JP2746413B2 - Photoresist composition for deep ultraviolet light - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel photoresist composition for far-ultraviolet light, and more particularly, to a far-ultraviolet light of 313 nm or less, particularly 2
This is suitable for the case where light using a KrF excimer laser of 48 nm as a light source is used.

<Conventional Technology> In recent years, the manufacturing technology of semiconductor elements and integrated circuits has been remarkably advanced, and accordingly, the requirements for photolithography technology have been increasing year by year. In particular, the resolution R of the resist in the reduced projection exposure method is represented by the Rayleigh equation R = kλ / NA
As a method of improving the resolution, the numerical aperture of the lens represented by NA is increased, the wavelength (λ) of the exposure light is shortened, and k determined by the resist process is reduced. There are three ways to do this. Hitherto, the improvement of the resolution has mainly depended on the increase in the NA of the stepper and the improvement of the resist process. However, increasing the NA of a stepper requires a DOF expressed by the following equation (DO
F), Problem arises.

In contrast, shortening the wavelength λ has a smaller effect on the depth of focus than NA, and in recent years, excimer lasers with shorter wavelengths, especially g-lines (436 nm) of conventional high-pressure mercury lamps, have been used as light sources. KrF excimer laser light (248
nm) or XeCl excimer laser (308 nm) is being developed.

By the way, conventional g-line (436 nm) or i-line (365 nm)
nm) as a light source, a photoresist comprising an alkali-soluble novolak resin and naphthoquinonediazidesulfonic acid ester is used. These photoresists have the property of being transparent when exposed to g-rays (436 nm) and i-rays (365 nm), so that high-resolution patterns can be obtained.

Currently, DRAMs (Dynamic Random Access Memory) that are mass-produced are mainly 1M bits using the above-mentioned photoresist, but increasing the capacity of semiconductor memories is proceeding at a faster-than-expected rate. In recent years, a high resolution resist, especially a 16 Mbit DRAM, has been required.

<Problems to be Solved by the Invention> However, the photoresist comprising the alkali-soluble novolak resin and the naphthoquinonediazide sulfonic acid ester described above has a line width when g-line is used.
Since the limit is up to about 0.5 μm, when trying to form a fine pattern using far ultraviolet light of 313 nm or less as a light source that can improve the resolution, the resist strongly absorbs the far ultraviolet light, and the bottom of the resist film Light does not reach
The problem of giving an overcut profile arises.

On the other hand, poly (methyl methacrylate) or the like, which becomes a transparent resist material with far ultraviolet light, has a problem that it does not have dry etching resistance.

In view of the circumstances described above, the present invention is a deep ultraviolet light which is alkali-developable and has excellent characteristics such as high transparency and dry etching resistance at 248 nm, which is a KrF excimer laser light, particularly at a deep ultraviolet light of 313 nm or less. An object is to provide a photoresist composition for light.

<Means for Solving the Problems> The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a photoresist composition comprising a copolymer having a styrene / maleimide structure and a photosensitizer has been developed by alkali development. Possible, high transparency in far ultraviolet light of 313nm or less,
Further, they have found that they are remarkably excellent in dry etching resistance and the like, and completed the present invention based on this finding.

The photoresist composition for far ultraviolet light according to the present invention based on such knowledge comprises a copolymer having a repeating unit represented by the following general formula and a photosensitizer, and is used for far ultraviolet light exposure at 313 nm or less. And

In the formula, R ₁ represents hydrogen or a methyl group, R ₂ represents an alkyl group, an aralkyl group, R ₃ represents a hydrogen, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group;
And n ₁ , n ₂ , n ₃ , n ₄ and n ₅ represent mol% of each repeating unit, and each is in the following range. n ₁ = 25-8
0, n ₂ = 10 to 70, n ₃ = 0 to 40, n ₄ = 0 to 40, n ₅ = 0 to 10 The copolymer according to the present invention having the repeating unit represented by the general formula (1) is used. The photoresist composition for far ultraviolet light to be used (hereinafter referred to as “photoresist composition”) is as follows.
KrF excimer laser light has a high transmittance at 248 nm, has a high resolution resist pattern and has the characteristics of high dry etching resistance.Based on this, it is useful for lithography using deep ultraviolet light exposure. That is, the present inventors have found for the first time.

The copolymer having a repeating unit represented by the general formula (1) used as a binder resin in the photoresist composition of the present invention and a copolymer having a similar structure are disclosed in JP-A-61-1986. It is disclosed in Japanese Patent No. 162039. However, a photoresist composition using such a copolymer disclosed in the known literature, 25% after development.
It only discloses that it can withstand high temperature treatment at 0 ° C,
No consideration is given to transparency to far ultraviolet light of 13 nm or less, or resistance to dry etching.

 Hereinafter, the present invention will be described in detail.

As the binder resin of the photoresist composition of the present invention, a copolymer having a repeating unit represented by the above general formula (1) is used, wherein R ₁ represents hydrogen or a methyl group, and R ₂ represents Alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclopentyl group and cyclohexyl group, carboxymethyl group, carboxyethyl group, carboxypropyl group, carboxybutyl group, methoxymethyl group, Represents a substituted alkyl group such as a methoxyethyl group, an aralkyl group such as a benzyl group or a phenylethyl group, and R ₃ represents a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopentyl group, a cyclohexyl group, etc. Alkyl, allyl, butenyl and other alkenyl, phenyl, Conversion phenyl group, an aryl group such as a naphthyl group. m represents an integer of 1 to 6, where m is 0, that is, the N-hydroxyphenylmaleimide unit has poor transparency to far ultraviolet light. When m is 6 or more, the dry etching resistance decreases. n _{1 to} n ₅ represent mol% of each repeating unit, and this range is characteristic of the photoresist composition of the present invention.
Good transparency to far ultraviolet light, especially KrF-excimer laser light of 248 nm, high dry etching resistance,
It is determined so as to satisfy the conditions such as high heat resistance, alkali developing, no swelling and good resolution.
Transparency, dry etching resistance, heat resistance, alkali developability, swelling, etc. are determined by the following factors. Alkaline developability is provided by phenol and carboxyl groups, but phenol has a strong absorption in the deep ultraviolet region, which adversely affects transparency. Let it. The dry etching resistance is better as the benzene nucleus density is higher, but the benzene nucleus absorbs in the far ultraviolet region. Further, the imide structure contributes to heat resistance, which also has an absorption in the far ultraviolet region. For this reason, the range of n ₁ ~n ₅ is follows. n ₁ = 25 to 80, n ₂ = 10 to 70, n ₃ = 0 to 40, n ₄ = 0 to 4
0, n ₅ = 0~10, more _{preferably, n 1 = 40~70, n 2} = 20~6
0, n ₃ = 0 to 30, n ₄ = 0 to 30, and n ₅ = 0 to ₅ .

The copolymer having a repeating unit represented by the general formula (1) is, for example, a copolymer obtained by copolymerizing maleic anhydride and styrene or α-methylstyrene with the following general formula (2) And optionally an amine represented by R ₂ —NH ₂ (R ₂ has the same meaning as described above) and / or
Alternatively, it can be produced by reacting an alcohol represented by R ₃ —OH (R ₃ has the same meaning as described above) with a part or all of the maleic anhydride component, and performing a cyclization dehydration reaction.

As the photosensitive agent in the photoresist composition of the present invention, any compound having sensitivity to active radiation can be used. Examples of such a photosensitizer include a naphthoquinonediazide compound, a compound represented by the following general formula (3), Where R ₄ is And R ₅ represents an alkyl group, an alkoxyl group, an alkylamino group, or an aryl group. R ₆ represents an alkyl group, an alkoxyl group, an alkylamino group or an aryl group, R ₇ represents an alkyl group or an aryl group, and R ₈ and R ₉ represent an alkyl group, an aryl group, an aralkyl group, an alkoxyl group or an aryloxyl group. Express.

 Alternatively, an aromatic azide compound is suitably used.

The naphthoquinonediazide compound is a reaction product of 1,2-naphthoquinonediazide-4-sulfonyl chloride or 1,2-naphthoquinonediazide-5-sulfonyl chloride with a compound having a hydroxyl group or an amino group, that is, a sulfonic ester, a sulfonamide And the like. Examples of the compound having a hydroxyl group include alcohols such as butanol, methyl cellosolve, ethyl cellosolve, and polyethylene glycol, or phenol, chlorophenol, cresol, isopropylphenol, xylenol, p-cyclopentylphenol, p-cyclohexylphenol, and hydroxybenzoic acid. Ester, alkoxyphenol, dialkoxyphenol, hydroquinone, pyrocatechol, resorcinol, dihydroxybenzoate, bisphenol A, bis (hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, bis (hydroxyphenyl) ) Sulfone, trihydroxybenzoate, trihydroxybenzene, trihydroxybenzophenone, tetrahydro Shi benzophenone, trihydroxy biphenyl, can be exemplified compounds having a phenolic hydroxyl group, such as tri-hydroxybiphenyl ether. Examples of the compound having an amino group include aniline and β-aminodiphenylamine. Among these naphthoquinonediazide compounds, 1,2-naphthoquinonediazide-4-sulfonic acid esters or amides are more preferable because the transmittance at 248 nm increases upon exposure.

Said α- Ketojiazo compound represented by the general formula (3), for example, Chem.Ber. 94, 929 (1961) , Chem.Ber., 102, 2
216 (1969), Chem. Ber., 103 , 1477 (1970), Proc. Of S
It can be produced by a known method described in PIE, 771 , 2 (1987), US Pat, 4,626,491 (1986), JP-A-61-240237, JP-A-61-223837, and the like. Specific examples of these compounds include 2,2-dimethyl-4,6-
Diketo-5-diazo-1,3-dioxane, 2-methyl-2
-Heptyl-4,6-diketo-5-diazo-1,3-dioxane, (diazophenacyl) -diphenylphosphine oxide, (diazo-pt-butylphenacyl) diphenylphosphine oxide, (diazo-p-methoxyphenacyl) diphenyl Phosphine oxide, (diazophenacyl) dimethylphosphonate, diphenylphosphinyldiethylcarbamoyldiazomethane, diphenylphosphinylethoxycarbonyldiazomethane, diphenylphosphinylcyclohexyloxycarbonyldiazomethane, β-tolylsulfonyl N, N-diethylcarbamoyldiazomethane, β- Tolylsulfonylethoxycarbonyldiazomethane, phenylsulfonylbenzoyldiazomethane, trans-2-diazodecalin-1,3
-Dione, ethyl 3-diazo-2,4-dioxodecalin carboxylate, ethyl 5-diazo-2,2-dimethyl-4,6-dioxocyclohexanecarboxylate, 2
-Diazo-5,5-pentamethylenecyclohexane-1,3-
And oligomers of dione, 2-diazomalonate.

Among the compounds represented by the general formula (3), R ₄
But In particular, compounds in which R ₅ is an alkoxy group or an alkylamino group are particularly preferable because the exposure increases the transmittance at deep ultraviolet light, particularly at 248 nm.

Specific examples of the aromatic azide compound include azidobenzene, azidoanisole, azidonitrobenzene, azidodimethylaniline, diazidebenzophenone, diazidediphenylmethane, diazidediphenylether, diazidediphenylsulfone, diazidophenylisulphide, and the like.
Diazidostilbene, azidochalcone, diazidochalcone, diazidobenzalacetone, 2,6-di (azidobenzal) cyclohexanone, 2,6-di (azidobenzal) -4
-Methylcyclohexanone, 3- (4- (p-azidophenyl) -1,3-butadienyl) -5,5-dimethyl-2-cyclohexane-1-one and the like.

The mixing ratio of the polymer and the photosensitizer in the photoresist composition of the present invention is not particularly limited, but is usually 1 to 100 parts by weight of the photosensitizer, preferably 5 to 50 parts by weight per 100 parts by weight of the polymer. You.

The photoresist composition of the present invention is preferably used in the form of a solution in which a copolymer having a repeating unit represented by the general formula (1) and a photosensitive agent are dissolved in a suitable solvent.

Examples of such solvents include ethers such as dioxane, diethoxyethane, diethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetone, methyl ethyl ketone, methyl Ketones such as isobutyl ketone, cyclopentanone and cyclohexanone; esters such as ethyl acetate, butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate and dimethyl oxalate; Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone And the like, lactones such as γ-butyrolactone, sulfoxides such as dimethyl sulfoxide, and the like. These solvents may be used alone or in combination of two or more.

The photoresist composition according to the present invention may optionally contain known additives, such as surfactants, dyes, stabilizers, and sensitizers, which are commonly used in photoresists.

 Next, the present invention will be described in more detail with reference to specific examples.

Synthesis Example 1 (Synthesis of Copolymer 1) In a nitrogen atmosphere, maleic anhydride-styrene copolymer 10.0 g (maleic anhydride unit 0.05 mol) in 30 ml of dehydrated DMF
SMA-1000, manufactured by ARCO Chemical Co.), and a solution of 10.18 g of β-aminoethylphenol suspended in 30 ml of dehydrated DMF is gradually added to the solution. 80 ° C
After heating and stirring for 9 hours, 15 ml of dehydrated toluene is added. The mixture is heated to reflux at 140 ° C. for 9 hours while removing water due to the dehydration reaction.

Thereafter, the reaction mixture was cooled and poured into 500 ml of diethyl ether to precipitate a polymer. The obtained polymer was dissolved in tetrahydrofuran and poured into diethyl ether to precipitate the polymer. After performing this operation twice, the obtained crystals were dried to obtain a copolymer 1. FIG. 1 shows an infrared absorption spectrum of the copolymer 1.

Synthesis Example 2 (Synthesis of Copolymer 2) In a nitrogen atmosphere, maleic anhydride-styrene copolymer (maleic anhydride unit 0.05 mol, SMA-100
0) 10 g was dissolved, and a solution in which 3.39 g (0.025 mol) of β-β-aminoethylphenol was suspended in 30 ml of dehydrated DMF was gradually added. After heating and stirring this solution at 80 ° C. for 9 hours, 5.10 g (0.049 mol) of γ-aminobutyric acid was added,
The mixture was further heated and stirred at 80 ° C. for 9 hours. After adding 15 ml of dehydrated toluene, a dehydration reaction and purification were performed in the same manner as in Synthesis Example 1 to obtain a copolymer 2. FIG. 2 shows the infrared absorption spectrum of the obtained copolymer 2.

Synthesis Example 3 (Synthesis of Copolymer 3) Copolymer 3 was obtained in exactly the same manner as in Synthesis Example 2 except that 5.5 g (0.074 mol) of n-butanol was used instead of γ-aminobutyric acid in Synthesis Example 2 above. FIG. 3 shows an infrared absorption spectrum of the copolymer 3.

Synthesis Example 4 (Synthesis of Copolymer 4) Copolymer 4 was obtained in exactly the same manner as in Synthesis Example 3 except that 9.0 g (0.074 mol) of phenethyl alcohol was used instead of n-butanol in Synthesis Example 3. FIG. 4 shows an infrared absorption spectrum of the copolymer 4.

Example 1 A copolymer was prepared by dissolving the copolymer synthesized in the above synthesis example and the photosensitive agent shown in Table 1 in 83 parts by weight of methyl cellosolve acetate shown in Table 1 by weight. These photoresist compositions were applied on a quartz plate with a spinner and dried at 85 ° C. for 30 minutes to form films. This film was exposed with a low-pressure mercury lamp (UL2-1BQ manufactured by Ushio Inc.) to
The transmittance per μm before and after exposure at m was measured. These films were etched under the following conditions, and the amount of film reduction was measured. The results are shown in Table 1.

From these results, it can be seen that the photoresist composition according to this example has a better transmittance before and after exposure than OFPR-800 which is a conventional positive resist for g-line.

Further, the dry etching resistance is equivalent to that of the conventional g-line resist.

Dry etching conditions according to this example Gas: SiCl ₄ , BCl ₃ , Cl ₂ , SF ₆ , O ₂ Pressure: 6.0 Pa Power: 650 W Etching time: 6 minutes Example 2 The photoresist composition of this example was applied on a silicon wafer and prebaked at 85 ° C. for 30 minutes. The film thickness is 1 μm
It was applied so that This photoresist film is mainly 254n
Exposure was performed using a low-pressure mercury lamp (UL2-1BQ manufactured by Ushio Inc.) that emits light of m, and developed with an aqueous solution of tetramethylammonium hydroxide having the concentration shown in the table.

The residual film for each exposure time was measured to create a characteristic curve. From this characteristic curve, the γ value of the photoresist of the present embodiment,
The sensitivity (Eth) and the amount of film reduction were determined and are shown in Table 2. As a reference example, a commercially available g-line photoresist was also measured.

This table shows that the photoresist composition of the present invention has a higher γ value, that is, a higher contrast than a commercially available g-line positive resist.

Example 3 Photoresist composition No. 1 was applied on a silicon wafer and dried at 85 ° C. for 30 minutes to provide a photosensitive film having a thickness of 1.0 μm. 6 with KrF excimer laser stepper with numerical aperture 0.37
After pattern exposure by irradiating with 00mj light, development with a 0.22 ON tetramethylammonium hydroxide aqueous solution resulted in clear resolution of a 0.35 μm line and space pattern.

<Effects of the Invention> As specifically described above in connection with the examples, the photoresist composition for far ultraviolet light according to the present invention has a far ultraviolet region,
In particular, since the transmittance of KrF excimer laser light at 248 nm is high, a resist pattern with high resolution can be obtained by using the photoresist composition of the present invention. In addition, the photoresist composition of the present invention has the same drum etching resistance as a conventional g-line photoresist despite having high transmittance to far ultraviolet light. Therefore, the present invention is particularly suitably used for manufacturing an ultra-high integration semiconductor device.

[Brief description of the drawings]

FIGS. 1, 2, 3 and 4 show synthesis examples 1 and 2, respectively.
4 is an infrared absorption spectrum of the copolymer obtained in 2, 3, and 4.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeshi Kotani 236 Nakai, Tatsuno-cho, Tatsuno-shi, Hyogo Nagase Electronics Chemical Co., Ltd.Hyogo Plant (72) Inventor Mitsuhiko Sano 236 Nakai, Tatsuno-cho, Tatsuno-shi, Hyogo (56) References JP-A-61-162039 (JP, A) JP-A-63-298340 (JP, A) JP-A-62-229140 (JP, A) JP-A-62-169155 (JP) JP, A) JP-A-62-255934 (JP, A) JP-A-2-32350 (JP, A)

Claims (1)

(57) [Claims] 1. A photoresist composition for far ultraviolet light comprising a copolymer having a repeating unit represented by the following general formula and a photosensitizer, which is used for far ultraviolet light exposure of 313 nm or less. In the formula, R ₁ represents hydrogen or a methyl group, R ₂ represents an alkyl group, an aralkyl group, R ₃ represents a hydrogen, an alkyl group, an alkenyl group, an aralkyl group, or an aryl group, and m represents an integer of 1 to 6. , N ₁ , n ₂ , n ₃ , n ₄ and n ₅ represent mol% of each repeating unit and are in the following ranges, respectively. n ₁ = 25 to 80, n
_{2 = 10~70, n 3 = 0~40} , n 4 = 0~40, n 5 = 0~10.