JP3306974B2 - Method for forming fine structure and X-ray mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a fine structure, and more particularly to an improvement in a method for forming a fine structure such as a LIGA method, and an improvement in a method for forming a fine structure by applying a patterning technique in a semiconductor process or the like. And an X-ray mask.

[0002]

2. Description of the Related Art In recent years, research on a fine processing technique for forming an extremely fine structure by applying a manufacturing technique of a semiconductor integrated circuit device has been actively conducted. In particular, LIGA (Lithograph) for forming a fine structure having a high aspect ratio
Galvanformmund Abformun
g) method is of particular interest (Nikkei
Mechanical 1990.11.26, p.
72-p. 79 and Mechanical Design Issue No. 6 (199
May, 1), p. 25 to p. 28). The LIGA method can be used for manufacturing a micromachine, an optical element, a sensor, an actuator, or the like, and its application range is very wide.

In the conventional LIGA method, a resist material based on polymethyl methacrylate (PMMA) is mainly used in a step of forming a resist pattern by lithography using X-rays.

Further, the present applicant discloses an invention using a chemically amplified resist in a step of forming a resist pattern using lithography by synchrotron radiation used in a step of forming a fine structure. (See Japanese Patent Application No. 3-325599).

FIGS. 6 and 7 are process charts for schematically explaining basic steps of the conventional LIGA method.

Referring to FIGS. 6 and 7, in FIG. 6 (a), typically, polymethyl methacrylate (PM
A resist layer 102 made of MA) is formed on the substrate 101 at a desired thickness (several tens μm to several hundreds μm).
Next, the resist layer 102 is exposed to synchrotron radiation (SOR light) using the X-ray mask 100 on which a desired pattern is formed. In FIG. 6B, the resist layer 102 exposed in the step of FIG. 6A is developed to form a resist pattern 103. In FIG. 6C,
The substrate 101 having the resist pattern 103 is immersed in a plating solution, and is electroplated on the substrate 101 by, for example, N2.
i, Cu, Au, and the like are deposited in the valleys of the resist pattern 103 or the like to form a metal structure 104. FIG. 6 (d)
Then, the resist material is removed to obtain a metal structure 104. Then, using the metal structure 104 as a mold, a dielectric plastic is injected into the metal structure 10 by an injection molding method.
4 to form a dielectric plastic molding material 105. Next, in FIG. 7A, according to the mold material 105 made of the dielectric plastic material manufactured in the step of FIG.
08 is formed. Next, in FIG. 7B, the mold material 105 is separated, and a plastic mold 108 is prepared. Next, in FIG.
The metal 109 is deposited by electroforming between the valleys. Next, in FIG. 7D, the plastic mold 108 is removed, and a fine metal structure 110 is obtained.

In recent years, the degree of integration of semiconductor integrated circuits has been increasing year by year, and VLSI (very large scale I) has been developed.
In the field of manufacturing semiconductor integrated circuits and the like, the necessity of miniaturizing the element structure of semiconductor elements has been increasing in accordance with the increase in integration of integrated circuits. Instead of the photolithography method using (wavelength of about 3000 to 5000), an X-ray (wavelength of about 10) lithography method using light having a shorter wavelength has attracted attention.

FIG. 8 is a sectional view schematically showing an X-ray mask used for X-ray lithography at the time of patterning such a conventional semiconductor integrated circuit or the like. Referring to FIG. 8, X-ray mask 200 has an opening 201 at the center.
h and a silicon substrate 201
An X-ray permeable film (membrane) 202 provided so as to cover the surface 201a on one side thereof, and an X-ray absorber film 203 having a desired pattern formed on the surface of the X-ray permeable film 202. The X-ray permeable film 202 is made of a material that transmits X-rays, that is, a material having a high X-ray transmittance, such as silicon nitride (Si).
N) and silicon carbide (SiC).

On the other hand, the X-ray absorber film 203 is made of a material that easily absorbs X-rays, that is, a material having a low X-ray transmittance, such as tungsten (W) or tantalum (Ta). Then, the X-ray absorber film 203 is supported by the X-ray transmission film 202.
On the other surface 201b of the silicon substrate 201, a film 204 made of, for example, silicon nitride (SiN) or silicon carbide (SiC) is provided. The average thickness of the X-ray absorber film 203 of the conventional photomask is about 0.7 μm.

Next, a conventional method for manufacturing a photomask will be described below. 9 and 10 show a conventional X.
FIG. 4 is a process chart schematically showing a step of manufacturing a line mask.
Referring to FIGS. 9 and 10, first, in FIG. 9A, a chemical vapor deposition (CVD) method is used.
or Deposition method) or physical vapor method (PVD (Physical Vapor Depos)).
An X-ray permeable film 202 made of silicon nitride (SiN) or silicon carbide (SiC) having a thickness of about 2 μm is formed on one surface 201a of the silicon substrate 201 by an ition method). In this step, a film 2 made of silicon nitride (SiN) or silicon carbide (SiC) serving as an etching mask when back-etching the silicon substrate 201 described in a later step.
04 is formed in a predetermined region on the other surface 201b of the silicon substrate 201 by a chemical vapor method or a physical vapor method. Next, in FIG. 9B, an X-ray absorber film layer 203a made of tungsten (W) or tantalum (Ta) is formed on the surface of the X-ray transmission film 202.
Is formed by a chemical vapor method or a physical vapor method. The film thickness of the X-ray absorber film layer 203a is about 0.7 μm. Next, in FIG. 9C, a resist layer 205 is formed on the surface of the X-ray absorber film layer 203a by spin coating using a resist material.

In the following, the resist material is applied to the X-ray absorber film layer 2
A method of applying a spin coat method on the surface of No. 03a will be illustratively described. First, resist material,
After a certain amount is dropped from the nozzle onto the surface of the X-ray absorber film layer 203a, the resist material is spread on the surface of the X-ray absorber film layer 203a by being left for a while. Next, by using a spinner or the like to rapidly rotate the silicon substrate 201 at a high speed, excess resist is scattered to form a resist layer 205 having a uniform film thickness. In this manner, the thickness of the resist layer 205 formed on the surface of the X-ray absorber film layer 203a varies depending on the viscosity of the resist to be applied, the number of rotations of the spinner, and the evaporation speed of the solvent. It is as follows.

Next, in FIG. 9D, an electron beam device (EB device) (not shown) is used to
6, the resist layer 2 is formed into a desired mask absorber shape.
05 is drawn (exposed). In the step shown in FIG. 9D, for example, when a resist material for photolithography is used, the resist layer 205 is exposed to ultraviolet rays (wavelength: about 3000 to 5000) to form a desired mask absorber. Sometimes.

Next, in FIG. 10A, a desired resist pattern 205a is formed by developing the exposed resist layer 205. Next, referring to FIG. 10B, using the resist pattern 205a as a mask, the X-ray absorber film layer 203a exposed through the opening 205b is subjected to reactive ion etching (PET) so as to penetrate the X-ray absorber film layer 203a. RIE (React
(Even Ion Etching)) method. Next, FIG.
(C), after removing the resist layer, using the film 204 as an etching mask, a reactive ion etching method,
By dry etching, wet etching, etc.
The X-ray mask 200 is formed by etching (back etching) the silicon substrate 201 from the other surface 201b of the silicon substrate 201 to the X-ray permeable film 202 (see FIG. 10D).

Referring again to FIG. 9D, the resist layer 205 is formed in a desired direction in the thickness direction (depth direction) of the resist layer 205 by using the electron beam line 206 and ultraviolet rays (wavelength: 3000 to 5000). The depth at which the shape can be exposed with high precision is about 2 μm. This may be due to electron beam radiation of the resist material, ultraviolet light (wavelength 3000 to 50).
00Å), and a decrease in the accuracy of the resist pattern due to the diffraction effect of light.

Referring again to FIG. 10B, in the step of etching the X-ray absorber film layer 203a using the resist pattern 205a as a mask, the X-ray absorber film layer 203a is replaced with the X-ray absorber film layer 203.
In order to etch to a film thickness in the thickness direction (depth direction) of a, it is necessary to increase the selectivity represented by the following equation (1).

[0016]

(Equation 1)

However, even if various etching gases (reaction gases) or the like are used, there is a limit in increasing the selectivity.

As described above, in the conventional X-ray mask, it is difficult to form a thick resist layer in the mask forming process, and a high-precision deep exposure in the depth direction of the resist layer is required. Difficulty, difficulty in forming a high-precision deep resist pattern in the depth direction of the resist layer, and increasing the selectivity of the etching rate of the resist layer and the etching rate of the X-ray absorber film layer In the field of semiconductor device manufacturing, the lithography exposure process usually has
When light having a wavelength of about 0 ° to 4000 ° is used, when the film thickness of the X-ray absorber is increased, the diffraction effect of light causes
From the problem that the resolution of the pattern transferred to the resist layer is reduced, the thickness of the absorber of the photomask is
Usually, an X-ray mask having a thickness of about 0.7 μm is used. Further, the conventional X shown in FIGS.
In the method for manufacturing a line mask, the film thickness of the X-ray absorber that can be patterned is up to about 3 μm even when the selectivity shown in the equation (1) is increased.

In lithography used in a semiconductor manufacturing process, a copolymer resist composed of methyl methacrylate (MMA) and methacrylic acid (MAA) is known (J. Electrochem., So.
c. , Vol126, No. 1 (1979), p. Fifteen
4-p. 161).

The step of forming a resist layer on a lithographic semiconductor substrate used in a semiconductor manufacturing process includes:
Usually, a spin coating method is used.

Hereinafter, a method for applying a copolymer resist composed of methyl methacrylate and methacrylic acid on a semiconductor substrate will be described by way of example.

In lithography used in a semiconductor manufacturing process, a copolymer resist composed of methyl methacrylate and methacrylic acid is prepared by polymerizing a methyl methacrylate monomer and a methacrylic acid monomer in a solvent such as toluene. A copolymer of methyl methacrylate and methacrylic acid prepared in a solvent such as toluene is precipitated with methanol or the like. The copolymer composed of methyl methacrylate and methacrylic acid is purified and then dissolved in a solvent such as ethyl cellosolve acetate (ECA). Next, a solution in which a copolymer composed of methyl methacrylate and methacrylic acid is dissolved is dropped on a semiconductor substrate, and is uniformly applied to a predetermined thickness on the semiconductor substrate by a spin coating method. Next, by heat-treating a semiconductor substrate having a solution layer in which a copolymer of methyl methacrylate and methacrylic acid is dissolved, and removing the solvent, a copolymer of methyl methacrylate and methacrylic acid is formed on the semiconductor substrate. A resist layer is formed. The thickness of the resist layer formed on the semiconductor substrate thus obtained is 3 μm or less.

[0023]

However, the above-described LI
In the field of forming microstructures using the GA method, etc., PM
Due to the low X-ray absorption of the MA-based resist,
There is a problem that long-time exposure must be performed using a large-sized and high-performance synchrotron radiation device having high light intensity. Further, in order to obtain a high-resolution resist pattern, it is necessary to reduce the light diffraction effect. In order to perform a deeper exposure (about several tens μm or more) in the vertical direction, a short wavelength (about 2 to 5 °) is required. ) Synchrotron radiation had to be used. FIG. 11 shows the correlation between the thickness (depth) of a resist that can be patterned in the thickness direction (depth direction) of a resist layer using generally used polymethyl methacrylate (PMMA) and the wavelength of X-rays. FIG. Referring to FIG. 11, theoretically, by using a light having a short wavelength, the diffraction effect of light can be reduced by forming the resist layer thickly, and the resist layer can be formed in a thickness direction (depth direction). Direction) deep patterning can be performed with high precision.

Therefore, especially in the field of the LIGA method, in order to form a fine structure having a high aspect ratio, synchrotron radiation having a short wavelength (about 2 ° to 5 °) is applied for a long time at a high light source intensity. A synchrotron radiation device capable of irradiation has been desired.

However, it is generally difficult to use such a synchrotron radiation device.

An object of the first invention is to provide a synchrotron radiation device which can be generally used easily,
An object of the present invention is to provide a method capable of implementing the IGA method or the like.

Another object of the first invention is to provide a lithography using synchrotron radiation with a short exposure time.
It is an object of the present invention to provide a method for forming a deep resist pattern in a vertical direction and thereby forming a fine structure having a high aspect ratio.

It is a further object of the first invention to perform lithography with a higher resolution by using synchrotron radiation having a longer wavelength, to form a deep resist pattern in the vertical direction, thereby achieving an aspect ratio. To provide a method for forming a fine structure having a high density.

In the case of a micromachine, an optical element, a sensor, an actuator, or the like, it is necessary to form a metal structure having a large aspect ratio (length / width) on the order of μm from the viewpoint of securing mechanical strength. . The thickness of such a microstructure varies depending on the application and purpose of the microstructure, but usually varies from about 1 μm to about 1 mm. For this reason, when a microstructure such as a micromachine is formed by using the LIGA method or the like,
Referring to FIG. 6A, the thickness of resist layer 102 (several tens μm to several tens
It is necessary to form a deep resist pattern in the thickness direction (depth direction) of the resist layer 102. For this reason, when a microstructure is formed by the LIGA method or the like, a short wavelength (2 to 1) is used in order to reduce the diffraction effect of light and expose the resist layer deeply in the thickness direction (depth direction).
Synchrotron radiation of about 5 °) is applied to an X-ray mask 10
Over 0, it was necessary to expose for a long time.

FIG. 12 is a correlation diagram showing the correlation between the film thickness of an X-ray absorber required as an X-ray mask used in manufacturing a micromachine or the like using the LIGA method or the like and the wavelength of X-rays. It is. Referring to FIG.
When manufacturing a micromachine or the like using the method A or the like,
The average film thickness of the X-ray absorber of the X-ray mask is required to be 5 μm or more. That is, in the conventional X-ray mask used for manufacturing a semiconductor integrated circuit or the like, the average film thickness of the X-ray absorber is about 0.7 μm.
Referring to (a), when the synchrotron radiation is irradiated on the resist layer 102 through the X-ray mask 100 for a long time, the synchrotron radiation passes through the X-ray absorber film 100a. In addition, there is a problem that a portion not requiring exposure is exposed, and a desired resist pattern cannot be obtained.

When a micromachine or the like is manufactured by using the LIGA method or the like, an X-ray absorber film having an X-ray absorber film that can sufficiently shield the synchrotron radiation even when irradiated with the synchrotron radiation for a long time. A line mask, that is, an X-ray mask having an average film thickness of 5 μm or more as an X-ray absorber film has been desired for many years. on the other hand,
As described above, the average film thickness of the X-ray absorber film that can be formed by the conventional X-ray mask manufacturing method is about 0.7 μm, and the average film thickness of the X-ray absorber film in the conventional X-ray mask manufacturing method is X having a film thickness of 3 μm or more
It was difficult to manufacture a line mask.

The second object of the present invention is to solve the problems of the conventional method of manufacturing an X-ray mask, in particular, to make the X-ray absorber film thicker (5 μm or more) than in the prior art. It is an object of the present invention to provide a method capable of easily forming a thick microstructure by a lithography step and an etching step such that the microstructure can be formed.

[0033]

The following characteristics are required for a resist material used for lithography used in the process of forming a fine structure.

High sensitivity. -High resolution.

The resist layer can be formed thicker in the vertical direction than the substrate or the like. When the resist layer is formed thick, deep exposure can be performed perpendicularly to the depth direction of the resist layer, and a resist pattern having a high aspect ratio can be formed.

The present inventors have been enthusiastically studying a method for forming a fine structure having a high aspect ratio for many years, and have found that methyl methacrylate and methacrylic acid used in lithography in a semiconductor manufacturing process are used. When a polymer resist is used as a resist material, P
Paying attention to higher sensitivity than MMA, it has been found that a copolymer composed of methyl methacrylate and methacrylic acid is suitable as a resist material used in lithography in a method for forming a fine structure. Reached.

[0037]

[0038]

[0039]

[0040]

[0041]

Method for forming a fine structure according to the first invention
Forming a resist layer on a substrate;
Lithography using synchrotron radiation
Forming a distaste pattern
In the method of forming, the resist layer has a general formula

[0043]

Embedded image

A monomer represented by the formula: wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (a hydrogen atom of the alkyl group may be substituted by a halogen atom);

[0045]

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Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group, to prepare a copolymer syrup comprising the following: The method includes a step of applying a copolymer syrup on a substrate, and a polymerization completion step of completely polymerizing the copolymer syrup layer formed on the substrate in the application step on the substrate.

Further, the method for forming a microstructure according to the second invention comprises a step of forming a resist layer on a solid surface;
A step of forming a resist pattern having an opening on the resist layer using lithography by synchrotron radiation, and a step of etching and removing a solid portion exposed through the opening using the resist pattern as a mask; In the method of forming a structure, the step of forming a resist layer on a solid surface is performed by a general formula

[0048]

Embedded image

Wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (a hydrogen atom of the alkyl group may be substituted with a halogen atom);

[0050]

Embedded image

Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group, and a monomer represented by the following formula is preliminarily polymerized to prepare a copolymer syrup comprising them: The method includes a step of applying a copolymer syrup on a solid surface, and a polymerization completion step of completely polymerizing the copolymer syrup layer formed on the solid surface by the coating step on the solid surface.

Manufacturing of X-ray mask according to the third invention
The method forms a resist layer on the surface of the X-ray absorber film
Forming a resist pattern on the resist layer.
Removing the resist pattern using the resist pattern as a mask.
Etching the gamma ray absorber film, and the resist
Removing the pattern; and
Back etching from the surface to the X-ray transparent body film
Extent, in the manufacturing method of the X-ray mask comprising the step is represented by the formula to form a (1) the resist layer
Pre-polymerized two types of monomer
Providing a copolymer syrup;
Applying a tip on the surface of the X-ray absorber film
And the surface of the X-ray absorber film by the coating step
The copolymer syrup layer formed on top is completely
And (2) the X-ray absorber film has an average film thickness of 5 μm or more.
It is characterized by the following.

The copolymer resist used in the present invention can be exemplarily represented by the following general formula.

[0054]

Embedded image

Wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (a hydrogen atom of the alkyl group may be substituted by a halogen atom), X is a halogen atom or a hydroxyl group,
R ₂ is a hydrogen atom or a methyl group.] As the methacrylic acid ester (monomer) used in the present invention, various raw material monomers for a resist material used for lithography in a semiconductor manufacturing process can be used. Methacrylic acid ester (monomer) used in the present invention
Is represented by the following general formula.

[0056]

Embedded image

[In the formula, R ₁ is an alkyl group having 1 to 4 carbon atoms (the hydrogen atom of the alkyl group may be substituted with a halogen atom)] In the formula, R ₁ is an n-alkyl group, It includes a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group.

Specific examples of the methacrylate used in the present invention include, for example, methyl methacrylate, 2-fluoroethyl methacrylate, 2,2,2
-Trifluoroethyl methacrylate, tetrafluoroisopropyl methacrylate, hexafluorobutyl methacrylate, 2-chloroethyl methacrylate, 2-
Bromoethyl methacrylate (solid state technology / Japan version / February 1990, p.28-p.3).
5).

As the monomer to be copolymerized with the methacrylic acid ester of the copolymer resist used in the present invention, various monomers represented by the following general formula can be used.

[0060]

Embedded image

Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group. Specific examples of such a monomer include, for example, methacrylic acid, methacryloyl halogenide, acrylic acid, And acryloyl halogenide.

As used herein, the term “preliminary polymerization”
This means that a certain amount of the charged monomer is polymerized so that a part of the charged monomer and the produced copolymer polymer coexist.

The term “copolymer syrup” as used herein means that a part of the charged monomers and the formed copolymer polymer are present in a coexisting state.

[0064]

The copolymer resist used in the present invention is a water-soluble substance having a carboxyl group at the terminal while the main chain of the copolymer resist is cut at the irradiated part (exposed part) of synchrotron radiation. The solubility in a developing solution such as an aqueous alkali solution such as an aqueous NaOH solution or ethyl-cellosolve-acetate (ECA), methyl-cellosolve-acetate, cyclopentane, or methyl isobutyl ketone increases, so that the compound becomes soluble in the developing solution.

In the step of forming a resist pattern on a resist by lithography using synchrotron radiation, the exposure time (T) required for lithography
Is expressed by Expression (2) by the intensity (I) of the exposure radiation source and the sensitivity (S) of the resist.

T = S / I (2) Since the above-described copolymer resist according to the present invention has high reactivity of the resist, the value of the sensitivity (S) in the above formula (2) can be reduced. . By reducing the value of the sensitivity (S) in the above equation (2), the exposure time can be shortened without increasing the intensity of the exposure radiation source.

Further, the use of the above-described copolymer resist increases the sensitivity, so that even if the intensity of the exposure radiation source is weak, that is, for example, even if a long wavelength synchrotron radiation is used, Can be exposed to a deeper part.

Furthermore, the resolution of the resist is improved by reducing the light diffraction effect, that is, by using short wavelength light. However, by using the above-described copolymer resist according to the present invention, the resist resolution can be improved. It can also be improved by a chemical reaction mechanism and a development mechanism.

As shown above, according to the present invention,
By using the above-described copolymer resist, it is possible to form a resist pattern having a high aspect ratio with a smaller irradiation amount. A fine structure having a specific ratio can be obtained. By etching the substrate portion exposed through the opening of the resist pattern using the obtained resist pattern as a mask, a fine structure having a high aspect ratio having a concave portion in the depth direction of the substrate can be obtained.

According to the first and second inventions, when forming a resist layer on a substrate or a solid surface, a general formula

[0071]

Embedded image

A monomer represented by the formula: wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (the hydrogen atom of the alkyl group may be substituted by a halogen atom);

[0073]

Embedded image

Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group, and a monomer represented by the following formula: is prepared to prepare a copolymer syrup comprising Coating the copolymer syrup on the substrate or solid surface, and completely polymerizing the copolymer syrup layer formed on the substrate or solid surface by the coating process on the substrate or solid surface When the resist layer is formed by the polymerization completion step, the resist layer can be formed to have a film thickness as compared with a resist layer formed by a conventional spin coating method.

According to the second aspect of the present invention, after a resist layer is formed thick on the surface of the solid, a resist pattern having an opening is formed, and the resist pattern is masked to expose the solid exposed through the opening. By removing the portion by etching, the resist layer can be formed on the solid surface without increasing the selectivity shown by the formula (1), as compared with the case where the resist layer is formed using a conventional spin coating method. In addition, the solid can be etched deeper in the depth direction by the amount of the resist layer formed as a thick film .

In the X-ray mask according to the third invention, since the average thickness of the X-ray absorber film is 5 μm or more, the resist layer formed on the substrate using the X-ray mask according to the third invention is If a resist pattern is formed by using lithography with synchrotron radiation, even if the resist layer is irradiated with the synchrotron radiation at a constant intensity for a long time through the X-ray mask according to the third invention, the X-ray absorber film can be formed. However, since the synchrotron radiation can be sufficiently shielded, a resist pattern having a high aspect ratio can be formed with high precision. The use of the X-ray mask according to the third aspect of the present invention makes it possible to form a resist pattern having a high aspect ratio as compared with conventional lithography using an X-ray mask used for manufacturing a semiconductor integrated circuit or the like. By performing ordinary electroplating and electroforming according to the pattern, a fine structure having a high aspect ratio can be obtained.

[0077]

[Examples] Examples will be shown below.
It is only used to describe the present invention,
The present invention is not limited at all by the following examples.

Examples 1 and 2 Example 1 A methyl methacrylate monomer (molecular weight: 100)
g (0.95 mol) and 5 g (0.051 mol) of methacrylic acid (molecular weight: 86) were mixed in a mixed solution of 0.2 g of 2,2-azoisobutylnitrile as a polymerization initiator. About 0.2% by weight based on the monomer), and a bulk polymerization method was carried out under a N ₂ gas atmosphere.
Prepolymerization was performed at 0 ° C. for 50 minutes to prepare a copolymer syrup of methyl methacrylate and methacrylic acid. The weight average molecular weight of this copolymer syrup comprising methyl methacrylate and methacrylic acid was 400,000.

Example 2 A methyl methacrylate monomer (molecular weight: 100)
g (0.90 mol) and 10 g (0.116 mol) of methacrylic acid (molecular weight: 86) were mixed at a ratio of 0.2 g of 2,2-azoisobutylnitrile as a polymerization initiator. About 0.2% by weight based on the monomer), and added by bulk polymerization under N ₂ gas atmosphere.
Prepolymerization was performed at 50 ° C. for 50 minutes to prepare a copolymer syrup composed of methyl methacrylate and methacrylic acid.
The weight average molecular weight of the copolymer syrup of methyl methacrylate and methacrylic acid was 500,000.

FIG. 1 is a process diagram schematically showing an embodiment of a process of forming a copolymer resist layer composed of methyl methacrylate and methacrylic acid on a substrate.

Referring to FIG. 1, in FIG. 1A, a silicon substrate 2 is mounted on a hot plate 1 and a spacer 3 is mounted on the silicon substrate 2. Next, FIG.
, A copolymer syrup 4 composed of methyl methacrylate and methacrylic acid prepared as described above is dropped into the spacer 3 and filled. In FIG. 1C, a Kapton sheet (release sheet) 5 is placed on the spacer 3,
A metal plate 6 is placed on a Kapton sheet 5, and a weight 7 is placed on the metal plate 6.
After holding for a time, four layers of the copolymer syrup composed of methyl methacrylate and methacrylic acid were completely polymerized on the silicon substrate 2.

Through the above steps, the silicon substrate 2
A copolymer resist layer composed of methyl methacrylate and methacrylic acid could be formed in a thickness range of 50 μm to 350 μm. Various thicknesses (several tens μm to 1 mm) can be obtained by changing the thickness (height) of the spacer 3.
Can be formed.

Next, the temperature of the silicon substrate 2 having the resist layer is raised from room temperature to 200 ° C. over 1 hour, and then maintained at 200 ° C. for 3 hours. Pre-baking was performed to lower the temperature.

The prebaking is performed to remove the internal stress of the resist layer formed on the silicon substrate 2 and to improve the adhesion between the silicon substrate 2 and the resist layer. The temperature rise may be at least as high as the glass transition point (about 160 ° C.) of the copolymer composed of methyl methacrylate and methacrylic acid.
It is not limited to ° C. Further, there is no particular limitation on the time required for increasing the temperature, the time for maintaining the temperature, and the time required for decreasing the temperature. However, in order to improve the adhesion between the silicon substrate 2 and the copolymer resist composed of methyl methacrylate and methacrylic acid, the holding temperature at a high temperature needs to be sufficiently long.

In order to reduce the number of cracks, it is preferable that the time required for lowering the temperature be longer than the time required for raising the temperature. As a result, cracks are prevented by reducing the stress generated in the copolymer resist layer due to the difference in thermal expansion coefficient between the silicon substrate 2 and the copolymer composed of methyl methacrylate and methacrylic acid. can do.

Next, using a perforated mask having a desired pattern, a synchrotron radiation device (DENSO TERA
Using S), zero-order light of synchrotron radiation having a peak wavelength of about 10 ° was irradiated through a Be window.

The irradiation amount was 30 mA · accumulated beam current value.
Hours to 90 mA · hour. Next, the silicon substrate 2 having the resist layer exposed as described above was immersed in a methyl isobutyl ketone (MIBK) stock solution at room temperature for about 2 minutes while the silicon substrate 2 was stationary, and developed.

FIG. 2 shows the irradiation amount (mA · m) of synchrotron radiation for the conventional resist material (polymethyl methacrylate (PMMA)) and the resist material according to the present invention.
FIG. 7 is a diagram showing an exposing thickness (μm) with respect to time.

As is clear from FIG. 2, in the first and second embodiments, deep exposure can be performed with a smaller irradiation amount than the conventional PMMA. That is, the resist material according to the present invention has higher sensitivity than conventional PMMA, and the resist material according to the present invention can perform deep exposure even when a thick resist layer is formed on a substrate. The resist pattern formed by the development had a deep resist pattern in the vertical direction with less dripping, and had high resolution.

Note that there was no difference in sensitivity between Example 1 and Example 2. Further, the irradiation amount and the vertical depth of the resist pattern in the case of using the PMMA and the resist material according to the present invention, respectively, were compared. Table 1 shows the results
Shown in

[0091]

[Table 1]

As is clear from Table 1, when synchrotron radiation having the same accumulated current value (mA · hour) is used, according to the present invention, the exposure time for obtaining the same depth is about 1
/ 7. That is, when the resist material according to the present invention is used, a vertically deep resist pattern can be efficiently produced in a short time.

In the present embodiment, the resist layer on the substrate is compared with the method of applying a copolymer resist composed of methyl methacrylate and methacrylic acid in a semiconductor process, in which a copolymer resist composed of methyl methacrylate and methacrylic acid is used. Can be formed thick.

Further, in this example, even though the copolymer resist composed of methyl methacrylate and methacrylic acid was formed thick, a single exposure could cause the copolymer resist layer to undergo positive-negative reversal. It was possible to form a resist pattern having a height in the vertical direction by exposing it to a deeper position. That is, in the positive resist, a decomposition reaction of the polymer main chain occurs in the exposed portion,
A polymerization reaction is also caused by the generated radical. For this reason, in the positive resist, the decomposition reaction and the polymerization reaction are balanced by an increase in the amount of radicals generated by the decomposition reaction described above, or when the polymerization reaction proceeds more than the decomposition reaction,
Even if the exposure is further performed, the resist will not be dissolved in the developing solution. However, in the present embodiment, such an effect that such a positive-negative reversal is unlikely to occur is achieved, so that a deep exposure can be performed at one time.

Further, it is considered that the fact that the transmittance of X-rays is higher than that of PMMA also contributes to the fact that deep exposure is possible.

In this embodiment, several tens μm to 1 mm
Resist pattern with high sensitivity, high resolution, and high aspect ratio can be formed.
Microstructures of various materials requiring a thickness of 00 μm can be formed with a high aspect ratio, with high accuracy, and in a short time.

In this embodiment, a copolymer composed of methyl methacrylate and methacrylic acid is produced by a bulk polymerization method. Therefore, the step of removing the solvent, unlike the step of forming a resist layer on a lithographic semiconductor substrate used in a conventional semiconductor process, becomes unnecessary.

In this embodiment, the copolymer resist layer formed of methyl methacrylate and methacrylic acid formed on the substrate does not contain a solvent in the resist layer. In a step of forming a resist layer on a semiconductor substrate for lithography used in a conventional semiconductor process, the solvent may remain in the resist layer formed on the semiconductor substrate even after the solvent is removed. When the solvent is contained in the resist layer as described above, at the time of development, the solvent dissolves in the developer, the resist pattern loses its shape, and cracks occur in the resist layer. When a crack occurs in the resist layer, the mechanical strength of the resist layer decreases, and plating is performed to an unnecessary portion in the LIGA method, and a fine structure as designed cannot be obtained.

On the other hand, in this embodiment, since a copolymer composed of methyl methacrylate and methacrylic acid is prepared by the bulk polymerization method, the resist pattern loses its shape during development and cracks are formed in the resist layer. It is unlikely to occur.
The step of forming a resist layer on the substrate according to the present embodiment,
The resist layer can be formed thick on the substrate. Moreover, since the resist pattern does not easily become out of shape or crack in the resist layer during development, the formation of a fine structure including a step of forming a metal structure on a substrate by electroplating or the like according to the resist pattern is performed. In the method, the resist layer of this embodiment can be suitably used.

Example 3 According to the present invention, an X-ray permeable film made of a substance that transmits X-rays, and an X-ray absorber film formed on the surface of the X-ray permeable film, wherein the average film thickness of the X-ray absorber film is 5 μm The steps of manufacturing the photomask described above will be described below with reference to FIGS. Referring to FIGS. 3 and 4, first, FIG.
In the process shown in (1), the surface 11a on one side of the silicon substrate 11 is formed by a chemical vapor method or a physical vapor method.
An X-ray permeable film 12 made of silicon nitride (SiN) or silicon carbide (SiC) having an average thickness of about 2 μm was formed. In this step, a film 14 made of silicon nitride (SiN) or silicon carbide (SiC) or the like serving as an etching mask when back-etching the silicon substrate 11 described in a later step is formed on the other side of the silicon substrate 11. A predetermined region on the surface 11b is formed by a chemical vapor method or a physical vapor method. Note that FIG.
The step shown in FIG. 9A is the same as the conventional step shown in FIG. Next, in a step shown in FIG. 3B, an X-ray absorber film layer 13a made of tungsten (W) having an average thickness of 5 μm is formed on the surface of the X-ray permeable film 12 by a chemical vapor deposition method or a physical vapor deposition method. Formed by using In addition,
In this step, on the surface of the X-ray permeable film 12,
The X-ray absorber film layer 13a made of tungsten (W), tantalum (Ta), or the like can be formed to a desired thickness by using a chemical vapor method or a physical vapor method. In the step shown in FIG. 3B, the X-ray absorber film layer 13a has a thickness smaller than that of the conventional X-ray mask manufacturing method shown in FIG. The process is the same as the process shown in FIG.

Next, in the step shown in FIG. 3C, first, as in Example 1, 95 g (0.95 mol) of methyl methacrylate monomer (molecular weight 100) and methacrylic acid (molecular weight 86) were used. 5 g (0.051 mol) of a mixed solution mixed at a ratio of 2,2-
0.2 g of azoisobutylnitrile (about 0.2% by weight based on the above-mentioned mixed monomer) was added, and preliminarily polymerized at 60 ° C. for 50 minutes by a bulk polymerization method in an N ₂ gas atmosphere. Methyl methacrylate and methacrylic A copolymer syrup with acid was prepared. Next, in the same manner as in the step shown in FIG. 1, a copolymer resist layer 15 composed of methyl methacrylate and methacrylic acid was formed on the surface of the X-ray absorber film layer 13a with an average film thickness of 50 μm.

FIG. 5 is a process chart for explaining the process shown in FIG. 3C in more detail. Referring to FIG.
In the step shown in (a), on the hot plate 21,
An X-ray transmission film 12 and an X-ray absorber film layer 13a on the surface of the X-ray transmission film 12 are formed on one surface 11a of the silicon substrate 11, and the other surface 11b
The silicon substrate 11 on which the film 14 is formed in a predetermined region is placed, and the spacers 23 are arranged so as to surround the silicon substrate 11.
Was provided. Next, in the step shown in FIG. 5B, the copolymer syrup 24 composed of methyl methacrylate and methacrylic acid prepared above was dropped and filled in the spacer 23. Next, in the step shown in FIG.
Kapton sheet (release sheet) 25 on spacer 23
After placing the metal plate 26 on the Kapton sheet 25 and placing the weight 27 on the metal plate 26, the hot plate 21 is held at 70 ° C. for 1 hour, and the X-ray absorber film layer 13 a By completely polymerizing the copolymer syrup layer 24 composed of methyl methacrylate and methacrylic acid, a copolymer resist layer 15 composed of methyl methacrylate and methacrylic acid was formed.

Next, referring again to FIG. 3, in the step shown in FIG. 3D, the X-ray mask 30 (the average film thickness of the X-ray absorber film 33) having a desired pattern manufactured by the conventional manufacturing method is used. 33d is 0.7 μm)
Using synchrotron radiation equipment (DENSO TERA)
Using S ), zero-order light of synchrotron radiation having a peak wavelength of about 10 ° was irradiated through a Be window.

The irradiation amount was 70 mA · accumulated beam current value.
Hours to 90 mA · hour. Next, in the step shown in FIG. 4A, the silicon substrate 11 having the resist layer exposed on the surface is exposed to a methyl isobutyl ketone (MIBK) stock solution at room temperature while the silicon substrate 11 is stationary. Soaked for 2 minutes and developed. In this step, no decrease in the thickness of the resist layer was observed, and the synchrotron radiation was sufficiently shielded by the X-ray absorber film 33 in which the average thickness 33d of the X-ray mask 30 was 0.7 μm. The unnecessary portion is not exposed, and the resist pattern 15a with high accuracy and high reproducibility is provided.
Could be obtained. Next, in the step shown in FIG. 4B, using the resist pattern 15a formed in the step shown in FIG. 4A as a mask, the X-ray absorber film layer 13a exposed through the opening 15b is removed. Etching was performed by the RIE method so as to penetrate the body film layer 13a. The etching absorber film layer 13a having an average thickness of 5 μm was etched using a known RIE dry etching apparatus under the following conditions.

[0105]

[Table 2]

Under the above conditions, the X-ray absorber film 13 having a highly accurate pattern having a desired shape penetrating the X-ray absorber film layer 13a having an average film thickness of 5 μm could be formed.

Next, in the step shown in FIG. 4C, after removing the resist layer, the silicon substrate 11 is removed from the surface 11b on the other side of the silicon substrate 11 by using a KOH aqueous solution with the film 14 as an etching mask. The X-ray mask 40 according to the present invention could be formed by etching and removing (back-etching) the X-ray permeable film 12 (see FIG. 4D).

According to the third embodiment, a conventional electron beam drawing method or ultraviolet light (wavelength: about 3000 to 5000)
An X-ray mask having an X-ray absorber film with an average film thickness of 5 μm or more can be easily formed by an X-ray lithography method using synchrotron radiation and a normal etching process, without using a photolithography method using a photolithography method. .

In the third embodiment, an example was shown in which the copolymer resist layer 15 of methyl methacrylate and methacrylic acid was formed on the surface of the X-ray absorber film layer 13a with an average film thickness of 50 μm. If the average thickness of the resist layer 15 is 20 μm or more, the copolymer resist layer 1
5, X of synchrotron radiation having a wavelength of about 10 °
Resist pattern 15 having openings 15b using wires
After the formation of a, the X-ray absorber film layer 13a is etched using the resist pattern 15a as a mask, so that the average film thickness of the X-ray absorber film 13, which is impossible with the conventional method of manufacturing an X-ray mask, is obtained. An X-ray mask of 5 μm or more can be manufactured.

Referring to FIG. 4A, the resist pattern 15 formed on the X-ray absorber film layer 13a is formed.
The shape of “a” was substantially perpendicular to the surface of the X-ray absorber film layer 13a, and the dimensional accuracy was very good. Therefore, by etching the X-ray absorber film layer 13a using the resist pattern 15a as a mask,
The X-ray absorber 13 with high dimensional accuracy can be formed.

The disclosure relating to the third embodiment is merely a specific example of the present invention, and does not limit the technical scope of the present invention.

According to the second aspect, the resist layer can be formed to have a thickness and a resist pattern having openings in the thickness direction (depth direction) of the resist layer can be formed. When the solid portion exposed through the opening is etched using the pattern as a mask, a fine structure having a deep recess in the solid and a high aspect ratio can be formed.

In the first to third embodiments, only the lithography using a copolymer resist composed of methyl methacrylate and methacrylic acid has been described. However, this is used only for explanation. The present invention is not limited to a method for forming a fine structure including a lithography step using a copolymer resist composed of methyl methacrylate and methacrylic acid.

A copolymer resist of another methacrylic acid ester and methacrylic acid, a copolymer resist of another methacrylic acid ester and methacryloyl halide,
Even when using a copolymer resist of another methacrylic acid ester and acrylic acid, or a copolymer resist of another methacrylic acid ester and acryloyl halogenide, the above-mentioned methyl methacrylate and methacrylic acid A copolymer resist having a chemical reaction mechanism similar to that of the above-described copolymer resist has the same effect.

[0115]

As described above, according to the first aspect of the invention, a fine structure having a high aspect ratio can be obtained, especially in the LIGA method.

Further, according to the present invention, a fine structure having a high aspect ratio, which could not be obtained without using a conventional large-sized high-performance synchrotron radiation device, in the LIGA method or the like, can be used for general-purpose synchrotron radiation. It can be formed using a synchrotron radiation device.

When the resist is exposed in a short time using a general-purpose synchrotron radiation device, the time required for forming a fine structure can be reduced.

The resolution of the resist can be improved by reducing the diffraction effect of light, that is, by using short-wavelength light. However, according to the present invention, it can also be improved by a chemical reaction mechanism and a development mechanism of the resist. .

According to the first aspect of the present invention, a thick resist layer can be formed and a resist pattern having a high aspect ratio can be formed. As a result, in the field of forming a three-dimensional structure by fine processing, particularly in the LIGA method or the like, By using the above-described resist according to the present invention, a fine structure having a high aspect ratio can be formed.

According to the second aspect of the present invention, a thick resist layer can be formed on a solid surface, and a resist pattern having an opening having a high aspect ratio can be easily formed. By etching and removing the solid portion exposed through the opening, a fine structure in which the solid portion is formed with unevenness having a high aspect ratio can be formed.

Further, when the X-ray mask according to the third invention is used, particularly in a method of forming a fine structure using the LIGA method, after forming a resist on a substrate in a thick film ,
Resist layer, even if a long time irradiation with X-ray of synchrotron radiation in the X-ray mask over according to the third aspect of the present invention, X-ray absorber film of the synchrotron radiation et
Since the box-ray can be sufficiently blocked, compared with the case of using the X-ray mask used in the manufacture of such a conventional semiconductor integrated circuit, a resist pattern having a high aspect ratio can be easily formed. D according to the third aspect of the present invention
By using a x- ray mask, a resist pattern having a high aspect ratio can be formed. As a result, a fine structure having a high aspect ratio can be formed in the field of forming a three-dimensional structure by microfabrication, particularly in the LIGA method. it can.

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing an embodiment of a process of forming a resist layer on a substrate according to the present invention.

FIG. 2 is a sensitivity comparison diagram of PMMA and a copolymer according to the present invention.

FIG. 3 is a process diagram schematically showing an embodiment of a process of forming an X-ray mask according to the present invention.

FIG. 4 is a process diagram schematically showing an embodiment of a process of forming an X-ray mask according to the present invention.

FIG. 5 shows a resist layer 1 in the step shown in FIG.
FIG. 5 is a process chart schematically showing a step of forming No. 5;

FIG. 6 is a schematic view schematically showing the steps of the LIGA method.

FIG. 7 is a schematic diagram schematically showing the steps of the LIGA method.

FIG. 8 is a cross-sectional view schematically showing an X-ray mask used in a conventional X-ray lithography method.

FIG. 9 is a schematic view schematically showing a step of forming an X-ray mask used in a conventional X-ray lithography method.

FIG. 10 is a schematic view schematically showing a step of forming an X-ray mask used in a conventional X-ray lithography method.

FIG. 11 is a diagram showing the correlation between the thickness of a resist that can be patterned in the thickness direction of a polymethyl methacrylate (PMMA) resist layer and the wavelength of X-rays.

FIG. 12 is a diagram showing a correlation between the film thickness of an X-ray absorber required as an X-ray mask used in manufacturing a micromachine or the like using the LIGA method or the like and the wavelength of X-rays.

[Explanation of symbols]

 1, 21 Hot plate 2, 11 Silicon substrate 3, 23 Spacer 4 24 Copolymer syrup 5, 25 Kapton sheet (release sheet) 6, 26 Metal plate 7, 27 Weight 12 X-ray transmission film 13 X-ray absorber film 13a X-ray Absorber film layer 14 Film 15 Resist layer 15a Resist pattern 15b Opening 40 X-ray mask

Continuation of the front page (56) References JP-A-56-64337 (JP, A) JP-A-61-29839 (JP, A) JP-A-56-128940 (JP, A) JP-A-56-53114 (JP, A) , A) JP-A-56-19044 (JP, A) JP-A-57-204033 (JP, A) International Publication No. WO 94/6058 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) G03F 7/00-7/42 H01L 21/027 G03F 1/16

Claims (3)

(57) [Claims] 1. A step of forming a resist layer on a substrate, and lithographically forming the resist layer by synchrotron radiation.
Forming a resist pattern by using a fiber.
In the method of forming a microstructure, the step of forming a resist layer on the substrate is performed by a general formula: Wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (a hydrogen atom of the alkyl group may be substituted with a halogen atom); and a monomer represented by the following general formula: Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group; and a prepolymerization of a monomer represented by the formula: fine to the step of applying the combined syrup on said substrate, wherein the coating step copolymer syrup layer formed on the substrate by, with a completion of the polymerization step of completely polymerized on said substrate The method of forming the structure. To 2. A solid surface, forming a resist layer, forming a resist pattern having an opening by lithography by synchrotron radiation in the resist layer, the resist pattern as a mask, Removing the solid portion exposed through the opening by etching. The step of forming a resist layer on the surface of the solid includes the following general formula: [Wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (a hydrogen atom of the alkyl group may be substituted with a halogen atom)], and a monomer represented by the following general formula: Wherein X is a halogen atom or a hydroxyl group, and R ₂ is a hydrogen atom or a methyl group; and a prepolymerization of a monomer represented by the formula: A step of applying the coalesced syrup on the surface of the solid; and a polymerization completion step of completely polymerizing the copolymer syrup layer formed on the surface of the solid by the application step on the surface of the solid . A method for forming a microstructure, comprising: 3. A resist layer on the surface of the X-ray absorber film.
Forming a resist pattern on the resist layer
Forming, and the X-ray absorption using the resist pattern as a mask
X-ray mask including a step of etching a body film
In the manufacturing method, (1) the step of forming the resist layer is performed by the general formula : Wherein R ₁ is an alkyl group having 1 to 4 carbon atoms (the alkyl group
May be substituted with a halogen atom)) and a monomer represented by the following general formula : Wherein X is a halogen atom or a hydroxyl group, and R ₂ is water
A monomer represented by the formula :
Preparing a copolymer syrup; and applying the copolymer syrup to the surface of the X-ray absorber membrane.
Coating on the surface of the X-ray absorber film by the coating step.
The formed copolymer syrup layer is completely covered on its surface.
A polymerization completion step of polymerizing, and (2)
A method of manufacturing an X-ray mask, wherein the average thickness of the X- ray absorber film is 5 μm or more .