JP2000181065A - Pattern forming material and pattern forming method - Google Patents

Abstract

(57) [PROBLEMS] To provide a resist pattern having a rectangular cross section when pattern exposure is performed on a chemically amplified resist film using an electron beam. SOLUTION: A positive type resin comprising a base resin which reacts in the presence of an acid to change to alkali-soluble, an acid generator which generates an acid when irradiated with an electron beam, and an amine compound having a boiling point of 250 ° C. or lower. Is applied on the semiconductor substrate 10 to form a resist film 11. When pre-baking the resist film 11, the amine concentration is inclined so that the amine concentration in the resist film 11 is low on the surface side and high on the substrate side. After pattern exposure is performed on the resist film 11 by the electron beam 13, heat treatment is performed to expose the exposed portion 1 of the resist film 11.
Change 1a to alkali-soluble. When the resist film 11 is developed using an alkaline developer, a resist pattern 14 having a rectangular cross-sectional shape is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pattern forming material and a pattern forming method used when fabricating a semiconductor integrated circuit by forming a fine resist pattern by using an electron beam lithography technique.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of an IC or an LSI, a resist pattern is formed by photolithography using ultraviolet rays or far ultraviolet rays, but a semiconductor integrated circuit is formed by miniaturization of a semiconductor element or adoption of an ASIC. With the progress of miniaturization, electron beam lithography has been used.

In order to form a fine resist pattern by electron beam lithography, a resist material having high sensitivity and high resolution is required, and a chemical amplification type resist material has been proposed to meet this demand. I have.

Hereinafter, a method for forming a resist pattern by performing pattern exposure using an electron beam on a resist film made of a chemically amplified resist material will be described with reference to FIGS. 7 (a) to 7 (e). .

First, as shown in FIG. 7A, an acid generator which generates an acid when irradiated with an electron beam is formed on a semiconductor substrate 1 by reacting in the presence of an acid with an alkaline aqueous solution. After forming a resist film 2 by applying a chemically amplified resist material containing a resin composition whose solubility in a developing solution changes, the semiconductor substrate 1 is heated by a hot plate 3 as shown in FIG. Then, prebaking is performed on the resist film 2.

Next, as shown in FIG. 7C, the resist film 2 is irradiated with an electron beam 4 to perform pattern exposure. In this way, in the exposed portion 2a of the resist film 2 where the electron beam 4 is irradiated, an acid is generated from the acid generator contained in the resist film 2, so that the solubility of the resin composition in the alkaline developer changes. on the other hand,
Since no acid is generated in the unexposed portion 2b, the solubility of the resin composition in the alkaline developer does not change.

Next, when the resist film 2 is developed with an alkaline developer, when a positive chemically amplified resist material is used, as shown in FIG.
The resist pattern 5A from which the exposed portion 2a is removed is obtained, and when a negative chemically amplified resist material is used, the unexposed portion 2b of the resist film 2 is removed as shown in FIG. Thus, the obtained resist pattern 5B is obtained.

[0008]

However, in electron beam lithography, due to a phenomenon called forward scattering,
There is a problem that it is difficult to form a resist pattern having a vertical cross-sectional shape. The forward scattering is a phenomenon in which the electron beam 4 is bent under the influence of the atoms contained in the resist material, so that the electron beam 4 spreads in the depth direction of the resist film 2 (substrate side). Although forward scattering occurs irrespective of the type of resist material, the chemical reaction or the dissolution rate contrast between the exposed portion 2a and the unexposed portion 2b is high, so that a chemical pattern capable of forming a resist pattern faithful to an electron beam image can be formed. Amplification type resist materials are particularly susceptible to forward scattering.

For this reason, when a positive chemically amplified resist is used, a resist pattern 5A having a reverse tapered cross section is obtained as shown in FIG. 7D, and a negative chemically amplified resist is obtained. When a resist is used, there is a problem that a resist pattern 5B having a forward tapered cross section is obtained as shown in FIG.

In view of the above, the present invention provides a resist pattern having a rectangular cross section when a chemically amplified resist film is subjected to pattern exposure using an electron beam to form a resist pattern. The purpose is to.

[0011]

In order to achieve the above-mentioned object, a pattern-forming material according to the present invention comprises a resin composition which reacts in the presence of an acid to change its solubility in an alkaline developer, and an electron beam. It contains an acid generator that generates an acid upon irradiation and an amine compound having a boiling point of 250 ° C. or less.

According to the pattern forming material of the present invention, since it contains an amine compound having a boiling point of 250 ° C. or less,
When a resist film is formed by applying the pattern forming material of the present invention on a substrate, the amine concentration distribution in the resist film has a gradient such that the concentration of amine contained in the resist film is low on the surface side and high on the substrate side. The width of the concentration distribution of the remaining acid generated by the acid generator and neutralized by the amine in the exposed portion of the film becomes substantially equal between the surface side and the substrate side in the resist film.

In the pattern forming material of the present invention, the amine compound is preferably tributylamine or phenylpropylamine.

In order to achieve the above object, a pattern forming method according to the present invention provides a resin composition which changes its solubility in an alkaline developer by reacting with the presence of an acid, and generates an acid by irradiation with an electron beam. A first step of applying a chemically amplified resist material containing an acid generator and an amine compound on a semiconductor substrate to form a resist film, and a step in which the concentration of amine contained in the resist film is low on the surface side and the substrate side is low. A second step of providing a gradient in the concentration distribution of the amine contained in the resist film so as to increase the concentration, and performing a pattern exposure with an electron beam on the resist film in which the concentration distribution of the amine has a gradient. A third step of generating an acid from an acid generator in an exposed portion of the film, and a heat treatment on the resist film in which the acid is generated in the exposed portion, to reduce the action of the acid. A fourth step of changing the solubility of the exposed portion in an alkaline developer, and developing the resist film in which the solubility of the exposed portion in the alkaline developer is changed using an alkaline developer to form a resist pattern. A fifth step of forming

According to the pattern forming method of the present invention, the amine compound is contained in the chemically amplified resist material, and the amine concentration distribution is such that the amine concentration contained in the resist film is low on the surface side and high on the substrate side. The width of the concentration distribution of the remaining acid, which is generated from the acid generator in the exposed portion of the resist film and then neutralized by the amine after exposure from the acid generator in the exposed portion of the resist film, is different from the surface side of the resist film and the substrate side. And become almost equal.

In the pattern forming method of the present invention, the amine compound contained in the chemically amplified resist material has a boiling point of 2
Preferably, the temperature is 50 ° C. or lower, and the second step includes a step of giving a gradient to the concentration distribution of amine contained in the resist film by pre-baking the resist film.

In the pattern forming method of the present invention, the second
The step (b) preferably includes a step of giving a gradient to the concentration distribution of amine contained in the resist film by performing a heat treatment on the resist film under reduced pressure.

In the pattern forming method of the present invention, the second
The step preferably includes a step of giving a gradient to the concentration distribution of amine contained in the resist film by performing a heat treatment on the resist film and then maintaining the resist film under reduced pressure.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A positive pattern forming material and a pattern forming method will be described as a first embodiment of the present invention with reference to FIGS.

In the first embodiment, the concentration distribution in the depth direction of the amine is inclined by using a positive chemically amplified resist material containing an amine compound having a boiling point of 250 ° C. or lower. .

First, a base resin that reacts in the presence of an acid to change to alkali-soluble, an acid generator that generates an acid when irradiated with an electron beam, and an amine compound having a boiling point of 250 ° C. or less are used as a solvent. A melted liquid chemically amplified resist material is prepared.

Examples of the base resin include novolak resins, polyvinylphenol resins, resins of polyvinylphenol derivatives and polyhydroxystyrene derivatives. When a base resin is made of a poorly-soluble alkali such as a polyhydroxystyrene derivative, a two-component resist material is used. As the base resin, a base-soluble resin such as a novolak resin or a polyvinylphenol resin is used. When used, a three-component resist material is obtained by incorporating a dissolution inhibitor.

Examples of the acid generator include onium salts such as sulfonium salts and iodonium salts, sulfonic acid esters,
Examples thereof include a diazodisulfone compound and a ketosulfone compound.

As amine compounds having a boiling point of 250 ° C. or less, tributylamine (boiling point: 220 ° C.), NMP (boiling point: 202 ° C.), tributylpyridine (boiling point: 230 ° C.)
° C), 3-aminopyridine (boiling point: 248 ° C), trimethylpyridine (boiling point: 172 ° C), benzyldimethylamine (boiling point: 180 ° C), dibutylethanolamine (boiling point: 230 ° C), phenylethylamine (boiling point: 1)
95 ° C), phenylpropylamine (boiling point: 220 ° C)
Or dibutylamine (boiling point: 159 ° C.).

As the solvent, those which can dissolve the above-mentioned base resin, acid generator and amine compound can be appropriately used.

Hereinafter, the first embodiment will be described in detail.

First, a resist material having the following composition is prepared.

Base resin: poly [4- (1-ethoxyethoxy) styrene-co-4-hydroxystyrene]
1 g Acid generator: dinitrobenzyl tosylate 30 mg Amine compound: tributylamine 5 mg Solvent: propylene glycol monomethyl ether acetate 4 g Dissolve the above base resin, acid generator and amine compound in the above solvent and liquid After the resist material is prepared, the resist material is spin-coated to form a resist film 11 on the semiconductor substrate 10 as shown in FIG.

Next, as shown in FIG. 1B, the semiconductor film 10 is heated for 2 minutes using a hot plate 12 at 120.degree. Resist film 1 having a thickness of
Get 1. Since tributylamine has a low boiling point of 220 ° C., it tends to volatilize from the surface of the resist film 11 by pre-baking. For this reason, as shown in FIG. 2, the amine compound (tributylamine) has a concentration gradient in the depth direction, and has a low concentration on the surface side of the resist film 11 and a high concentration on the substrate side of the resist film 11.

Next, as shown in FIG. 1C, pattern exposure is performed on the resist film 11 by using, for example, an electron beam 13 having an acceleration voltage of 50 keV. At this time, since the electron beam 13 is scattered forward in the resist film 11, the image of the electron beam 13 spreads toward the substrate side of the resist 11.
a has a forward tapered cross section and a resist film 1
The one unexposed portion 11b has a reverse tapered cross-sectional shape. Since the acid is generated from the acid generator in the exposed portion 11a of the resist film 11, the distribution of the acid also increases toward the substrate side.

Next, the semiconductor substrate 10 is subjected to a heat treatment (P
EB: baking after exposure) to form a resist film 1
By diffusing the acid generated in the first exposed portion 11a, a part of the generated acid and the amine compound are neutralized, and the base resin is alkalized by the catalytic action of the acid remaining unneutralized. Change to soluble.

Next, when the resist film 11 is developed using an alkaline developing solution, as shown in FIG. 1D, a 0.12 μm line-and-space resist having a rectangular cross-sectional shape is formed. A pattern 14 is obtained.

FIG. 3A shows the concentration distribution of the acid and the amine on the surface side of the resist film 11, and FIG. 3B shows the concentration distribution of the acid and the amine on the substrate side of the resist film 11. 3A and 3B, a thin solid line indicates the concentration distribution of the acid immediately after the irradiation with the electron beam (EB), a broken line indicates the concentration distribution of the amine compound, and a thick solid line indicates the concentration of the amine compound. The concentration distribution of the acid after the sum reaction is shown. Note that, as shown in FIG. 3A, at the interface between the exposed portion and the unexposed portion immediately after the electron beam exposure, the acid concentration distribution has a slight spread, and as shown in FIG. At the interface between the exposed portion and the unexposed portion immediately after the electron beam exposure, the acid concentration distribution has a large spread due to forward scattering.

As shown in FIG. 3A, the resist film 11
On the surface side of the exposed portion 11a, the spread of the acid immediately after the EB exposure is small, and the amine has a low boiling point. 3B does not change much while the spread width remains small, and as shown in FIG. 3B, on the substrate side in the exposed portion of the resist film 11, the spread width of the acid immediately after the EB exposure is large and the amine does not volatilize. Since the concentration of the amine is high, the spread of the concentration distribution of the acid after neutralization is greatly reduced. Therefore, FIG. 3A and FIG.
As can be seen from the comparison with FIG. 3B, the spread width of the acid concentration distribution after neutralization in the exposed portion 11a of the resist film 11 is substantially equal between the surface side and the substrate side.
As shown in (c), the cross-sectional shape of the resist pattern 14 is rectangular.

FIGS. 4A to 4C show a state in which the cross-sectional shape of the resist pattern 14 becomes slightly tapered when the concentration of the amine contained in the resist film 11 is high. On the surface side of the resist film 11, the concentration of the amine is high but the amount of the volatilized amine is large. Therefore, as shown in FIG. 4 (a), the acid concentration distribution after neutralization is shown in FIG. 3 (a). As in the case, on the substrate side of the resist film 11, since the concentration of the amine is high and the amine hardly volatilizes, the concentration distribution of the acid after neutralization is as shown in FIG. It becomes narrower than the case shown in FIG. As a result, as shown in FIG. 4C, the cross-sectional shape of the resist pattern 14 has a slightly inverted tapered shape.

FIGS. 5A to 5C show a state where the cross-sectional shape of the resist pattern 14 becomes slightly forward tapered when the concentration of the amine contained in the resist film 11 is low. On the surface side of the resist film 11, the concentration of the amine is low but the amount of the volatilized amine is small.
As shown in FIG. 5, the concentration distribution of the acid after neutralization is the same as that shown in FIG. 3A. However, since the concentration of the amine is low on the substrate side of the resist film 11, FIG. As shown, the concentration distribution of the acid after neutralization is narrower than in the case shown in FIG. As a result, as shown in FIG. 5C, the cross-sectional shape of the resist pattern 14 has a slightly inverted tapered shape.

FIGS. 4A to 4C show the resist film 1.
5A to 5C illustrate the case where the amine concentration included in the resist film 11 is low, and FIGS. 5A to 5C illustrate the case where the amine concentration included in the resist film 11 is low.
5A to 5C correspond to the case where the amine compound contained in the resist film 11 has a low boiling point.
(A) to (c) also apply to the case where the concentration of the amine compound contained in the resist film 11 is high.

From such a viewpoint, when an amine compound having a boiling point of about 220 ° C., for example, tributylamine or phenylpropylamine is contained in a chemically amplified resist material, it depends on the kind of acid generator, but it is generally used. When an acid generator is used, the amine concentration distribution is shown in FIG.
3A and 3B, the obtained resist pattern 14 has a vertical cross-sectional shape as shown in FIG. 3C.

(Second Embodiment) A negative pattern forming material and a pattern forming method will be described below as a second embodiment of the present invention with reference to FIG.

In the second embodiment, a gradient is applied to the concentration distribution of amine in the depth direction by using a negative chemically amplified resist material containing an amine compound having a boiling point of 250 ° C. or lower.

First, a liquid obtained by dissolving an alkali-soluble base resin, a cross-linking agent for cross-linking the base resin in the presence of an acid to change the base resin to be hardly soluble in alkali, and an amine compound having a boiling point of 250 ° C. or lower in a solvent. Prepare a chemically amplified resist material.

Examples of the base resin include a polyvinylphenol derivative resin and a novolak resin.

Examples of the crosslinking agent include melamine and the like.

Examples of the acid generator include onium salts such as sulfonium salts and iodonium salts, sulfonic acid esters,
Examples thereof include a diazodisulfone compound and a ketosulfone compound.

As the amine compound having a boiling point of 250 ° C. or less, tributylamine (boiling point:
220 ° C), NMP (boiling point: 202 ° C), tributylpyridine (boiling point: 230 ° C), 3-aminopyridine (boiling point: 248 ° C), trimethylpyridine (boiling point: 172)
° C), benzyldimethylamine (boiling point: 180 ° C), dibutylethanolamine (boiling point: 230 ° C), phenylethylamine (boiling point: 195 ° C), phenylpropylamine (boiling point: 220 ° C) or dibutylamine (boiling point: 1)
59 ° C.).

As the solvent, those which can dissolve the above-mentioned base resin, crosslinking agent, acid generator and amine compound can be used as appropriate.

Hereinafter, the second embodiment will be described in detail.

First, a resist material having the following composition is prepared.

Base resin: poly (4-hydroxystyrene-co-styrene) 1 g Acid generator: dinitrobenzyl tosylate 40 mg Crosslinking agent: 1,3,5-tris (isopropoxymethoxy) benzene 0. 4 g Amine compound: phenylpropylamine 10 mg Solvent: propylene glycol monomethyl ether acetate 5 g The above base resin, acid generator, crosslinking agent, and amine compound are dissolved in the above solvent to prepare a liquid resist material. A resist material is spin-coated to form a resist film 21 on the semiconductor substrate 20, as shown in FIG.

Next, as shown in FIG. 2 (b), the resist film 21 is prebaked by heating the semiconductor substrate 20 using a hot plate 22 at 120.degree. Resist film 2 having a thickness of
Get 1. Since phenylpropylamine has a low boiling point of 220 ° C., the resist film 21 is prebaked.
Easily volatilizes from the surface of For this reason, the amine compound (phenylpropylamine) has a concentration gradient in the depth direction,
The concentration is low on the surface side of the resist film 21 and the resist film 2
The density increases on the substrate side of No. 1.

Next, as shown in FIG. 2C, pattern exposure is performed on the resist film 21 by using, for example, an electron beam 23 having an acceleration voltage of 50 keV. At this time, since the forward scattering of the electron beam 23 occurs in the resist film 21, the image of the electron beam 23 spreads toward the substrate side of the resist 21.
a has a forward tapered cross section and a resist film 2
The one unexposed portion 21b has a reverse tapered cross-sectional shape. Since the acid is generated from the acid generator in the exposed portion 21a of the resist film 21, the distribution of the acid also increases toward the substrate side.

Next, the semiconductor substrate 20 is subjected to a heat treatment (P
EB: baking after exposure) to form a resist film 2
By diffusing the acid generated in the exposed portion 21a, a part of the generated acid and the amine compound are neutralized, and the catalytic action of the acid remaining unneutralized and the action of the crosslinking agent This causes a crosslinking reaction in the base resin to change the base resin to alkali-insoluble.

Next, when the resist film 21 is developed using an alkaline developing solution, as shown in FIG. 2D, a 0.10 μm line-and-space resist having a rectangular cross-sectional shape is formed. A pattern 24 is obtained.

According to the second embodiment, the resist film 21
On the surface side of the exposed portion 21a, the spread width of the acid immediately after EB exposure is small and the amine concentration is also low because the boiling point of the amine compound is low, so the spread width of the acid concentration distribution after neutralization remains small. While it does not change much,
On the substrate side in the exposed portion of the resist film 21, E
Immediately after the exposure to B, the spread of the acid is large and the amine compound does not volatilize, so that the concentration of the amine is increased. Therefore, the spread of the concentration distribution of the acid after neutralization is greatly reduced. For this reason, the spread width of the acid concentration distribution after the neutralization in the exposed portion 21a of the resist film 21 is substantially equal between the surface side and the substrate side, so that the cross-sectional shape of the resist pattern 24 is rectangular.

(Third Embodiment) Hereinafter, a positive pattern forming material and a pattern forming method will be described as a third embodiment of the present invention.

In the third embodiment, a positive chemical amplification type resist material containing an amine compound is used, and pre-baking is performed on the resist film under reduced pressure, so that the concentration distribution of the amine in the depth direction is reduced. This is the case.

First, a base resin that reacts in the presence of an acid to change to alkali solubility, an acid generator that generates an acid when irradiated with an electron beam, and a liquid chemical obtained by dissolving an amine compound in a solvent. Prepare an amplification type resist material.

Examples of the base resin include novolak resins, polyvinylphenol resins, resins of polyvinylphenol derivatives and polyhydroxystyrene derivatives. When a base resin having a poor alkali solubility such as a polyhydroxystyrene derivative is used, a two-component positive resist material is used. As the base resin, an alkali-soluble resin such as a novolak resin or a polyvinylphenol resin is used. If you use
When a dissolution inhibitor is contained, a three-component positive resist material is obtained.
It becomes a component type negative resist material.

Examples of the acid generator include onium salts such as sulfonium salts and iodonium salts, sulfonic acid esters,
Examples thereof include a diazodisulfone compound and a ketosulfone compound.

As amine compounds, tributylamine (boiling point: 220 ° C.), NMP (boiling point: 202 ° C.), tributylpyridine (boiling point: 230 ° C.), 3-aminopyridine (boiling point: 248 ° C.), 4-aminopyridine (boiling point: 248 ° C.) Boiling point: 2
84 ° C), trimethylpyridine (boiling point: 172 ° C), benzyldimethylamine (boiling point: 180 ° C), dibutylethanolamine (boiling point: 230 ° C), phenylethylamine (boiling point: 195 ° C), phenylpropylamine (boiling point: 220 ° C) , Dicyclohexylamine (boiling point: 25
8 ° C.), dibutylamine (boiling point: 159 ° C.), trioctylamine (boiling point: 367 ° C.) or dicyclohexylmethylamine (boiling point: 270 ° C.).

As the solvent, those which can dissolve the above-mentioned base resin, acid generator and amine compound can be appropriately used.

Hereinafter, the third embodiment will be described in detail.

First, a resist material having the following composition is prepared.

Base resin: poly (4-hydroxystyrene-co-4-t-butoxycarbonyloxystyrene) 1 g Acid generator: 1,2,3-trismethylsulfonyloxybenzene 30 mg Amine compound: dicyclohexylamine 5 mg Solvent: ethyl lactate 4 g After dissolving the above base resin, acid generator and amine compound in the above solvent to prepare a liquid resist material, spin coating the resist material on a semiconductor substrate to form a resist. Form a film.

Next, under reduced pressure, for example, 1 × 10 ⁻¹² Torr
Under the conditions described above, the semiconductor substrate is heated using a hot plate at 120 ° C. for 2 minutes to pre-bake the resist film. Since the resist film is prebaked under reduced pressure, the amine compound (dicyclohexylamine) has a concentration gradient in the depth direction, and the concentration is low on the surface side of the resist film and low on the substrate side of the resist film. Get higher.

Next, pattern exposure is performed on the resist film by, for example, an electron beam having an acceleration voltage of 50 keV. At this time, since the electron beam is scattered forward in the resist film, the image of the electron beam spreads toward the substrate side of the resist, so that the exposed portion of the resist film has a forward tapered cross-sectional shape. Since the acid is generated from the acid generator in the exposed portion of the resist film, the distribution of the acid also increases toward the substrate side.

Next, heat treatment (PE) is performed on the semiconductor substrate.
B: baking after exposure) to diffuse the acid generated in the exposed part of the resist film,
A part of the generated acid is subjected to a neutralization reaction with the amine compound, and the base resin is converted to alkali-soluble by the catalytic action of the acid remaining unneutralized.

Next, when the resist film is developed using an alkaline developer, a 0.1 μm line-and-space resist pattern having a rectangular cross-sectional shape is obtained.

According to the third embodiment, on the surface side of the exposed portion of the resist film, the spread width of the acid immediately after the EB exposure is small, and the pre-baking is performed under reduced pressure. While the width of the subsequent acid concentration distribution remains small and does not change much, on the substrate side in the exposed portion of the resist film, the acid spread immediately after the EB exposure is large and the amine compound is not volatilized because the amine compound does not volatilize. Since it is high, the spread of the concentration distribution of the acid after neutralization is greatly reduced. For this reason, the width of spread of the concentration distribution of the acid after neutralization in the exposed portion of the resist film becomes substantially equal between the surface side and the substrate side, so that the cross-sectional shape of the resist pattern becomes rectangular.

(Fourth Embodiment) Hereinafter, a positive pattern forming material and a pattern forming method will be described as a fourth embodiment of the present invention.

In the fourth embodiment, a positive chemically amplified resist material containing an amine compound is used, and the resist film is prebaked and then kept under reduced pressure to thereby reduce the amine concentration in the depth direction. This is the case where the distribution has a gradient.

First, a base resin which reacts in the presence of an acid to change to alkali solubility, an acid generator which generates an acid when irradiated with an electron beam, and a liquid chemical obtained by dissolving an amine compound in a solvent. Prepare an amplification type resist material.

Examples of the base resin include a novolak resin, a polyvinylphenol resin, and a resin of a polyvinylphenol derivative or a polyhydroxystyrene derivative. When a base resin having a poor alkali solubility such as a polyhydroxystyrene derivative is used, a two-component positive resist material is used. As the base resin, an alkali-soluble resin such as a novolak resin or a polyvinylphenol resin is used. If you use
When a dissolution inhibitor is contained, a three-component positive resist material is obtained.
It becomes a component type negative resist material.

Examples of the acid generator include onium salts such as sulfonium salts and iodonium salts, sulfonic esters,
Examples thereof include a diazodisulfone compound and a ketosulfone compound.

As the amine compound, tributylamine (boiling point: 220 ° C.), NMP (boiling point: 202 ° C.), tributylpyridine (boiling point: 230 ° C.), 3-aminopyridine (boiling point: 248 ° C.), 4-aminopyridine (boiling point: 248 ° C.) Boiling point: 2
84 ° C), trimethylpyridine (boiling point: 172 ° C), benzyldimethylamine (boiling point: 180 ° C), dibutylethanolamine (boiling point: 230 ° C), phenylethylamine (boiling point: 195 ° C), phenylpropylamine (boiling point: 220 ° C) , Dicyclohexylamine (boiling point: 25
8 ° C.), dibutylamine (boiling point: 159 ° C.) or dicyclohexylmethylamine (boiling point: 270 ° C.).

As the solvent, those which can dissolve the above-mentioned base resin, acid generator and amine compound can be appropriately used.

Hereinafter, the fourth embodiment will be described in detail.

First, a resist material having the following composition is prepared.

Base resin: poly (4-hydroxystyrene-co-4-t-butoxystyrene) 1 g Acid generator: bisphenylsulfonyldiazomethane 3
0 mg Amine compound: tributylpyridine 8 mg Solvent: ethyl lactate 4 g After dissolving the above base resin, acid generator and amine compound in the above solvent to prepare a liquid resist material, spin the resist material on a semiconductor substrate. Coating to form a resist film.

Next, the semiconductor film is prebaked by heating the semiconductor substrate using a hot plate at 120 ° C. for 2 minutes, and then the resist film is reduced under reduced pressure, for example, at 1 × 10 ⁻¹² Torr. Keep under conditions.
Thus, the amine compound (bisphenylsulfonyldiazomethane) has a concentration gradient in the depth direction so that the resist film after pre-baking is kept under reduced pressure, the concentration is low on the surface side of the resist film and the substrate side of the resist film Increases the concentration.

Next, pattern exposure is performed on the resist film by, for example, an electron beam having an acceleration voltage of 50 keV. At this time, since the electron beam is scattered forward in the resist film, the image of the electron beam spreads toward the substrate side of the resist, so that the exposed portion of the resist film has a forward tapered cross-sectional shape. Since the acid is generated from the acid generator in the exposed portion of the resist film, the distribution of the acid also increases toward the substrate side.

Next, heat treatment (PE) is performed on the semiconductor substrate.
B: baking after exposure) to diffuse the acid generated in the exposed part of the resist film,
A part of the generated acid is subjected to a neutralization reaction with the amine compound, and the base resin is converted to alkali-soluble by the catalytic action of the acid remaining unneutralized.

Next, when the resist film is developed using an alkaline developing solution, a 0.1 μm line-and-space resist pattern having a rectangular cross-sectional shape is obtained.

According to the fourth embodiment, on the surface side of the exposed portion of the resist film, the spread of the acid immediately after the EB exposure is small, and the pre-baked resist film is held under reduced pressure, so that the amine concentration is low. Therefore, while the width of the acid concentration distribution after neutralization remains small and does not change much, on the substrate side in the exposed portion of the resist film, the acid spread immediately after the EB exposure is large and the amine compound does not volatilize. Therefore, since the concentration of the amine is high, the spread width of the concentration distribution of the acid after neutralization is greatly reduced. For this reason, the width of spread of the concentration distribution of the acid after neutralization in the exposed portion of the resist film becomes substantially equal between the surface side and the substrate side, so that the cross-sectional shape of the resist pattern becomes rectangular.

[0085]

According to the pattern-forming material of the present invention, since it contains an amine compound having a boiling point of 250 ° C. or less, the remaining portion neutralized by the amine after being generated from the acid generator in the exposed portion of the resist film. Since the spread width of the acid concentration distribution is substantially equal between the surface side and the substrate side of the resist film, the obtained resist pattern has a rectangular cross-sectional shape.

In the pattern forming material of the present invention, when the amine compound is tributylamine or phenylpropylamine, the difference between the surface side of the resist film and the substrate side in the spread width of the concentration distribution of the acid after neutralization by the amine. Is almost eliminated, so that the cross-sectional shape of the obtained resist pattern becomes more rectangular.

According to the pattern forming method of the present invention, the amine compound is contained in the chemically amplified resist material, and the amine concentration distribution is such that the concentration of amine contained in the resist film is low on the surface side and high on the substrate side. The width of the concentration distribution of the remaining acid, which is generated from the acid generator in the exposed portion of the resist film and then neutralized by the amine after exposure from the acid generator in the exposed portion of the resist film, is different from the surface side of the resist film and the substrate side. And the resulting resist pattern has a rectangular cross-sectional shape.

In the pattern forming method of the present invention, the amine compound contained in the chemically amplified resist material has a boiling point of 2
The temperature is 50 ° C. or lower, and if the second step includes a step of giving a gradient to the concentration distribution of amine by pre-baking the resist film, it is indispensable to form a resist film made of a chemically amplified resist material. In the pre-baking step, the concentration distribution of the amine can be inclined, so that the cross-sectional shape of the obtained resist pattern can be made rectangular without increasing the number of steps.

In the pattern forming method of the present invention, the second
The step of performing a heat treatment on the resist film under reduced pressure to impart a gradient to the concentration distribution of the amine, even if the amine compound having a considerably high boiling point is contained in the chemically amplified resist material, Can be made to have a gradient, so that the cross-sectional shape of the obtained resist pattern can be reliably made rectangular.

In the pattern forming method of the present invention, the second
The step of performing a heat treatment on the resist film and then holding the resist film under reduced pressure to impart a gradient to the concentration distribution of the amine. Even in the case of being included in the amplification type resist material, the amine concentration distribution can be inclined, so that the cross-sectional shape of the obtained resist pattern can be reliably made rectangular.

Therefore, according to the pattern forming material or the pattern forming method of the present invention, even when the resist film is subjected to the pattern exposure using the electron beam, even if the electron beam scattering phenomenon occurs, the rectangular cross section can be formed. Since it becomes possible to obtain an excellent resist pattern, it is possible to cope with further miniaturization of a semiconductor integrated circuit.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views showing each step of a pattern forming method according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of amine concentration after pre-baking in the pattern forming method according to the first embodiment.

FIG. 3A is a diagram illustrating a concentration distribution of an acid and an amine on the surface side of a resist film obtained by a pattern forming method according to the first embodiment, and FIG. 3B is a diagram illustrating the concentration distribution according to the first embodiment; FIG. 3 is a diagram illustrating a concentration distribution of an acid and an amine on a substrate side of a resist film obtained by a pattern forming method, and FIG. 4C is a diagram illustrating a cross-sectional shape of a resist pattern obtained by a pattern forming method according to the first embodiment. is there.

FIGS. 4A to 4C show the case where the concentration of amine is high in the pattern forming method according to the first embodiment, and FIG. 4A shows the concentration distribution of acid and amine on the surface side of the resist film; (B) is a diagram showing the concentration distribution of acid and amine on the substrate side of the resist film,
(C) is a diagram showing a cross-sectional shape of the obtained resist pattern.

FIGS. 5A to 5C show the case where the concentration of amine is low in the pattern forming method according to the first embodiment, and FIG. 5A shows the concentration distribution of acid and amine on the surface side of the resist film; (B) is a diagram showing the concentration distribution of acid and amine on the substrate side of the resist film,
(C) is a diagram showing a cross-sectional shape of the obtained resist pattern.

FIGS. 6A to 6D are cross-sectional views showing respective steps of a pattern forming method according to a second embodiment of the present invention.

FIGS. 7A to 7E are cross-sectional views showing each step of a conventional pattern forming method and the shape of a resist pattern obtained.

[Explanation of symbols]

 Reference Signs List 10 semiconductor substrate 11 resist film 11a exposed portion 11b unexposed portion 12 hot plate 13 electron beam 14 resist pattern 20 semiconductor substrate 21 resist film 21a exposed portion 21b unexposed portion 22 hot plate 23 electron beam 24 resist pattern

Claims (6)

[Claims] 1. A resin composition which reacts in the presence of an acid to change its solubility in an alkaline developer, an acid generator which generates an acid by irradiation with an electron beam, and a boiling point of 250 ° C.
A pattern forming material, comprising: an amine compound described below. 2. The pattern forming material according to claim 1, wherein the amine compound is tributylamine or phenylpropylamine. 3. A chemically amplified resist material comprising a resin composition which reacts in the presence of an acid to change its solubility in an alkaline developer, an acid generator which generates an acid by irradiation with an electron beam, and an amine compound. A resist film is formed on a semiconductor substrate, and a concentration of the amine contained in the resist film is adjusted so that the concentration of the amine contained in the resist film is low on the surface side and high on the substrate side. A second step of giving a gradient to the distribution, and performing a pattern exposure by an electron beam on the resist film having a gradient of the amine concentration distribution to generate an acid from the acid generator in an exposed portion of the resist film. A third step of performing heat treatment on the resist film in which acid is generated in the exposed portion, and reacting the resist film with the alkaline developer in the exposed portion by the action of the acid. A fourth step of changing the solubility of the resist film, and a fifth step of developing a resist film having a changed solubility of the exposed portion in an alkaline developer using an alkaline developer to form a resist pattern. And a pattern forming method comprising: 4. The method according to claim 1, wherein the amine compound contained in the chemically amplified resist material has a boiling point of 250 ° C. or less. 4. A pattern forming method according to claim 3, further comprising the step of giving a gradient to the density distribution of the pattern. 5. The method according to claim 1, wherein the second step includes a step of performing a heat treatment on the resist film under reduced pressure to give a gradient to the concentration distribution of amine contained in the resist film. The pattern forming method according to claim 3. 6. In the second step, after performing a heat treatment on the resist film, the resist film is held under reduced pressure, so that the concentration distribution of amine contained in the resist film has a gradient. 4. The pattern forming method according to claim 3, further comprising the step of: