JP2757640B2 - α- [p- (dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound and photobleachable material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel photobleaching material suitable as a main component of a photobleachable material for enhancing the contrast of an image of a subject, such as a photolithography process mask in the manufacture of semiconductor integrated circuits. The present invention relates to a nitrone compound and a photobleachable material containing the nitrone compound.

[0002]

2. Description of the Related Art In a lithography technique, a photoresist image formed by exposing and developing a photoresist to a desired pattern shape has a shape having walls that are closer to vertical as the contrast of the exposed image is larger. However, when performing exposure with a very high resolution, there is a problem that the contrast of the exposed image is reduced and a clear resist image cannot be obtained.

Therefore, as a method for achieving resolution and resolution of a pattern shape, a photobleachable layer for enhancing contrast having a maximum absorption for light having a wavelength of 300 to 450 nm (Japanese Patent Publication No. 62-40697, Japanese Patent Application Laid-Open No. 62-234148
A resist pattern forming method using the above method has been proposed, and a nitrone compound which is a main component of the photobleachable material has the following structure.

[0004]

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However, the nitrone compound, which is the main component of the photobleachable material, is not satisfactory in compatibility with the resin used as a binder in the photobleachable material.
Therefore, if the photobleachable material is spin-coated on a photoresist and left for 12 hours or more, the nitrone compound crystallizes. As described above, since a defect occurs in the coating film in the portion where the nitrone compound has been crystallized, a fine resist pattern cannot be obtained, and the yield does not increase. Therefore,
It has extremely good compatibility with a resin as a binder, and has a photo-bleachable material (CEM: Contrast Enhanc).
There is a need for a nitrone compound useful as a main component of ed Materials.

The present invention has been made in view of the above circumstances,
A novel nitrone compound useful as a main component of a photobleachable material for contrast enhancement that has excellent compatibility with a resin and enables formation of a fine resist pattern at a high yield, and a photobleachable material containing the nitrone compound The purpose is to provide.

[0007]

The present inventors have made intensive studies to achieve the above object, and as a result, for example, after hydrogenating an alkylnitrobenzene represented by the following general formula (2), 4- represented by the following formula (3)
Α- [p- represented by the following general formula (1), which can be synthesized by reacting dimethylaminobenzaldehyde.
(Dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound is useful as a main component of a photobleaching material for enhancing contrast, and has a great power particularly in contrast-enhancing lithography with light (i-line) having a wavelength of 365 nm. I found something that could work.

[0008]

Embedded image (Wherein, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same or different alkyl groups or hydrogen atoms, respectively, and at least one is an alkyl group)

That is, the novel nitrone compound of the above formula (1) has a photobleaching property, particularly for i-ray, and is more compatible with a resin as a binder of a photobleachable material than a known nitrone compound. Is very good, and even if left after spin-coating on a photoresist, crystallization of the nitrone compound, that is, no film defect occurs, so that a fine resist pattern can be formed and the yield is improved. Therefore, when a photobleachable material is prepared using the nitrone compound of the formula (1) and contrast-enhanced lithography using i-line is performed, a fine resist pattern with high contrast, high resolution, and high precision is formed at a high yield. The inventors have found that the present invention can be performed, and have accomplished the present invention.

Now, the present invention will be described in further detail. The novel nitrone compound of the present invention has the following general formula (1)
Α- [p- (dimethylamino) phenyl]-represented by
It is an N- (alkylphenyl) nitrone compound.

[0011]

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Here, R ¹ , R ² ,
R ³ , R ⁴ and R ⁵ are the same or different alkyl groups or hydrogen atoms, respectively, and at least one is an alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a tert group.
Those having 1 to 8 carbon atoms, such as -butyl group and cyclohexyl group, are preferable, and among them, methyl group, ethyl group, propyl group and butyl group are more preferably used.

Specific examples of the nitrone compound of the formula (1) include α- [p- (dimethylamino) phenyl] -N- (2,3-dimethylphenyl) nitrone and α
-[P- (dimethylamino) phenyl] -N- (2,6
-Dimethylphenyl) nitrone, α- [p- (dimethylamino) phenyl] -N- (2-methylphenyl) nitrone, α- [p- (dimethylamino) phenyl] -N-
(4-methylphenyl) nitrone, α- [p- (dimethylamino) phenyl] -N- (4-ethylphenyl) nitrone, α- [p- (dimethylamino) phenyl] -N
-(4-isopropylphenyl) nitrone and the like are exemplified.

The α- [p- (dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound of the formula (1) of the present invention is an industrially available alkyl compound represented by the following general formula (2). Using nitrobenzene as a raw material, the compound is synthesized by hydrogenating an alkylnitrobenzene of the formula (2) as shown in the following reaction formula and then reacting it with 4-dimethylaminobenzaldehyde of the formula (3). Can be.

[0015]

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In this case, the above reaction is preferably performed in an organic solvent such as methanol. The hydrogenation of the alkylnitrobenzene of the formula (2) is performed by adding 1.7 to 2.3 equivalents of hydrogen to the alkylnitrobenzene for 1 to 10 k.
The reaction can be performed at room temperature in the presence of a catalyst such as platinum on carbon in a catalytic amount by filling at a pressure of g / cm ² .

Further, when 4-dimethylaminobenzaldehyde is reacted with hydrogenated alkylnitrobenzene, 4-dimethylaminobenzaldehyde is added at a ratio of 0.8 to 1.2 mol per mol of alkylnitrobenzene, and acetic acid or the like is added. It is desirable to carry out in the presence of an acid. The reaction conditions are preferably at 20 to 50 ° C. for 3 to 8 hours. After completion of the reaction, the solvent layer is neutralized and concentrated, and then recrystallized to obtain the desired (1).
Α- [p- (dimethylamino) phenyl] -N-
An (alkylphenyl) nitrone compound can be obtained.

The photobleachable material of the present invention has the above α- [p-
(Dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound, which may be used alone, or a mixture of this nitrone compound and a binder dissolved in an organic solvent and mixed. It can also be used as a moldable photobleachable material. This mixture comprises (A) 100 parts of an organic solvent (parts by weight, the same applies hereinafter), (B) 0 to 30 parts, preferably 0 to 15 parts, of an inert organic polymer binder, and (C) the above nitrone compound 1 to 1. 30 parts, preferably 1
What mixed about 15 parts is suitable.

Here, the solvent of the component (A) includes aromatic hydrocarbons such as toluene, xylene and ethylbenzene;
A mixture of an aromatic hydrocarbon and an aliphatic hydrocarbon such as cyclohexane, a mixture of an aromatic hydrocarbon and an alcohol such as propanol and butanol, and the like can be given.

As the binder of the component (B), a vinyl acetate homopolymer or copolymer or a partially saponified product thereof, a copolymer of styrene or a derivative thereof, a homopolymer of acrylic acid or methacrylic acid ester or Examples thereof include copolymers, hydrocarbon-soluble cellulose ethers and cellulose esters, homopolymers or copolymers of polyvinylpyrrolidone, and polyvinyl alcohols and pullulans into which triorganosilyl groups have been introduced.

When the above components (A), (B), and (C) are mixed, it is possible to dissolve each of the components (B) and (C) in the component (A) to form a solution. preferable.

The formation of a resist pattern using the photobleachable material of the present invention can be performed by the lithography process shown in FIGS. FIG. 1 shows an example in which a photobleachable layer is directly formed on a photoresist layer. First,
A photoresist layer 2 is formed on a substrate 1 such as a silicon wafer by a method such as spin coating, and the photobleachable material of the present invention is applied on the photoresist layer 2 by a method such as spin coating to form a photobleachable layer 3. Is formed, and the photobleachable layer 3 is exposed to ultraviolet light 4 of a predetermined wavelength in a desired pattern shape by a reduced projection method, that is, the portion A in FIG. 1 is exposed, the photobleachable layer 3 is removed, and the developer is removed. The resist pattern 5 can be formed by a developing method using the resist pattern 5.

FIG. 2 shows an example in which a thin intervening layer 6 made of a neutral substance such as polyvinyl alcohol is provided between the photobleachable layer and the photoresist layer in order to isolate the photobleachable layer from the photoresist layer.

In the example shown in FIG. 1 and FIG. 2, the portion B remains as the resist pattern 5 because a positive type resist is used as the photoresist layer 2, but the photoresist has a predetermined level with respect to light of a predetermined wavelength. Either a positive type or a negative type can be used as long as it shows a contrast threshold value.

[0025]

According to the present invention, α- [p- (dimethylamino) phenyl] -N- (alkylphenyl) of the above formula (1) is used.
The nitrone compound has a photobleaching property particularly for i-rays,
And it is possible to provide a photobleachable material which has good compatibility with a resin as a binder of the photobleachable material, and which can form a fine resist pattern with high contrast, high resolution, high precision and high yield, Therefore, it is useful as a main component of a photobleachable material for enhancing contrast that enables formation of a fine resist pattern.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

Example 1 A 1-liter autoclave was charged with 110.5 g (731 mm) of 2-nitro-m-xylene.
ol), 11.3 g of dimethylsulfoxide, 5.0 g of 29% aqueous ammonia, 4.0 g of a 5% platinum-supported catalyst, and 260 g of methanol, and about 4 kg / cm ² of hydrogen was added to the system.
And stirred at room temperature until the equivalent of hydrogen to 2-nitro-m-xylene had reacted. Then, 101.0 g of 4-dimethylaminobenzaldehyde was further added.
(677 mmol), acetic acid 30.0 g, methanol 10
0 g was added, and the mixture was stirred at room temperature for 8 hours. After filtering the reaction mixture and removing the catalyst, 600 g of toluene and 600 g of water were used.
Was added, and the toluene layer was extracted. To this was added 600 g of a saturated aqueous solution of sodium hydrogen carbonate, and after neutralization, a toluene layer was obtained and concentrated under reduced pressure to about 500 g. About 500 g of hexane was added to the concentrated liquid to carry out recrystallization to obtain yellow crystals, which were dried to obtain 30.7 g (yield: 16.9).
%), 98% pure α- [p- (dimethylamino) phenyl] -N- (2,6-dimethylphenyl) nitrone.

The obtained α- [p- (dimethylamino) phenyl] -N- (2,6-dimethylphenyl) nitrone has a mass spectrum (MS) and a nuclear magnetic resonance spectrum (N
MR), infrared spectrum (IR), and elemental analysis results are shown below.

< MS: m / e (spectral intensity ratio)> 2
68 (100), 252 (33), 251 (41), 1
49 (49), 121 (45)

[0030]

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<IR: (cm ⁻¹ )> 3095, 305
1, 2958, 2918, 2810, 1605, 152
2, 1470, 1446, 1396, 1362, 119
8, 1169, 1126, 1099, 1059, 94
7,889,850,816

<Elemental analysis value: (%) C ₁₇ H ₂₀ N ₂ O> Theoretical value C: 76.1 H: 7.5 N:
10.4 Observed value C: 76.3 H: 7.5 N:
10.5

Example 2 Example 1 as a photobleachable material
Α- [p- (dimethylamino) phenyl]-obtained in
N- (2,6-dimethylphenyl) nitrone and polyvinylpyrrolidone having a molecular weight of about 3,000 and a component ratio of 6: 4
Using a mixture of each 3.0% ethylbenzene-1-butanol solution (weight ratio 1: 1) of the vinyl acetate copolymer, and using a 5% aqueous solution of polyvinyl alcohol having a molecular weight of about 10,000 as an intervening layer, FIG. A resist pattern was formed according to the lithography process shown. First, the KTI-895i (KT
A positive resist (manufactured by Company I) is spin-coated to form a resist layer 2 (FIG. 2A), and then the above-described intervening layer 6 is spin-coated on the resist layer 2 (FIG. 2B). The photobleachable material is further spin-coated thereon to form a photobleachable layer 7.
Was formed (FIG. 2C). I left it for more than 12 hours,
Since no defects were found in the coating film, portion A was selectively exposed to ultraviolet light 4 of 365 nm by the reduced projection method (FIG. 2 (d)). Thereafter, the intervening layer 6 and the photobleachable layer 7 were simultaneously removed using pure water, and development was performed using an alkaline developer to form a resist pattern 5 (FIG. 2).
(E)). The obtained resist pattern had a 0.40 μm resolution with enhanced contrast.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a lithography process using a photobleachable material of the present invention.

FIG. 2 is a process chart showing another example of a lithography process using the photobleachable material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Photoresist layer 3 Photobleachable layer 4 Ultraviolet light 5 Resist pattern 6 Intermediate layer 7 Photobleachable layer

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Ito 28-1, Nishifukushima, Oku-ku, Nakatsugi-gun, Niigata Pref. , 3141-3144 (58) Fields surveyed (Int. Cl. ⁶ , DB name) C07C 291/02 G03C 1/675 G03F 7/004 507 G03F 7/004 531 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. α- [p- represented by the following general formula (1)
(Dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound. Embedded image (Wherein, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same or different alkyl groups or hydrogen atoms, respectively, and at least one is an alkyl group) 2. A photobleachable material comprising the α- [p- (dimethylamino) phenyl] -N- (alkylphenyl) nitrone compound according to claim 1.