JP2748738B2 - α- [o- (methoxy) styryl] -N-phenylnitrone 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 a wall which is closer to the vertical as the contrast of the exposed image is larger. However, when performing very high resolution exposure,
There is a problem that the contrast of the exposed image is reduced and a clear resist image cannot be obtained.

In order to improve the resolution and 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. Sho 62-40697). −234148
A method of forming a resist pattern using the method disclosed in Japanese Patent Application Laid-Open No. H10-260,045) has been proposed. Further, in order to improve the resolution, the NA of the stepper lens has been increased (NA: numerical aperture of the lens). However, when the NA is increased, the resolution is improved, but the depth of focus cannot be increased, and therefore, there is a disadvantage that it is difficult to form a fine resist pattern.

As a means for solving the above problems and forming a fine resist pattern, it is preferable to make the photobleachable layer for contrast enhancement thinner. A photobleachable layer having a high optical density and a low transparency rate is indispensable. Accordingly, a photobleachable material having a high optical density and a low transparency rate (CEM:
Contrast Enhanced Materialia
Although ls) is useful, any of the conventional ones are hardly satisfactory. Therefore, a nitrone compound useful as a main component of such a photobleachable material is required.

[0005] The present invention has been made in view of the above circumstances,
A novel nitrone compound useful as a main component of a photobleaching material for enhancing contrast, which has a high optical density and a low transparency rate and enables formation of a fine resist pattern, and a photobleaching property containing the nitrone compound The purpose is to provide the material.

[0006]

The present inventors have made intensive studies to achieve the above object. As a result, for example, after hydrogenation of nitrobenzene, 2-methoxycinnamaldehyde is reacted with the hydrogenation. Α- [o- (methoxy) styryl] -N-phenylnitrone represented by the following formula (1), which can be synthesized, is useful as a main component of a photobleaching material for enhancing contrast, and particularly has a wavelength of 36.
It has been found that it can be very effective in contrast-enhanced lithography with 5 nm light (i-line).

[0007]

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That is, the novel nitrone compound of the above formula (1) has photobleaching property for i-line, and has an optical density of about 1.3 to 1.5 times that of the known nitrone compound for i-line. And the transparency rate is as slow as two-thirds or less, and the depth of focus is improved more than twice, unpredictably. Therefore, the photobleaching is performed using the nitrone compound of the formula (1). It has been found that a fine resist pattern can be formed with high contrast, high resolution, and high accuracy by preparing a conductive material and performing i-line contrast enhancement lithography using a stepper lens with a high NA. The present invention has been accomplished.

Now, the present invention will be described in further detail. The novel nitrone compound of the present invention is α- [o- (methoxy) styryl] -N-phenylnitrone represented by the following formula (1). The compound has a high optical density at i-line and a low rate of transparency,
It is a thin film of about μm (it is conventionally about 0.5 μm) and has a photobleaching effect.

[0010]

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The nitrone compound of the above formula (1) is a yellow crystal having a melting point of 121 to 122 ° C. and room temperature.

The α- [o- (methoxy) styryl] -N-phenylnitrone of the formula (1) of the present invention is obtained by, for example, hydrogenating nitrobenzene and then adding 2- It can be synthesized by reacting methoxycinnamaldehyde.

[0013]

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In this case, the above reaction is preferably performed in an organic solvent such as methanol.

In addition, hydrogenation of nitrobenzene is performed by adding 1.7 to 2.3 equivalents of hydrogen to nitrobenzene to 1 to 1.
It can be filled at a pressure of 10 kg / cm ² and carried out at room temperature in the presence of a catalytic amount of a catalyst such as platinum on carbon.

Further, when reacting 2-methoxycinnamaldehyde with hydrogenated nitrobenzene, 2-methoxycinnamaldehyde is added at a ratio of 0.8 to 1.2 mol per mol of nitrobenzene, and acid such as acetic acid is added. It is desirable to carry out in the presence of The reaction conditions are 20 to
It is preferable to set the temperature at 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 α- [o- (methoxy) styryl] -N-phenylnitrone of the formula (1).

The photobleachable material of the present invention comprises the above α- [o-
(Methoxy) styryl] -N-phenylnitrone, which may be used alone, and the nitrone compound and the binder are dissolved in an organic solvent and mixed, and the photobleaching property capable of spin casting is used. It can also be used as a 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 nitrone compound 1
A mixture of about 30 parts, preferably 1 to 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, and a mixture of an aromatic hydrocarbon and an alcohol such as propanol and butanol are exemplified.

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 Copolymers, hydrocarbon-soluble cellulose ethers and cellulose esters, polyvinylpyrrolidone homopolymers and copolymers, and polyvinyl alcohols and pullulans into which triorganosilyl groups have been introduced are exemplified.

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.

A resist pattern using the photobleachable material of the present invention can be formed 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 photo-bleaching material of the present invention is applied on the photoresist layer 2 by a method such as spin coating to form a photo-bleaching layer. The layer 3 is formed, and the photobleachable layer 3 is exposed to ultraviolet rays 4 having 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 development is performed. The resist pattern 5 can be formed by a method of developing using a liquid.

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 examples shown in FIGS. 1 and 2, the portion B remains as a resist pattern 5 because a positive resist is used as the photoresist layer 2, but the photoresist has a predetermined level of contrast 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 threshold value.

[0024]

The α- [o- (methoxy) styryl] -N-phenylnitrone of the above formula (1) of the present invention is particularly useful for i
Since the optical density of the line is large and the speed of transparency is slow, a photobleaching material that has a photobleaching effect with a thin film of about 0.1 μm and can form a fine resist pattern with high contrast, high resolution and high precision Therefore, it is useful as a main component of a photobleachable material for enhancing contrast that enables formation of a fine resist pattern.

[0025]

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 In a 1-liter autoclave, 90.0 g (731 mmol) of nitrobenzene, 11.3 g of dimethyl sulfoxide, and 29% aqueous ammonia 5.
0 g, 2.0 g of 5% platinum-supported catalyst, 260 g of methanol
Was added, and the system was charged with hydrogen at a pressure of about 4 kg / cm ² and stirred at room temperature until 2 equivalents of hydrogen had reacted with nitrobenzene. Thereafter, 109.8 g (677 mmol) of 2-methoxycinnamaldehyde, acetic acid 3
0.0 g and 400 g of methanol were added, and the mixture was stirred at room temperature for 5 hours. After the reaction mixture was filtered to remove the catalyst, 600 g of toluene and 600 g of water were added, and the toluene layer was extracted. 600 g of a saturated aqueous solution of sodium hydrogencarbonate was added thereto to obtain a toluene layer after neutralization, and the mixture was concentrated under reduced pressure to about 200 g. Approximately 100 g of hexane was added to the concentrated solution to carry out recrystallization, and red crystals were obtained. When dried, the yield was 107.0 g (62.4% yield), α-purity 96% pure
[O- (Methoxy) styryl] -N-phenylnitrone was isolated. The mass spectrum of the obtained α- [o- (methoxy) styryl] -N-phenylnitrone (M
S), nuclear magnetic resonance spectrum (NMR), infrared spectrum (IR) and elemental analysis (CHN) are shown below. MS: m / e (spectral intensity ratio) 253 (53), 237 (11), 236 (18), 2
06 (65), 146 (35), 91 (54), 77
(100), 51 (35)

[0027]

Embedded image(A) 6.8-8.0 multiplet 12H (b) 3.89 singlet 3H IR: (cm^-1) 3080, 2940, 2840, 1595, 1540,
1490, 1470, 1390, 1250, 1055
760 CHN: (%) C₁₆H_FifteenN O_Two Theoretical value C: 75.87 H: 5.97 N: 5.53 Actual value C: 75.65 H: 6.02 N: 5.81

Example 2 α- [o as a photobleachable material
-(Methoxy) styryl] -N-phenylnitrone and a 2.5% solution of polyvinylpyrrolidone-vinyl acetate copolymer having a molecular weight of about 3,000 and a component ratio of 6: 4 in ethylbenzene-1-butanol (weight ratio 1: Using the mixture of 1), a 5% aqueous solution of polyvinyl alcohol having a molecular weight of about 10,000 was used as an intervening layer, and a resist pattern was formed according to the lithography process shown in FIG. First, KTI-895i was added to the substrate 1 made of a silicon wafer.
(Positive resist, manufactured by KTI) 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). Further, the photobleachable material was spin-coated thereon to form a photobleachable layer 7 (FIG. 2C), and the portion A was selectively exposed to ultraviolet light 4 of 365 nm by a 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. 2E). The obtained resist pattern had a 0.35 μm resolution in which the contrast was enhanced and the depth of focus was improved twice or more.

[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

Claims (2)

(57) [Claims] 1. α- [o- (methoxy) styryl] -N-phenylnitrone represented by the following formula (1). Embedded image 2. The α- [o- (methoxy) according to claim 1.
[Styryl] -N-phenylnitrone.