KR19990068190A - Improved alloy and method of preparing the same as well as x-ray mask and method of forming the same in addition semiconductor device and method of forming the same - Google Patents

Abstract

A TaGeRe alloy film is used as the X-ray absorber 1. The TaGeRe alloy film is an amorphous film having a high X-ray stop function, and also has high reproducibility of stress when forming a sputtered film. The stress of the TaGeRe film can be easily controlled at low stress by adjusting the alloy composition and the sputter gas pressure. The stress can also be controlled by an annealing treatment after film formation. By applying this TaGeRe film to the X-ray absorber 1, an X-ray absorber material having a high X-ray blocking function, an amorphous structure, and a high reproducibility-low stress characteristic can be easily obtained by easily obtaining a high-precision X-ray mask with low positional deviation. Acquire.

Description

Alloy and its manufacturing method and X-ray mask and its manufacturing method and semiconductor device and its manufacturing method SAME}

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

With the higher integration of semiconductor devices, X-ray lithography can be used to form fine patterns. X-ray lithography has the characteristics that the wavelength of X-rays to be used is short and it is easy to take a large depth of focus, and it is especially preferable for formation of a fine pattern of about 100 nm or less, or formation of a pattern with a large aspect ratio. X-ray lithography is not limited to the production of LSI such as memory and logic, but is also applied to the manufacture of liquid crystal panels, CCDs, thin film magnetic heads, and even micromachines.

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

1 shows an example of the configuration of an X-ray mask. The membrane 2 made of a thin film of silicon nitride (SiN), silicon carbide (SiC) or diamond (C) is supported by a silicon substrate 3 and a support frame 4 made of SiC or quartz glass or the like. On the membrane 2, an X-ray absorber 1 having a predetermined pattern is provided. 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 manufacturing process will be briefly described with reference to Figs. 2A to 2D. First, a thin film of SiC or the like, which becomes the membrane 2, is deposited on both surfaces of the silicon substrate 3 having a thickness of 1 to 2 mm by about 1 to 2 m. Next, a support frame 4 such as glass or SiC having a thickness of about 5 mm is bonded to the outer circumferential portion of the back surface of the Si substrate 3 using an adhesive such as an epoxy resin (see FIG. 2A). Then, by anisotropic etching (back etching) of Si using a KOH aqueous solution or the like, a predetermined region is removed from the back surface of the Si substrate 3 to prepare a membrane 2 (see FIG. 2B). Next, the X-ray absorber 1 is formed on the membrane 2 by the sputtering method (see FIG. 2C). Thereafter, the X-ray absorber is patterned by dry etching to complete an X-ray mask having a predetermined pattern.

In the method for manufacturing the X-ray mask shown in Figs. 2A to 2D, the back-etch of the silicon substrate is carried out before the formation and patterning of the X-ray absorber. However, the order of the silicon substrate is reversed after the formation of the X-ray absorber. It is also possible to execute back etch.

In order to perform fine pattern formation of a semiconductor device by X-ray lithography, the following conditions are required for the X-ray absorber used for the X-ray mask.

First, it has a high X-ray blocking function (corresponding to mass absorption coefficient x density) so that sufficient contrast can be obtained in X-ray exposure. In particular, it is necessary to have a large blocking function against X-rays in the vicinity of the wavelength of 1 nm, which is usually used for X-ray lithography. If the X-ray blocking function is small, the thickness of the X-ray absorber film formed on the membrane must be thickened, and in this case, it becomes very difficult to form fine patterning of the X-ray absorber. Moreover, when the film thickness of an X-ray absorber becomes large, the problem that a pattern will become blurred at the time of exposure will increase, and control of a stress will become difficult.

Second, it is required that the stress is as small as possible, and at the same time, its controllability and stability are high. When the film serving as the X-ray absorber is formed on the membrane, if its internal stress is large, its positional accuracy is deteriorated during patterning, and further, a deviation occurs in the semiconductor device pattern exposed and transferred. Therefore, the internal stress of the X-ray absorber should be as close to zero as possible over the entire surface of the mask. In consideration of the productivity of the X-ray mask, it is not enough to simply bring the stress close to zero, and it is also necessary to realize it with good reproducibility. Furthermore, since the X-ray mask is used repeatedly, the stability of the stress is also required.

Third, the material used as the X-ray absorber is required to have a dense crystal structure. Most of the metal materials used as X-ray absorbers become polycrystalline films such as columnar structures when formed by the sputtering method or the like. When the polycrystalline film is patterned, grain boundaries of crystals appear on the sidewalls, thereby causing a phenomenon in which the pattern side is roughened. In such a case, it is impossible to form a predetermined semiconductor device pattern, and it becomes a obstacle to miniaturization.

In addition to the above, it is also necessary to have good dry etching characteristics during patterning, and to be chemically stable.

However, there has been a problem that all of these conditions cannot be satisfied in the conventionally used X-ray absorbers.

Conventionally, W and Ta, which have been widely used in general, have been applied to X-ray absorbers as a material having the first condition, that is, sufficient X-ray low intelligence. However, for the second condition, this cannot be sufficiently satisfied, and application is difficult due to the miniaturization of semiconductor devices.

That is, when W and Ta are formed by the sputtering method, they become a polycrystalline film having a columnar structure. Therefore, when a fine pattern is formed, grain boundaries of the crystal appear on the sidewalls of the pattern, resulting in roughening of the pattern side wall surface, which is obstructive in achieving a desired pattern dimension.

The stress of the W or Ta film is greatly influenced by the conditions of film formation by the sputtering method, that is, film formation pressure (sputter gas pressure), film formation temperature, and the like. For example, the stress of the Ta film varies greatly from the compressive stress to the tensile stress, depending on the sputter gas pressure, as shown in FIG. It is particularly important here that the stress change in the vicinity where the stress becomes zero is sharp. In other words, even if the film is formed under the condition that the stress is zero, the reproducibility is extremely deteriorated because the stress is greatly changed only by a slight fluctuation of the film forming condition.

In addition, in the formation of the sputtered film of W or Ta, since the film stress is affected by the film formation temperature, there is also a problem in that stress unevenness occurs when there is a temperature difference between the central portion of the mask and the vicinity of the support frame. In order to solve this problem, measures such as controlling the temperature by filling the back surface of the membrane with He or the like, independently controlling the temperature of the supporting frame portion and the membrane portion, or strictly controlling temperature of the vacuum assembly of the film forming apparatus are necessary. In addition, a special process is required for the film forming apparatus. That is, there was a problem that it was not easy to maintain in-plane uniformity of stress.

In order to solve the problem of crystal structure mainly among these problems with W and Ta, many materials have been proposed until now.

First, the Journal of vacuum science and technology, 1989, Vol. B7, No. 6, p. 1561 (M. Sugihara, et al, J. Vac. Sci. Tecnol.B7 (6), 1561, 1989), has Ta. _4B , WTiN in Japanese journal of applied physics, 199O, vol. 31, p. 4210 (H. Yabe, et al, Jpn. J. Appl. Phys. 31, 4210, 1990). A proposal has been made to use it as a line absorber Since Ta ₄ B and WTiN have an amorphous structure, the problem of roughening the pattern side wall surface caused by the above-described polycrystalline structure is solved.

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

As another material used for the X-ray absorber, alloys of Ta and Al, Ti, Si, and Mo are also proposed (Japanese Patent Application No. 63-146546). However, in the case of alloys of Ta, Al, Ti, and Si, there is a problem that the X-ray blocking function is low. In the case of the alloy of Ta and Mo, since the film structure has a columnar polycrystalline structure, no improvement on the crystal structure can be found.

The present applicant has also proposed TaGe as a novel X-ray absorber having a high X-ray blocking function and an amorphous structure (Japanese Patent Laid-Open No. 9-190958).

Since amorphous TaGe formed by the sputtering method has an amorphous structure over a large Ge composition ratio, there is no problem in crystal structure such as roughening of the pattern side wall surface. In addition, since the mass absorption coefficient of Ge is larger than that of Al, Ti, and Si, the X-ray absorption function is more advantageous than the alloy of Ta, Al, Ti, and Si described above.

However, TaGe alloys have a problem of poor stress reproducibility. That is, when the film is formed in the low gas pressure range (around 0.25 to 0.5 Pa), only the film having a relatively large compressive stress can be formed, although the stress sputter gas pressure dependency is small and the stress reproducibility is high. Further, in the region of high gas pressure where the stress approaches zero (about 0.8 to 1 Pa), the sputter gas pressure dependency of the stress is large and the reproducibility deteriorates. That is, it was difficult to obtain a low stress film with good reproducibility even in TaGe alloy.

As described above, the X-ray absorber material used or proposed so far cannot satisfy all of the requirements for the X-ray absorber.

Here, the object of the present invention satisfies all the conditions required for the X-ray absorber, that is, having a high X-ray absorption function, being able to form a low stress film with good reproducibility, and having a dense crystal structure. It is to provide a novel alloy material and a method of manufacturing the same. An object of the present invention is to provide an X-ray mask using this alloying 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.

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

2A to 2D are diagrams for explaining the structural processes of the first and third embodiments of the present invention.

3A to 3D illustrate the structural processes of the second and fourth embodiments of the present invention.

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

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

※ Explanation of code for main part of drawing

1: X-ray absorber 2: Membrane

3: silicon substrate 4: support frame

5: stress of Ta

6: stress of TaGeRe film with composition ratio 1: 0.24: 0.96

7: Stress of TaGeRe film with composition ratio 1: 0.24: 0.75

8: Stress of TaGeRe film with composition ratio 1: 0.24: 0.12

The present invention discloses an alloy containing at least Ta, Ge and Re. In the alloy of the present invention, the compositional ratio of Ta, Ge, and Re is 95 atom% or more. Or it is preferable that it consists only of 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 in the range of 3 to 60 atomic%. In addition, it is effective that the alloy of the present invention has an amorphous structure. The alloy disclosed by the present invention can have the shape of a thin film.

Moreover, the alloy of this invention can form a thin film on a board | substrate by the sputtering method using the target containing Ta, Ge, and Re.

The X-ray mask of the present invention is an X-ray mask having an X-ray absorber selectively formed on an X-ray transmissive film, wherein the X-ray absorber is formed of the alloy. Moreover, this invention discloses the manufacturing method of the X-ray mask which has the process of forming the thin film which consists of said alloy on the X-ray permeable film by the sputtering method using the target containing Ta, Ge, and Re. In the manufacturing method of this X-ray mask, it is also possible to have the process of annealing the said thin film after the process of forming the said thin film.

Furthermore, the present invention includes an X-ray exposure process 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. A manufacturing method and a semiconductor device manufactured by the manufacturing method are disclosed.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to drawings.

First embodiment

In the first embodiment of the present invention, an X-ray mask was manufactured by depositing a TaGeRe film on a substrate such as SiN or SiC used as a membrane and patterning it. The sputtering method is used for TaGeRe film formation.

Although the final structure of the X-ray mask manufactured by this embodiment is the same as that shown in FIG. 1 explained as a prior art, the point which comprised the X-ray absorber by TaGeRe alloy differs. That is, as shown in Fig. 1, the membrane 2 made of a thin film such as SiN, SiC or C is supported by a silicon substrate 3 and a support frame 4 made of SiC or quartz glass or the like. On the membrane 2, an X-ray absorber 1 made of a TaGeRe film having a predetermined pattern is provided.

As the manufacturing process of the X-ray mask of the present embodiment, a method of performing back etch on the silicon substrate described in the prior art before forming the X-ray absorber, and performing back etch on the silicon substrate after the X-ray absorber is formed. Any way of doing this is possible.

The film formation method and its characteristics of TaGeRe alloy will be described.

In the present embodiment, the film formation of the TaGeRe alloy was formed by the sputtering method. As the sputter apparatus, a conventional RF sputter apparatus which discharges sputter gas by application of a high frequency power of 13.56 MHz was used. Xe was used as sputter gas. As the sputter target, an alloy target obtained by mixing and sintering Ta, Re, and Ge was used. By changing the mixing ratio of each element in the target, the composition ratio of the formed TaGeRe film can be easily controlled.

On the other hand, the sputtering apparatus used for TaGeRe film formation is not limited to the said RF sputtering apparatus. In addition, any sputtering apparatus capable of forming a metal film, such as a direct current sputtering apparatus, can be applied. In addition, the sputtering device is not particularly required for special studies for controlling stress, that is, to make the vacuum chamber ultra-high vacuum, to control the temperature of the seal wall, or to control the temperature of the substrate (membrane). In addition, although Xe was used as a sputter gas in this embodiment, you may change into other gases, such as Ar. However, compared with the case where Ar and Xe are used as the sputter gas, Xe has a large atomic radius, so the amount of gas to be contained in the film is reduced, so that a film having excellent stress control, stability, density, etc. of the X-ray absorber can be obtained. You can get it.

In addition, regarding the sputter target for TaCeRe film formation, in addition to the target in which the above-mentioned elements are mixed and sintered, a mosaic-shaped target combining one type of element remaining on a sintered target of two elements, or one of three elements The mosaic target etc. which combined the two types of elements which remain in the target of a kind of element can also be used.

The TaGeRe film formed by the sputtering method has an amorphous structure over a large composition ratio. The composition ratio of the amorphous structure is approximately in the range of 1 to 30 atomic% of Ge and 3 to 60 atomic% of Re (in this specification, the composition of the alloy is represented by the type or atomic% of the atomic ratio of each element). . Therefore, the TaGeRe film having a film formed in this composition range is not roughened by grain boundaries even if the pattern is formed at a size of 100 nm or less for the application of the X-ray mask, and the sidewall is very smooth.

4 is a graph showing the relationship between the stress of the TaGeRe film formed by the sputtering method and the sputtering gas pressure as a composition ratio as a parameter. In Fig. 4, lines 6, 7, and 8 represent the stresses of TaGeRe films having the composition ratios of Ta, Ge, and Re of 1: 0.24: 0.96, 1: 0.24: 0.75, and 1: 0.24: 0.12, respectively. In forming these TaGeRe films, the substrate temperature is room temperature and the film thickness is 0.5 탆. Incidentally, for reference, the stress of the Ta group metal film is also shown as a line shown by reference numeral 5 in FIG. As can be seen from this figure, the stress of the TaGeRe film tends to move toward the tensile stress side while increasing the Re composition. In addition, as the pressure of the sputter gas increases, the compressive stress changes from the tensile stress.

As can be seen from FIG. 4, the TaGeRe 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 of a single body is obtained (that is, the slope of the graph is small). Accordingly, there is an advantage that the influence of the variation of the sputter gas pressure on the reproducibility of the stress is small, and the non-uniformity of the in-plane distribution of the stress caused by the variation of the gas pressure is also reduced. In addition, 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. As a result, even in an inexpensive film forming apparatus without ultra-high vacuum sputter chamber, seal wall temperature control, membrane temperature control, or the like, uniform stress distribution can be obtained.

From the above, it is possible to realize low stress with good reproducibility by controlling the composition ratio of the TaGeRe film and the sputter gas pressure at the time of film formation. Here, although the composition ratio of the TaGeRe film can be controlled within the composition range in which the above-described amorphous structure can be obtained, the preferred composition range is 10 to 30% of Ge composition and 5 to 50% of Re composition.

In addition, Re and Ge are mass absorption coefficients of X-rays near 1 nm in wavelength used in equally X-ray exposure, as well as larger than B, Ti and the like, which are conventionally used as additives to Ta and the like. Moreover, the density in the case of forming an alloy with Ta 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 blocking function of the TaGeRe alloy is larger than that of a metal or alloy conventionally used as an X-ray absorber, so that contrast can be obtained with a film thickness thinner than that of a conventional material. Therefore, workability and stress controllability are improved during patterning, and the overall stress of the film is also made smaller than that of the conventional X-ray absorber.

In addition, the TaGeRe film has high chemical stability in order to form a very thin passivation film on the surface even when exposed to the atmosphere, and it is difficult to cause dimensional change of the pattern due to oxidation after the X-ray absorber pattern formation. Therefore, even in an oxygen ashing process for resist stripping after patterning, the stress change due to oxidation is very small, 10 MPa or less. In addition, even if acid and alkali cleaning are performed, etching amount is 1 nm / min or less, and there is no change of stress. The thickness of the passivation film on the surface of the TaGeRe film is thinner than conventional passivation films such as Ta or TaGe, and is advantageous in terms of dimensional and stress changes after patterning and precision exposure of pattern edges during X-ray exposure.

As mentioned above, by using the TaGeRe film of this invention as an X-ray absorber, all the problems with the conventional X-ray absorber material are solved and a substantial X-ray mask is completed. By performing X-ray exposure using this, it becomes possible to significantly improve the controllability and reproducibility of fine pattern formation in a semiconductor device.

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

Example 1

In this embodiment, the X-ray mask was manufactured by patterning the X-ray absorber 1 after performing back etching of the silicon substrate 3. The manufacturing process of this embodiment is almost the same as the process described in Figs. 2A to 2D as the prior art, except that the TaGeRe film is formed as the X-ray absorber 1.

2A to 2D, the X-ray mask preparation process of this embodiment will be briefly described. First, SiC or the like, which is the membrane 2, is deposited on both surfaces of the silicon substrate 3 having a thickness of 1 to 2 mm by CVD. Next, using an epoxy resin, a support frame 4 such as glass or SiC having a thickness of about 5 mm is bonded to the outer periphery of the back surface of the Si substrate 3 (see FIG. 2A). Next, by anisotropic etching (back etching) of Si using a KOH aqueous solution or the like, a predetermined region is removed from the back surface of the Si substrate 3 to prepare a membrane 2 (see FIG. 2B). Subsequently, an X-ray absorber 1 made of a TaGeRe film is formed on the membrane 2 by the sputtering method (see FIG. 2C). Thereafter, the X-ray absorber is patterned by dry etching, and an X-ray mask having a desired pattern is completed.

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

Example 2

This embodiment is different from the process shown in Figs. 2A to 2D described in the first embodiment, and employs a manufacturing method of performing a back-etch process of a silicon substrate after forming an X-ray absorber on a membrane. It was. 3A to 3D, an X-ray mask manufacturing process in the form of the present embodiment will be described.

First, thin films, such as SiN and SiC, having a thickness of 1 to 2 占 퐉 to be the membrane 2 are formed on both surfaces of the silicon substrate 3 (see Fig. 3A). Subsequently, a TaGeRe film is formed on the SiN or SiC film on the surface of the silicon substrate 3 by the sputtering method as the X-ray absorber 1 (see Fig. 3B). Subsequently, the silicon substrate 3 is anisotropically etched using a solution such as KOH to form the membrane 2. Then, the support frame 4 made of glass or the like having a thickness of about 5 mm is bonded to the outer peripheral surface of the back surface of the silicon substrate 3 with epoxy resin (see Fig. 3C). Finally, a resist is applied on the TaGeRe film and processed into a predetermined pattern, and the TaGeRe film is processed by dry etching using an etching gas such as SF ₆ or Cl ₂ as a resist as a mask. The X-ray absorber 1 is patterned (see FIG. 3D). According to the above process, the X-ray mask which uses a TaGeRe film as an X-ray absorber is completed. The composition ratio and film formation conditions of the TaGeRe film in this embodiment are the same as in the first embodiment.

According to the manufacturing method of the X-ray mask employed in this embodiment, unlike the first embodiment, since the X-ray absorber is formed on the silicon substrate, the stress of the X-ray absorber can be more accurately measured in each step. There is an advantage. However, when the membrane is formed by back-etching the silicon substrate after the film formation of the X-ray absorber, the support frame may be separated from the tensile stress of the membrane, and the stress between the membrane and the X-ray absorber may change. In this case, the X-ray mask can be precisely formed by forming a film with a tensile stress rather than a stress previously targeted by the X-ray absorber, or by correcting pattern data by predicting the pattern displacement amount from the stress after film formation. It is possible to do it.

Embodiment 2

The TaGeRe alloy film of the present invention can be subjected to annealing treatment after forming a film to adjust the stress in the film. In this embodiment, after forming a TaGeRe film as an X-ray absorber, an example of adjusting stress by annealing and forming an X-ray mask of low stress will be described. The film formation itself of the TaGeRe film can be performed in the same manner as in the first embodiment.

FIG. 5 is a diagram showing a relationship between a change in stress, annealing temperature and annealing time when the TaGeRe film is annealed in vacuo. As can be seen from Fig. 5, by performing annealing at a temperature of about 300 DEG C or more, the film stress is changed to the tension side immediately after the film formation. The degree of this change increases with an increase in the annealing temperature. In addition, the stress change due to annealing is saturated in about 5 to 15 minutes. The same results can be obtained by changing the annealing atmosphere to inert gas atmospheres such as Ar, Xe, and N ₂ in a vacuum.

By using this phenomenon, when the film is formed, the compressive stress film is formed in the low gas pressure region where the dependence of the stress on the sputter gas pressure is small (the slope of the graph in FIG. 4 is small) and the film can be formed with good reproducibility. After that, annealing is performed at an appropriate temperature and the stress is changed to the tensile side, whereby a low stress TaGeRe film having high reproducibility can be formed.

In addition, when the TaGeRe film is annealed in this way and the stress change is saturated, the stress changes even when the temperature of the mask rises during the resist process, etching process or exposure in the X-ray mask manufacturing process. X-ray mask with no stress and higher stability of stress can be obtained. In the usual manufacturing process, the temperature of the X-ray mask stays at about 150 ° C. or lower even if it rises. However, by annealing at a temperature higher than this in advance, the thermal margin becomes large and advantageous.

As described above, by annealing the TaGeRe film, it becomes possible to adjust the stress and improve the thermal stability in the process. From this point of view, the annealing treatment is preferably performed immediately after the film formation of the TaGeRe film. However, in the case where only the stress is adjusted, the annealing treatment may be performed after the patterning step or the like.

Example 3

In this embodiment, as in the first embodiment, an X-ray mask was manufactured using a process of forming an X-ray absorber after back etching a silicon substrate as shown in Figs. 2A to 2D. Hereinafter, the manufacturing process will be briefly described with reference to FIGS. 2A to 2D.

The steps up to the back etching of the silicon substrate 3 are carried out in exactly the same manner as in the first embodiment (see Figs. 2A to 2D). Next, as the X-ray absorber 1, a TaGeRe film is formed by the sputtering method. The composition ratio of the TaGeRe film formed here was set to Ta: Ge: Re = 1: 0.24: 0.75 (Ta = 50.2%, Ge = 12.1%, Re = 37.7%). The sputter gas pressure at the time of film formation was 0.6 Pa, which is the same as in the first embodiment. At this time, the composition ratio of the TaGeRe film formed in this embodiment is slightly smaller in Re composition than in the first embodiment. This results in a compressive stress of about 80 MPa across the membrane.

Next, annealing of the TaGeRe film is performed. Annealing conditions were 400 degreeC and 10 minutes in vacuum. By this annealing treatment, the stress of the film changes on the tension side by about 80 MPa. As a result, the stress change due to the compressive stress immediately after film formation and the annealing cancel out, and a low stress TaGeRe film whose stress is close to zero is formed.

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

Example 4

In the process of performing back etching of the silicon substrate after forming the same X-ray absorber as in the second embodiment, it is also possible to perform annealing treatment after the TaGeRe film is formed as follows.

First, SiN, SiC, etc., which form the membrane 2, are formed on both surfaces of the silicon substrate 3. Thereafter, a TaGeRe film is formed as the X-ray absorber 1 by the sputtering method, and then annealing treatment is performed. The subsequent steps are carried out in exactly the same manner as in the second embodiment to complete the X-ray mask.

Also in this embodiment, in the same manner as in the third embodiment, a TaGeRe film is formed so as to have a compressive stress at the time of film formation. For example, by forming a TaGeRe film having a composition ratio of Ta: Ge: Re = 1: 0.24: 0.75 at a sputter gas pressure of 0.6 Pa, an X-ray absorber 1 having a compressive stress of about 80 Mpa is obtained immediately after film formation. Lose. On the other hand, for example, by performing annealing at 400 ° C. for 10 minutes in a vacuum, the film stress is changed to the tensile side, whereby an extremely low stress X-ray absorber can be obtained.

As described above, as described in the first and second embodiments, the TaGeRe alloy of the present invention has very controllability by controlling its composition ratio, film formation conditions (sputter gas pressure), and conditions of annealing treatment after film formation. A good low stress thin film can be obtained. Further, by applying this to the X-ray absorber, an X-ray mask having very little positional deviation 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. It is also possible to replace other members of the X-ray mask, that is, the membrane 2, the silicon substrate 3, the support frame 4, or the like with an equivalent one.

Third embodiment

By performing X-ray lithography using an X-ray mask having a TaGeRe film as the X-ray absorber described in the first and second embodiments, a semiconductor device having a fine pattern can be manufactured with good reproducibility.

Semiconductor devices (semiconductor chips such as memories and logic, or liquid crystal panels, CCDs, thin film magnetic heads, micromachines, etc.) are commercialized through a preprocess of forming actual circuits on a wafer and a postprocess of chipping and packaging the wafer. do. Among these processes, the wafer process includes various processes such as insulating film formation, electrode formation, and ion implantation, but in each process, a process of forming a pattern according to the device design drawing on a substrate is lithography. In the lithography process, resist coating, 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, but particularly when forming a fine device pattern of about 0.13 µm or less The effect is high when forming a pattern with a large ratio (> 5 or so).

In the semiconductor device, the pattern formed in the previous layer overlaps the pattern of the next layer, but the precision is required to be equal to or less than one minute of the minimum pattern line width. Here, since the X-ray masks disclosed in the first and second embodiments (Examples 1 to 4) are highly controlled in the stress of the X-ray absorber, the positional deviation is extremely lower than that of the conventional X-ray mask. small. For example, when SiC is used in the X-ray transmissive film, the maximum positional deviation by the X-ray absorber when forming an X-ray absorber pattern of ± 5 MPa at 50% coverage in a 35 mm angle region is 5 nm or less. . Therefore, when the X-ray mask of the present invention is used in the exposure process, a faithful pattern can be manufactured with respect to the device design drawing.

According to the above, by performing the X-ray lithography using the X-ray mask using the TaGeRe alloy of the present invention, the productivity of the semiconductor device having good characteristics can be improved.

In addition, in the embodiment of the present invention, an example in which the TaGeRe alloy thin film of the present invention is applied to the X-ray absorber of the X-ray mask is described. However, the use of the TaGeRe alloy thin film is not limited to the X-ray mask. In other words, it is needless to say that the TaGeRe alloy thin film of the present invention is useful in applications where low stress characteristics are required.

The TaGeRe alloy of the present invention has a higher X-ray blocking function than conventional X-ray absorber materials. In addition, 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 at the time of film formation, a low stress film with very good reproducibility can be obtained. By these characteristics, the TaGeRe alloy thin film of the present invention is very effective as an X-ray absorber in an X-ray mask.

In addition, the stress of the TaGeRe film is hardly affected by parameters other than the sputter gas pressure. For this reason, the TaGeRe film of the present invention has a feature that a low stress film with good reproducibility can be formed even with an inexpensive film forming apparatus.

Moreover, the stress of the TaGeRe film of the present invention can be controlled by the annealing treatment after film formation. As a result, the reproducibility of the 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, it is possible to manufacture a semiconductor device having a pattern of about 0.1 µm or less with high efficiency.

Claims (12)

Alloys containing at least Ta, Ge, and Re. The method of claim 1. An alloy with a composition ratio of at least 95 atomic percent combining Ta, Ge, and Re. The alloy of claim 1 consisting of only Ta, Re and Ge. The alloy according to claim 1, wherein the Ge composition ratio is in the range of 1 to 30 atomic% and the Re composition ratio is in the range of 3 to 60 atomic%. The alloy of claim 1 having an amorphous structure. The alloy of claim 1, wherein the shape is thin film. An X-ray mask having an X-ray mask having an X-ray absorber selectively formed on an X-ray transmissive film formed of the alloy according to claim 1. A thin film made of the alloy according to claim 1 is formed on a substrate by a sputtering method using a target containing Ta, Ge, and Re. A method for producing an X-ray mask, comprising: forming a thin film made of the alloy according to claim 1 on a X-ray transparent film by a sputtering method using a target containing Ta, Ge, and Re. The method of manufacturing an X-ray mask according to claim 9, further comprising annealing the thin film after forming the thin film. A method of manufacturing a semiconductor device, comprising: 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. . A semiconductor device in which at least one layer pattern is formed by an X-ray exposure process 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.