JP2001222109A - Exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the light transmittance of a resist layer and to enable microfabrication on a further minute level. SOLUTION: When a resist layer is patterned in a prescribed shape by selective exposure with X-rays, vacuum UV, extreme-ultraviolet radiation or soft X-rays, a high molecular material obtained by extending the π electron system of an aromatic ring in an aromatic ring-containing existing resist material is used as a high molecular material constituting the resist layer. The proportion of oxygen atoms to all the constituent atoms of the high molecular material is relatively reduced and the optical absorption of the entire high molecular material is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for performing ultra-fine processing in, for example, a semiconductor field.

[0002]

2. Description of the Related Art In the field of semiconductors, for example, with the increase in the degree of integration of semiconductor elements, it is urgently necessary to establish a new process technology capable of processing an extremely fine pattern of, for example, 0.1 μm or less.

In order to process a fine pattern, a so-called lithography technique is indispensable. In order to improve the optical resolution by shortening the exposure wavelength and to cope with ultra-fine processing, a conventional mercury lamp or excimer laser is used. In addition to ultraviolet light, extreme ultraviolet light having a wavelength of about 7 nm to 16 nm (EU)
V: Extreme ultraviolet) is being developed energetically.

[0004]

However, in the extreme ultraviolet EUV wavelength region, the ordinary resist material has a large optical absorption, and the irradiated light does not reach the lower part of the resist layer, so that the resist pattern is not formed. There is a problem of deterioration.

The deterioration of the resist pattern greatly hinders ultrafine processing, and its improvement is desired.

The present invention has been proposed to solve such a problem, and solves the problem of the light transmittance of the resist layer in the wavelength region of extreme ultraviolet EUV, thereby enabling further finer processing than before. It is an object of the present invention to provide a simple exposure method.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method of selectively exposing a resist layer to any one of X-rays, vacuum ultraviolet rays, extreme ultraviolet rays and soft X-rays. In the exposure method of patterning, as a polymer material constituting the resist layer, a polymer material in which the π-electron system of the aromatic ring in the existing resist material containing an aromatic ring is further expanded, a compound represented by the following formula 3, and It is characterized in that at least one of the compounds represented by the following formula (4) is used.

[0008]

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[0009]

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[0010] Here, the existing resist material refers to all resist materials known before the filing of the present application.

Usually, the polymer material constituting the resist layer must have an oxygen atom in order to exhibit resist characteristics. In the polymer material, the part that causes some chemical reaction due to the irradiation light, changes the physical property values of the irradiated part and the non-irradiated part, and causes the development of the resist characteristics,
It is a group that always contains oxygen, such as an ester group, a phenol group, an alcohol group, and a carboxyl group.

In the extreme ultraviolet EUV wavelength region, the optical absorption of oxygen is greater than that of carbon or hydrogen, which causes a decrease in the light transmittance of the polymer material. The optical absorption per oxygen atom is as large as about three times that of carbon atoms and about 50 to 100 times that of hydrogen atoms.

In the present invention, the polymer material constituting the resist layer is a polymer material having a more expanded π-electron system of the aromatic ring in the existing resist material containing an aromatic ring, and is represented by the structural formula (1). Wherein φ is an aromatic or heterocyclic ring other than a benzene ring, for example, a compound having a structure larger than a benzene ring such as a naphthalene ring, and φ represented by the structural formula (2) is an aromatic or heterocyclic ring other than a benzene ring; For example, at least one of compounds having a structure larger than a benzene ring such as a naphthalene ring. Accordingly, in the polymer material forming the resist layer, the ratio of oxygen atoms to the atoms forming the polymer material is relatively reduced, and the optical absorption of the entire polymer material is suppressed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an exposure method to which the present invention is applied will be described in detail.

The exposure method of the present invention is applied to, for example, processing of an extremely fine pattern in a semiconductor device.
Specifically, a step of applying and forming a resist layer having a photosensitive action on the substrate, and a step of selectively exposing the resist layer to one of X-rays, vacuum ultraviolet rays, extreme ultraviolet rays, and soft X-rays, and And developing the resist layer into a predetermined pattern by development.

As the exposure wavelength for exposure, any one of X-rays, vacuum ultraviolet rays, extreme ultraviolet rays, and soft X-rays can be used. In particular, extreme ultraviolet rays having a wavelength of 7 nm to 16 nm are used. This enables exposure at a higher resolution than ever before.

At the time of exposure, for example, exposure is performed by reduction projection using a reduction projection optical system.

The polymer material used for the resist layer is as follows:
For example, novolak resin, polyhydroxystyrene resin,
The basic skeleton is an acrylic resin, a siloxane resin having an ester group, a carboxyl group or a phenol group, a silsesquioxane resin, a polycycloolefin resin, or the like.

These polymer materials often contain an aromatic ring such as a benzene ring. This is because when these polymer materials contain an aromatic ring, the etching resistance of the resist material becomes better.

In the resin serving as the basic skeleton, a part causing a chemical reaction due to the irradiation light, causing a change in the physical property values of the irradiated part and the unirradiated part, and causing a resist characteristic to be developed is an ester group, A group containing oxygen, such as a phenol group, an alcohol group, and a carboxyl group.

The optical absorption in the extreme ultraviolet EUV wavelength region is, for example, 7 nm, Si>F>O>N>C>.
H>Si>F>O>N>C> even at 10 nm and 11 nm
H, 12 nm, F>Si>O>N>C> H, 13 nm
And at 16 nm, F>O>N>C>Si> H are larger in this order. That is, containing oxygen is disadvantageous from the viewpoint of optical absorption in the wavelength region of extreme ultraviolet EUV of the polymer material.

Therefore, in the present invention, the ratio of carbon atoms and hydrogen atoms to oxygen atoms is increased to reduce the absorption of the polymer material used as a resist material in the extreme ultraviolet EUV wavelength region. Will be diluted.

As the polymer material constituting the resist layer, a polymer material having the above basic skeleton, a polymer material obtained by further expanding the π electron system of the aromatic ring in the existing resist material containing an aromatic ring, and a structural formula ( At least one of the compound represented by 1) and the compound represented by Structural Formula (2) is used.

Specifically, it has the above basic skeleton,
Π of aromatic ring in existing resist materials containing aromatic ring
Examples of the polymer material having a more expanded electronic system include those obtained by replacing the benzene ring portion of an existing resist material containing a benzene ring with a naphthalene ring, an anthracene ring, or the like. In a polymer material obtained by expanding the π-electron system of an aromatic ring, the proportion of carbon atoms and hydrogen atoms in the atoms constituting the polymer material is increasing.

In the compound represented by the structural formula (1) and the compound represented by the structural formula (2), φ is larger than an aromatic ring or a heterocyclic ring other than a benzene ring, for example, a benzene ring such as a naphthalene ring. And compounds having a structure.

The compound in which φ in the structural formula (1) is a benzene ring and o = 0 is a polyhydroxystyrene resin which is one of the existing resist materials.
Further, the compound in which φ shown in the structural formula (2) is a benzene ring, o = 1, and R ³ is a methyl group is a novolak resin which is one of the existing resist materials.

The compound represented by the structural formula (1) and the compound represented by the structural formula (2) have an increased ratio of carbon atoms and hydrogen atoms to the atoms constituting the polymer material as compared with the existing resist material. are doing.

In other words, in the above-mentioned polymer material constituting the resist layer, the ratio of oxygen atoms to the atoms constituting the polymer material is relatively small, so that the absorption of the entire polymer material in the extreme ultraviolet EUV wavelength region is possible. Is suppressed.

As described above, as a material constituting the resist layer, a polymer material having the above basic skeleton, a π-electron system of an aromatic ring in the existing resist material containing an aromatic ring, which is further expanded, and a structural formula By using at least one of the compound represented by (1) and the compound represented by Structural Formula (2), a polymer material having a low absorption coefficient at extreme ultraviolet wavelengths can be provided.

However, if the density of the entire resist material is significantly increased by increasing the proportion of carbon atoms or hydrogen atoms, the absorption coefficient at the extreme ultraviolet wavelength may be increased.

However, the inventors of the present invention have made various studies and found that the polymer material constituting the resist layer has a structure in which the π-electron system of the aromatic ring in the existing resist material containing an aromatic ring is further expanded. Of the compound represented by the formula (1) and the compound represented by the structural formula (2),
Even when at least one of them was used, it was found that the density of the entire resist material did not significantly increase, and it was possible to effectively utilize the decrease in the absorption coefficient at the extreme ultraviolet wavelength.

In the present invention, the polymer material constituting the resist layer has a linear absorption coefficient in the exposure wavelength range of 3.80 μm.
⁻¹ or less, more preferably 3.70 μ ⁻¹ or less.

When the linear absorption coefficient is 3.80 μ- ¹ or less, the transmittance of the resist layer is about 30 when the film thickness is 300 nm.
% Or higher. A linear absorption coefficient of 3.80 μ ⁻¹
When the transmittance exceeds this value, the irradiated light may not reach the lower portion of the resist layer sufficiently, and a good rectangular resist pattern may not be generated.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described.

Derivation of Theoretical Derivation of Linear Absorption Coefficient The present inventors have derived the theoretical absorption coefficient of a polymer material at a wavelength of 13 nm according to the method described below.

In deriving the theoretical value of the linear absorption coefficient of a polymer material at a wavelength of 13 nm, the wavelength 13
The absorption coefficient in nm and the density of the polymer material are required.

The absorption coefficient at a wavelength of 13 nm per atom is calculated from atomic data and Nuclear Tables (Henk
e, BL; Gullikson, EM; Davis, JC 1993, 54, 181).

With respect to PMMA (polymethyl methacrylate), the wavelength 1 obtained from this value and the experimental value of the density is used.
It is known that the linear absorption coefficient at 3 nm agrees very well with experimental values [J. Vac. Sci. Technol. B (Kubiak, G.
D .; Kneedler, EM; Hwang, RQ; Schulberg, MT; Ber
ger, KW; Bjorkholm, JE; Mansfield, WM 1992, 10, 25
93).

For predicting the density of the polymer material, Bicerano's theory was applied (Bicerano, J. Predictions of Propert).
ies of Polymers from their Structures, Marcel Dekk
er: New York, 1993).

This is a kind of graph theory, and is a technique for giving a correlation between the structure of a polymer and many physical properties. The error in the density of the polymer calculated by this method is 2.2% on average.
It is known that For this reason, the accuracy of the prediction of the linear absorption coefficient at a wavelength of 13 nm also has an error of 2.2% on average.

The actual calculation of the density used the module "Synthia" in the software "POLYMER" made by MSI of San Diego, USA. The computer used was a workstation "Oc" manufactured by Daikin Industries, Ltd.
tan ".

Example 1 When a polyhydroxystyrene resin was used as a polymer (existing resist material) as a basic skeleton and the π-electron system of the aromatic ring portion was expanded, specifically, the benzene ring portion was changed to a naphthalene ring. (Polyvinyl naphthol) was synthesized as shown below.

First, 100 g of 1-vinyl-4-acetoxynaphthalene and 5 g of azobisisobutyronitrile were added.
The reaction solution was dissolved in 00 ml of dehydrated tetrahydrofuran, and the reaction solution was sufficiently purged with argon.
Then, stirring was performed for 16 hours while maintaining this temperature.

Next, after allowing the reaction solution to cool to room temperature,
The polymer was poured into 5 liters of deionized water, and the white precipitate formed at this time was collected by filtration and dried to obtain a polymer of polyvinyl naphthalene.

The crude polymer was dispersed in 500 ml of methanol containing 20% of dimethylaminopyridine, and stirred at 45 ° C. to obtain a pale yellow homogeneous solution. This solution was poured into 10 liters of deionized water, and a white precipitate formed at this time was collected by filtration and reprecipitated from tetrahydrofuran / water to obtain 48 g of polyvinyl naphthol.

When a polyhydroxystyrene resin is used as a polymer (existing resist material) as a basic skeleton and the π-electron system of the aromatic ring is expanded, specifically, the benzene ring is replaced with an anthracene ring. A compound (polyvinylhydroxyanthracene) was synthesized as shown below.

First, 140 g of 9-vinyl-10-acetoxyanthracene and azobisisobutyronitrile were dissolved in 700 ml of dehydrated tetrahydrofuran.
After sufficiently purging the reaction solution with argon, the temperature was raised to 9
The temperature was adjusted to 0 ° C., and stirring was performed for 24 hours while maintaining this temperature.

Next, after allowing the reaction solution to cool to room temperature,
The polymer was poured into 5 liters of deionized water, and the white precipitate formed at this time was collected by filtration and dried to obtain a polymer of polyvinyl anthracene.

Then, this crude polymer was dispersed in 500 ml of methanol containing 20% of dimethylaminopyridine, and stirred at 45 ° C. to obtain a pale yellow homogeneous solution. The solution was poured into 10 liters of deionized water, and a white precipitate formed at this time was collected by filtration and reprecipitated from tetrahydrofuran / water to obtain 75 g of polyvinyl anthracene.

The linear absorption coefficient of polyvinyl naphthol (compound 2) and polyvinyl anthracene (compound 5) synthesized as described above was determined by calculation. Furthermore, when a polyhydroxystyrene resin (hereinafter referred to as Compound 1) is used as a polymer (existing resist material) serving as a basic skeleton and the π-electron system of the aromatic ring is expanded, specifically, the benzene ring is substituted. The linear absorption coefficient of the compound substituted with a naphthalene ring, an anthracene tube or a substituted anthracene ring was determined by calculation.

A polyhydroxystyrene resin (compound 1) serving as a basic skeleton and a compound 2 substituted with a naphthalene ring,
The structures of Compound 3 substituted with a methylnaphthalene ring, Compounds 4 and 5 substituted with an anthracene ring, and Compound 6 substituted with an ethylanthracene ring are as shown in the following Chemical Formula 5.

[0052]

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The linear absorption coefficient of each compound (wavelength 13n
Table 1 shows the calculation results of m).

[0054]

[Table 1]

As is clear from Table 1, by expanding the π-electron system of the aromatic ring of the existing resist material containing an aromatic ring, the linear absorption coefficient at a wavelength of 13 nm is reduced to 3.80 μ ^−1. It turns out that it becomes as follows. Particularly, compounds 3 in which the benzene ring of the polyhydroxystyrene resin is substituted with a methylnaphthalene ring, compounds 4 and 5 in which the anthracene ring is substituted, and compound 6 in which the ethylanthracene ring is substituted
Indicates that the linear absorption coefficient is 3.70 μ ⁻¹ or less.

Example 2 Polyhydroxystyrene resin is used as a polymer (existing resist material) as a basic skeleton, and in the compound represented by the structural formula (1), φ is a naphthalene ring and o = 0. The compound (polyvinyl naphthol) is a compound similar to the compound 2 prepared as described above.

Then, linear absorption coefficients of polyvinyl naphthol (compound 2), polyhydroxystyrene resin as a basic skeleton (compound 1), and various compounds represented by the structural formula (1) were obtained by calculation.

Polyhydroxystyrene resin (compound 1) serving as a basic skeleton, compound 2 in which φ is a naphthalene ring,
The structure of Compound 9, in which 7, 8, and φ are anthracene rings,
It is as shown in the following chemical formula 6.

[0059]

Embedded image

The linear absorption coefficient of each compound (wavelength 13n
Table 2 shows the calculation results of m).

[0061]

[Table 2]

As is apparent from Table 2, the use of the compound represented by the structural formula (1) as a resist material lowers the linear absorption coefficient at a wavelength of 13 nm to 3.80 μm.
It turns out that it becomes ^-1 or less. In particular, compounds 8 and 9 are:
It is understood that the linear absorption coefficient is 3.70 μ ⁻¹ or less.

Example 3 When a novolak resin was used as a polymer (existing resist material) as a basic skeleton and the π-electron system of the aromatic ring was expanded, specifically, the benzene ring was replaced with a naphthalene ring. The compound was synthesized as shown below.

First, 150 g of methyl naphthol was added to 3 g
75 g of a 7% aqueous formaldehyde solution and 0.1 ml of 35% concentrated hydrochloric acid were mixed, heated to 85 ° C., and stirred for 120 minutes.

Next, the reaction solution was allowed to cool to room temperature to precipitate the resin. Then, in order to wash the resin, the operation of adding pure water after tilting the upper layer of the solution was removed three times. After this operation, the resin in which the benzene ring portion of the novolak resin was substituted with a naphthalene ring was dried by drying the resin using a vacuum dryer in which the temperature of the apparatus was set to 85 ° C.
5 g were obtained.

The linear absorption coefficient of the resin (compound 12) synthesized as described above was determined by calculation. Also,
When a novolak resin (compound 10 or 11) is used as a polymer (existing resist material) serving as a basic skeleton and the π-electron system of the aromatic ring is expanded, specifically, the benzene ring is replaced with an anthracene ring The linear absorption coefficient at the time of the above was obtained by calculation.

A novolak resin (compound 1) serving as a basic skeleton
0,11), the compound 12 substituted with a naphthalene ring, and the compound 13 substituted with an anthracene ring are as shown in the following Chemical Formula 7.

[0068]

Embedded image

The linear absorption coefficient of each compound (wavelength 13n
Table 3 shows the calculation results of m).

[0070]

[Table 3]

As is apparent from Table 3, the linear absorption coefficient at a wavelength of 13 nm is reduced by further expanding the π-electron system of the aromatic ring of the existing resist material containing an aromatic ring. Further, it can be seen that any of the polymer materials in which the π-electron system of the aromatic ring is extended has a linear absorption coefficient of 3.70 μ ⁻¹ or less.

Example 4 A novolak resin was used as a polymer (existing resist material) as a basic skeleton. In the compound represented by the structural formula (2), φ represents a naphthalene ring, and o
= 1 and a compound in which R ³ is a methyl group was synthesized as shown below.

First, 150 g of methyl naphthol was added to 3 g
75 g of a 7% aqueous formaldehyde solution and 0.1 ml of 35% concentrated hydrochloric acid were mixed, heated to 85 ° C., and stirred for 120 minutes.

Next, the reaction solution was allowed to cool to room temperature to precipitate the resin. Then, in order to wash the resin, the operation of adding pure water after tilting the upper layer of the solution was removed three times. After this operation, the resin in which the benzene ring portion of the novolak resin was substituted with a naphthalene ring was dried by drying the resin using a vacuum dryer in which the temperature of the apparatus was set to 85 ° C.
5 g were obtained.

The resin (compound 1) synthesized as described above
4) was obtained by calculation. Further, a novolak resin (hereinafter referred to as compound 10) and a structural formula (2)
The linear absorption coefficients of the compounds represented by are determined by calculation.

A novolak resin serving as a basic skeleton (compound 1
0), the structure of compound 14 in which φ is a naphthalene ring and the structure of compound 15 in which φ is an anthracene ring are as shown in the following chemical formula 8.

[0077]

Embedded image

The linear absorption coefficient (wavelength 13n) of each compound
Table 4 shows the calculation results of m).

[0079]

[Table 4]

As is evident from Table 4, the use of the compound represented by the structural formula (2) as a resist material lowers the linear absorption coefficient at a wavelength of 13 nm.

Example 5 Acrylic resin (compound 16)
Is a polymer (existing resist material) as the basic skeleton, and when the π-electron system of the aromatic ring is expanded, specifically, the linear absorption coefficient when the benzene ring is replaced with an anthracene ring is calculated. I asked.

Acrylic resin (Compound 1) serving as a basic skeleton
6: poly (ethylphenyl methacrylate)) and the structure of compound 17 substituted with an anthracene ring are as shown in the following chemical formula 9.

[0083]

Embedded image

The linear absorption coefficient of each compound (wavelength 13n
Table 5 shows the calculation results of m).

[0085]

[Table 5]

As is apparent from Table 5, the linear absorption coefficient at a wavelength of 13 nm is reduced by further expanding the π-electron system of the aromatic ring of the existing resist material containing an aromatic ring. In addition, it can be seen that the compound 17 in which the π-electron system of the aromatic ring is extended has a linear absorption coefficient of 3.70 μ ⁻¹ or less.

As described above, the polymer material constituting the resist layer is a polymer material obtained by expanding the π-electron system of the aromatic ring in the existing resist material containing an aromatic ring, and represented by the structural formula (1). By using at least one of the compound and the compound represented by Structural Formula (2), it can be seen that the linear absorption coefficient of the existing resist material is reduced as compared with the linear absorption coefficient at a wavelength of 13 nm.

That is, as the polymer material, a polymer material obtained by further expanding the π-electron system of the aromatic ring in the existing resist material containing an aromatic ring, the compound represented by the structural formula (1), and the structural formula (2) At least one of the compounds shown in
By using one, a more suitable resist material with high transparency can be obtained.

In the above embodiments, polyhydroxystyrene resin, novolak resin, and acrylic resin have been described as examples of the polymer. However, the present invention is not limited to this. A polymer, a silane-based polymer, a vinyl-based polymer, a polyimide-based polymer, a fluorine-based polymer, and the like can also be applied to a polymer containing an aromatic ring.

Further, the extension of the π-electron system of the aromatic ring is not limited to the embodiment, but may be any substitution that further extends the π-electron system, such as a substituted pyrene ring, a substituted pyridine ring, and a substituted pyran. A ring, a substituted pyrazine ring, a substituted pyrrole ring, or the like may be used.

In the above examples, the substituents R ¹ , R ² , R ³ , R ⁴ , R ^{5 in} the structural formula (1) and the substituents R ¹ , R ² , As R ³ and R ⁴ , a hydrogen atom, a methyl group, or a butyl group has been described as an example, but the present invention is not limited thereto, and an alkyl group, a substituted alkyl group, a phenyl group, a substituted phenyl group, Ether group, substituted ether group, ester group,
You may use a substituted ester group, a halogen atom, etc.

[0092]

As is clear from the above description, in the present invention, the polymer material constituting the resist layer is obtained by further expanding the π electron system of the aromatic ring in the existing resist material containing an aromatic ring. Since at least one of a polymer material, a compound represented by Structural Formula (1), and a compound represented by Structural Formula (2), which has an increased light transmittance in a wavelength region of extreme ultraviolet light, is used, the wavelength of extreme ultraviolet light is used. The light transmittance in the region is increased. Therefore, by using this polymer material for the resist layer, a resist pattern having a better shape can be obtained, and ultrafine processing can be performed more than ever.

In the extreme ultraviolet (EUV) lithography process, by using a polymer material having high transparency, it is possible to increase the thickness of the resist layer and to improve the etching resistance of the resist layer. Can be.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 21/30 531E (72) Inventor Ei Yano 4-1-1 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu F term in reference (reference) 2H025 AA02 AA03 AA09 AB16 AC03 AC05 AD01 AD03 CB14 CB17 CB29 CB41 CB51 5F046 AA07 AA08 CA08

Claims (4)

[Claims] 1. An exposure method for selectively exposing a resist layer to one of X-rays, vacuum ultraviolet rays, extreme ultraviolet rays and soft X-rays to pattern the resist layer into a predetermined shape, wherein the polymer material constituting the resist layer is A polymer material obtained by further expanding the π-electron system of an aromatic ring in an existing resist material containing an aromatic ring, a compound represented by the following formula 1,
And at least one of the compounds represented by the following chemical formula 2.
Exposure method characterized by using one. Embedded image Embedded image 2. The exposure method according to claim 1, wherein a linear absorption coefficient of the polymer material constituting the resist layer in an exposure wavelength range is 3.80 μ ⁻¹ or less. 3. The exposure method according to claim 1, wherein said exposure wavelength is 7 nm to 16 nm. 4. The exposure method according to claim 1, wherein said exposure is exposure by reduction projection using a reduction projection optical system.