KR100310048B1 - Improved alloy and method of preparing the same as well as X-ray mask and method of formimg 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 high X-ray bottom intelligence, 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, a high-precision X-ray mask with low positional deviation can be easily obtained to obtain an X-ray absorber material having high X-ray low intelligence, amorphous structure, and low stress characteristics with high reproducibility. do.

Description

Alloy, method for preparing X-ray mask, method for manufacturing semiconductor device, and method for manufacturing the same the 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 manufacture of LSIs 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 installed on an X-ray permeable membrane (hereinafter referred to as a 'membrane') and supported by a support frame such as a silicon substrate and glass. It is common to have one.

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, using an adhesive such as an epoxy resin, a support frame 4 such as 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 (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 substrate of the silicon substrate is formed before the formation and the patterning of the X-ray absorber, but the reverse of this order is the back of the silicon substrate after the formation of the X-ray absorber. It is also possible to 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 high X-ray low intelligence (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 ability against X-rays in the vicinity of the wavelength of 1 nm which is usually used for X-ray lithography. If the X-ray hypothesis is small, the thickness of the X-ray absorber film formed on the membrane must be thickened, and in this case, fine patterning of the X-ray absorber becomes very difficult. Moreover, when the film thickness of an X-ray absorber becomes large, a problem will arise that the pattern will become more blurred at the time of exposure, and control of stress will become difficult.

Second, it is required that the stress is as small as possible and at the same time high in controllability and stability. When a film serving as an X-ray absorber is formed on a membrane, if its internal stress is large, its positional accuracy deteriorates during patterning, and furthermore, a shift 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. Moreover, 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 desired 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 X-ray absorbers that have been used in the past.

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 forming 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. 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 support frame portion and the membrane portion, or strictly controlling the temperature of the entire vacuum chamber of the film forming apparatus are necessary. In addition, special research was needed 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 mainly the problem of crystal structure among these problems with W and Ta, many material proposals have been made so far.

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 for use as an X-ray absorber of a sun mask Since these Ta ₄ B and WTiN have an amorphous structure, the problem of roughening the pattern side wall surface resulting from the above-mentioned polycrystalline structure is solved.

However, in these alloys, B, Ti, and N contained in Ta or W are elements having low X-ray low intelligence. 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 Laid-Open No. 63-146546). However, in the case of alloys of Ta, Al, Ti, and Si, there is a problem that the X-ray low intelligence is low. Further, 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 high X-ray hypothesis and having 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 Al, Ti, Si, and the like, it is also advantageous in terms of X-ray absorption ability 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 is close to 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 is a novel that satisfies all the conditions required for the X-ray absorber, that is, having a high X-ray absorption capacity, capable of forming a low stress film with good reproducibility, a dense crystal structure, etc. An alloy material and its manufacturing method are provided. An object of the present invention is to disclose 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 precision.

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

2A to 2D are diagrams illustrating the manufacturing process of the first and third embodiments of the present invention.

3A to 3D illustrate the manufacturing 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.

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, it is preferable that the composition ratio of Ta, Ge, and Re combined is 95 atomic% or more, or only Ta, Re, and Ge. In addition, 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 to 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, you may have the process of annealing the 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.

Hereinafter, embodiments of the present invention will be described in detail with reference to the 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 of 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 desired pattern is provided.

In addition, as a manufacturing process of the X-ray mask of this embodiment, a method of performing back-etching of a silicon substrate described as a prior art before forming an X-ray absorber and a method of performing back-etching of a silicon substrate after forming an X-ray absorber Anything is possible.

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

In this embodiment, the film formation of the TaGeRe alloy was performed by the sputtering method. As the sputtering apparatus, an ordinary RF sputtering apparatus which discharges the sputtering 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 this 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 does not require any special research for controlling stress, that is, to make the vacuum chamber ultra-high vacuum, to control the temperature of the chamber 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 replace with other gases, such as Ar. However, compared with the case of using Ar as the sputter gas and the case of using Xe, the amount of gas received in the film decreases because the Xe has a large atomic radius, and thus the stress control, stability, density, etc. of the X-ray absorber are reduced. This good film can be obtained.

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 A mosaic-shaped target etc. which combines two kinds of elements remaining 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 wide 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 atomic ratio or atomic% 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, the 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, l: 0.24: 0.75, and 1: 0.24: 0.12, respectively. At the time of formation of these TaGeRe films, the substrate temperature is room temperature and the film thickness is 0.5 mu m. Incidentally, for reference, the stress of the Ta group 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 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 is obtained (that is, the slope of the graph is small). Therefore, 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 nonuniformity of the in-plane distribution of the stress caused by the variation of the gas pressure is also small. 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 low intelligence of the TaGeRe alloy is larger than that of a metal or alloy conventionally used as an X-ray absorber, and a contrast equal to a film thickness thinner than that of a conventional material can be obtained. Therefore, workability and stress controllability at the time of patterning are improved, and the overall stress of the film is also 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. Moreover, 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 that of the conventional passivation films such as Ta 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 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 practical 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 etc. which become the membrane 2 are 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). Then, the X-ray absorber 1 which consists of a TaGeRe film | membrane is formed on the membrane 2 by sputtering method (refer FIG. 2C). Thereafter, the X-ray absorber is patterned by dry etching to complete an X-ray mask having a desired pattern.

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 in which a back-etch process of a silicon substrate is performed after forming an X-ray absorber on a membrane. . 3A to 3D, the X-ray mask manufacturing process in this 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 as a X-ray absorber 1 on the SiN or SiC film on the surface of the silicon substrate 3 by the sputtering method (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 with the resist as a mask. The X-ray absorber 1 is patterned (see FIG. 3D). Through the above steps, an X-ray mask using 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, distortion may occur in the support frame due to the tensile stress of the membrane film, and the stress of 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 targeted for the X-ray absorber, or by correcting the pattern data by predicting the pattern displacement amount from the stress after film formation. It is possible to do

2nd Embodiment

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 the present embodiment, after the TaGeRe film is formed as the X-ray absorber, an example in which stress is adjusted by annealing to form a low stress X-ray mask 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 the relationship between the change in stress and the annealing temperature and the 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. Even if the atmosphere of the annealing is changed to an inert gas atmosphere such as Ar, Xe and N ₂ in vacuum, the same result can be obtained.

By using this phenomenon, in forming the film, 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 to change the stress toward 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. And an X-ray mask with higher stress stability 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. In this regard, 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 the 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 process of back etching the silicon substrate 3 is carried out in exactly the same manner as in the first embodiment (see Figs. 2A to 2D). Subsequently, a TaGeRe film is formed as the X-ray absorber 1 by the sputtering method. Here, the composition ratio of the TaGeRe film formed was made into 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, the TaGeRe film is annealed. 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 the film formation and the annealing are canceled, so that a TaGeRe film having a low stress 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 forming the TaGeRe film 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 performed in 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 DEG 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 with very little positional shift 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 of course 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 equivalents.

Third embodiment

By performing X-ray lithography using an X-ray mask having a TaGeRe film as the X-ray absorbers described in the first and second embodiments, a semiconductor device having a fine pattern can be produced 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, the X-ray masks disclosed in the first and second embodiments (the first to fourth embodiments) are extremely out of position compared to the conventional X-ray masks because the stress of the X-ray absorber is highly controlled. 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 X-ray lithography using the X-ray mask using the TaGeRe alloy of this invention, the productivity of the semiconductor device which has favorable characteristics can be improved.

In addition, in the embodiments 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 in which low stress characteristics are required.

The TaGeRe alloy of the present invention has a higher X-ray low intelligence than the conventional X-ray absorber material. 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 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 (9)

It contains at least Ta, Ge, and Re, and the composition ratio of Ta, Ge, and Re is 95 atomic% or more, and the Ge composition ratio is 1-30 atomic%, and the Re composition ratio is 3 ~ 30% of the total composition ratio by Ta, Ge, and Re. Alloy with an amorphous structure in the range of 60 atomic%. The alloy of claim 1 consisting of only Ta, Re and Ge. The alloy of claim 1, wherein the shape is thin film. An X-ray mask having an X-ray absorber selectively formed on an X-ray permeable membrane, the X-ray mask comprising an X-ray absorber formed of the alloy according to claim 1. A method for producing an alloy, wherein 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 of manufacturing 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. An X-ray exposure process of transferring an X-ray absorber pattern to a resist on a substrate by irradiating X-rays through an X-ray mask according to claim 7. A semiconductor device comprising at least one layer 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 an X-ray mask according to claim 7.