning with acid and alkali is performed, the etching amount is 1 nm / min or less and there is no change in stress. This T
The thickness of the passivation film on the surface of the aGeRe film is the same as that of the conventional single Ta.
It is thinner than a passivation film such as TaGe or TaGe, and is advantageous in terms of dimensional and stress changes after patterning and precise exposure of pattern edges during X-ray exposure.

As described above, the TaGeRe film of the present invention is
By using it as a line absorber, all the problems of the conventional X-ray absorber material are solved, and a practical X-ray mask is completed. By performing X-ray exposure using this,
This makes it possible to greatly improve the controllability and reproducibility of forming a fine pattern in a semiconductor device.

In addition, even if it contains several% or less of other elements in addition to the three elements of Ta, Ge, and Re, there is almost no change in characteristics, and it is useful as an X-ray absorber. For example, even if it contains 5% or less of Ti, Hf, W, or Si, there is almost no problem when used for an X-ray mask.

Example 1 In this example, an X-ray mask was manufactured by patterning the X-ray absorber 1 after back etching the silicon substrate 3. The manufacturing process of the present embodiment is almost the same as the process described with reference to FIG.
The only difference is that a GeRe film is formed.

Referring to FIG. 2, an X-ray mask forming process of this embodiment will be briefly described. First, SiC or the like serving as the membrane 2 is deposited on both surfaces of a silicon substrate 3 having a thickness of 1 to 2 mm by a CVD method to a thickness of about 1 to 2 μm. Next, a support frame 4 made of glass or SiC having a thickness of about 5 mm is adhered to the outer peripheral portion of the back surface of the Si substrate 3 using an epoxy resin (FIG. 2).
(A)). Next, a predetermined region is removed from the back surface of the Si substrate 3 by anisotropic etching of Si (back etching) using a KOH aqueous solution or the like to form the membrane 2 (FIG. 2).
(B)). Subsequently, an X-ray absorber 1 made of a TaGeRe film is formed on the membrane 2 by a sputtering method (FIG. 2C). Then, X
X having a desired pattern by patterning the line absorber
The line mask is completed.

The composition ratio of the TaGeRe film formed in this embodiment is Ta: Ge: Re = 1: 0.24: 0.80 (T
a = 49.0%, Ge = 11.8%, Re = 39.2
%). A TaGeRe film having this composition ratio is set to 0.6 Pa
By forming the film under the conditions of the sputtering gas pressure, a film with almost zero stress could be formed over the entire surface of the substrate.

(Embodiment 2) In this embodiment, unlike the process shown in FIG. 2 described in Embodiment 1, a back etching step of a silicon substrate is performed after forming an X-ray absorber on a membrane. The method was adopted. Hereinafter, an X-ray mask manufacturing process according to the present embodiment will be described with reference to FIG.

First, a thin film of SiN, SiC or the like having a thickness of 1 to 2 μm to be the membrane 2 is formed on both surfaces of the silicon substrate 3 (FIG. 3A). Subsequently, a TaGeRe film as the X-ray absorber 1 is formed on the SiN or SIC film on the surface of the silicon substrate 3 by a sputtering method (FIG. 3).
(B)). Subsequently, the silicon substrate 3 is anisotropically etched using a solution such as KOH to form the membrane 2. Further, a thickness of 5 mm is applied to the outer peripheral portion of the back surface of the silicon substrate 3.
A support frame 4 made of glass or the like is bonded with an epoxy resin (FIG. 3C). Finally, by dry etching using an etching gas such as SF6 or Cl ₂ which was processed into a predetermined pattern by applying a resist on TaGeRe film, the further resist as a mask TaGe
The Re film is processed, and the X-ray absorber 1 is patterned (FIG. 3D). Through the above steps, an X-ray mask using the TaGeRe film as the X-ray absorber is completed. The composition ratio and the film forming conditions of the TaGeRe film in this embodiment are the same as those in the first embodiment.

According to the manufacturing method of the X-ray mask employed in this embodiment, unlike the first embodiment, the X-ray absorber is formed on the silicon substrate, so that the stress of the X-ray absorber is reduced in each step. There is an advantage that accurate measurement can be performed. However, when forming the membrane by performing back etching of the silicon substrate after forming the X-ray absorber, the support frame is distorted due to the tensile stress of the membrane film, and the stress of the membrane and the X-ray absorber changes. Sometimes. In this case, the X-ray absorber is formed in advance with a tensile stress greater than the target stress, or the pattern data is corrected by estimating the amount of pattern position distortion from the stress after the film formation, or the like. It is possible to make the line mask highly accurate.

(Second Embodiment) TaGeR of the present invention
By subjecting the e-alloy film to an annealing treatment after the film formation, the stress in the film can be adjusted. In this embodiment, an example will be described in which a TaGeRe film is formed as an X-ray absorber, the stress is adjusted by annealing, and a low-stress X-ray mask is formed. The formation of the TaGeRe film itself can be performed in the same manner as in the first embodiment.

FIG. 5 is a graph showing the relationship between the change in stress, the annealing temperature and the annealing time when the TaGeRe film is annealed in a vacuum. As can be seen from FIG.
By performing the annealing treatment at a temperature of about 00 ° C. or more, the film stress changes to the tensile side immediately after the film formation. The degree of this change increases as the annealing temperature increases. The stress change due to annealing saturates in about 5 to 15 minutes. The annealing atmosphere is changed from vacuum to Ar, X
Even if the atmosphere is changed to an inert gas atmosphere such as e or N ₂ , exactly the same result can be obtained.

By utilizing this phenomenon, a compressive stress film is formed in a low gas pressure region in which a film can be formed with good reproducibility because the dependency of stress on the sputtering gas pressure during film formation is small (the slope of the graph in FIG. 4 is small). After that, by performing an annealing process at an appropriate temperature to change the stress to the tensile side, a low stress TaGeRe film with high reproducibility can be formed.

In the case where the TaGeRe film having undergone the annealing treatment to thereby saturate the stress change is used, the temperature of the mask may be lowered in the resist step or the etching step in the X-ray mask manufacturing process, or when the mask is used for exposure. The stress does not change even when it rises, and an X-ray mask with higher stress stability can be obtained. In a normal manufacturing process, the temperature of the X-ray mask stays at about 150 ° C. or less even if it rises. However, annealing at a temperature higher than this increases the thermal margin, which is advantageous.

As described above, the annealing of the TaGeRe film makes it possible to adjust the stress and improve the thermal stability in the process. From this viewpoint, it is desirable that the annealing process be performed immediately after the TaGeRe film is formed. However, if the purpose is only to adjust the stress, the annealing may be performed after the patterning step or the like is performed.

(Embodiment 3) In this embodiment, similarly to Embodiment 1, an X-ray mask is manufactured by using a process of forming an X-ray absorber after back-etching a silicon substrate as shown in FIG. did. Hereinafter, the manufacturing process will be briefly described with reference to FIG.

The steps up to the step of back etching the silicon substrate 3 are performed in exactly the same manner as in the first embodiment (FIGS. 2A to 2A).
(B)). Subsequently, TaGeRe was used as the X-ray absorber 1.
The film is formed by a sputtering method. TaG to be deposited here
The composition ratio of the eRe film is Ta: Ge: Re = 1: 0.2
4: 0.75 (Ta = 50.2%, Ge = 12.1%,
Re = 37.7%). The sputtering gas pressure during film formation was 0.6 Pa, which was the same as in Example 1. Here, the composition ratio of the TaGeRe film formed in the present embodiment is slightly smaller than that in the first embodiment. Therefore, the stress of the film becomes a compressive stress of about 80 MPa over the entire surface of the film.

Next, annealing of the TaGeRe film is performed. Annealing conditions were 400 ° C. for 10 minutes in a vacuum. By this annealing treatment, the stress of the film is about 80MP.
It changes to the pulling side by about a. As a result, the compressive stress immediately after the film formation and the stress change due to the annealing cancel each other, and a low-stress TaGeRe film having a stress close to zero is formed.

Thereafter, similarly to the first embodiment, TaGeRe
The X-ray absorber 1 made of a film is patterned to complete an X-ray mask.

(Embodiment 4) In the process of back etching the silicon substrate after forming the same X-ray absorber as in Embodiment 2, it is also possible to perform an annealing process after the TaGeRe film formation as follows.

First, a film of SiN, SiC or the like to be the membrane 2 is formed on both surfaces of the silicon substrate 3. After that, a TaGeRe film is formed as the X-ray absorber 1 by a sputtering method, and then this is annealed. The subsequent steps are performed in exactly the same manner as in Example 2, whereby the X-ray mask is completed.

In this embodiment, as in the third embodiment,
At the time of film formation, a TaGeRe film is formed so as to have a compressive stress. For example, if the composition ratio is Ta: Ge: Re = 1:
By forming a TaGeRe film of 0.24: 0.75 at a sputtering gas pressure of 0.6 Pa, about 8
An X-ray absorber 1 having a compressive stress of 0 MPa is obtained.
On the other hand, for example, by performing an annealing process at 400 ° C. for 10 minutes in a vacuum, the film stress is changed to the tensile side, and an X-ray absorber having a very low stress can be obtained.

As described above, in the TaGeRe alloy of the present invention, the composition ratio, the film forming conditions (sputter gas pressure), and the annealing conditions after the film formation are set as described in the first and second embodiments. By controlling, a thin film with low stress can be obtained with excellent controllability. Also, by applying this to an X-ray absorber, an X-ray mask with extremely small positional distortion can be obtained.

The gist of the present invention is to use a TaGeRe film as the X-ray absorber 1 in the X-ray mask. Of course, other members in the X-ray mask, that is, the membrane 2, the silicon substrate 3, the support frame 4, and the like can be replaced with equivalents.

(Third Embodiment) A fine pattern is formed by performing X-ray lithography using the X-ray mask having a TaGeRe film as the X-ray absorber described in the first and second embodiments. Can be manufactured with good reproducibility.

A semiconductor device (a semiconductor chip such as a memory or a logic, or a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, or the like) performs a pre-process of forming an actual circuit on a wafer and forms and packages the wafer into chips. It is commercialized through a post process. Of these, the wafer process includes various steps such as formation of an insulating film, formation of an electrode, and ion implantation. In each step, lithography is a process for forming a pattern on a substrate according to a device design drawing. In the lithography process, resist application, exposure, and development are performed, and a resist pattern is formed on the substrate.

The X-ray mask using the TaGeRe alloy of the present invention as an X-ray absorber is effective in all cases where X-rays are used for exposure in this lithography.
The effect is high when a fine device pattern of about 13 μm or less is formed or when a pattern having a large aspect ratio (> about 5) is formed.

In a semiconductor device, the pattern of the next layer is superimposed on the pattern formed on the previous layer, and its accuracy is required to be a fraction of the minimum pattern line width. Here, the first and second embodiments (Examples 1 to 5)
In the X-ray mask disclosed in 4), since the stress of the X-ray absorber is highly controlled, positional distortion is extremely small as compared with the conventional X-ray mask. For example, by using SiC for the X-ray transmission film, the area of 35 mm square is covered by 50% with a coverage of ± 5
The maximum positional distortion caused by the X-ray absorber when the X-ray absorber pattern a is formed is 5 nm or less. Therefore, if the X-ray mask of the present invention is used in the above exposure process, a pattern faithful to a device design drawing can be created.

As described above, by performing the X-ray lithography using the X-ray mask using the TaGeRe alloy of the present invention, it becomes possible to manufacture a semiconductor device having good characteristics at a high yield.

In the embodiment of the present invention, an example in which the TaGeRe alloy thin film of the present invention is applied to an X-ray absorber of an X-ray mask has been described, but the use of the TaGeRe alloy thin film is limited to an X-ray mask. is not. That is,
It goes without saying that the TaGeRe alloy thin film of the present invention is useful in applications where low stress characteristics are required.

[0072]

As described above, the TaGeRe alloy of the present invention is a
It has a high X-ray stopping power as compared with a line absorber material. Also,
A thin film having an amorphous structure can be obtained in a wide alloy composition range. Further, by adjusting the composition ratio and the sputter gas pressure during film formation, a low-stress film can be obtained with very high reproducibility. Due to these characteristics, the TaGeR of the present invention
The e-alloy thin film is very effective as an X-ray absorber in an X-ray mask.

The stress of the TaGeRe film is hardly affected by parameters other than the sputtering gas pressure. Therefore, the TaGeRe film of the present invention has a feature that a low stress film can be formed with good reproducibility even with an inexpensive film forming apparatus.

Further, the stress of the TaGeRe film of the present invention can be controlled by annealing after the film is formed. Thereby, the reproducibility of stress is further improved.

By performing lithography using an X-ray mask having a TaGeRe film having the above characteristics as an X-ray absorber, a semiconductor device having a pattern of about 0.1 μm or less can be manufactured at a high yield. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an X-ray mask of the present invention.

FIG. 2 is a diagram illustrating a manufacturing process according to Examples 1 and 3 of the present invention.

FIG. 3 is a diagram illustrating a manufacturing process according to Embodiments 2 and 4 of the present invention.

FIG. 4 is a diagram showing the relationship between the stress of the TaGeRe film of the present invention and the sputtering gas pressure, using the composition ratio as a parameter.

FIG. 5 is a diagram showing a change in film stress when a TaGeRe film of the present invention is annealed in a vacuum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 X-ray absorber 2 Membrane 3 Silicon substrate 4 Support frame 5 Shows the stress of Ta 6 Shows the stress of the TaGeRe film whose composition ratio is 1: 0.24: 0.96 7 The composition ratio is 1: 0.24: 0 8 indicates the stress of a TaGeRe film having a composition ratio of 1: 0.24: 0.12.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C22C 45/00 H01L 21/30 531M

Claims (12)

[Claims] An alloy containing at least Ta, Ge and Re. 2. The composition ratio of Ta, Ge and Re is 9
The alloy according to claim 1, which is at least 5 atomic%. 3. An alloy comprising Ta, Re and Ge. 4. The alloy according to claim 1, wherein the Ge composition ratio is in the range of 1 to 30 at% and the Re composition ratio is in the range of 3 to 60 at%. 5. The alloy according to claim 1, which has an amorphous structure. 6. The alloy according to claim 1, wherein the alloy is in the form of a thin film. 7. An X-ray mask having an X-ray absorber selectively formed on an X-ray permeable film, wherein the X-ray absorber is formed of the alloy according to any one of claims 1 to 5. An X-ray mask, comprising: 8. An alloy according to claim 1, wherein a thin film made of the alloy according to claim 1 is formed on a substrate by sputtering using a target containing Ta, Ge and Re. Production method. 9. A method for forming a thin film made of the alloy according to any one of claims 1 to 5 on a X-ray permeable film by sputtering using a target containing Ta, Ge and Re. A method for manufacturing an X-ray mask, comprising: 10. The method according to claim 9, further comprising a step of annealing the thin film after the step of forming the thin film. 11. An X-ray exposure step of transferring an X-ray absorber pattern to a resist on a substrate by irradiating X-rays through the X-ray mask using the X-ray mask according to claim 7. Semiconductor device manufacturing method. 12. An X-ray exposure step of transferring an X-ray absorber pattern onto a resist on a substrate by irradiating X-rays through the X-ray mask using the X-ray mask according to claim 7. A semiconductor device on which is formed.