JP2848611B2 - Photoresist composition and pattern forming method - Google Patents

Description

The present invention relates to a novel photoresist composition and a method for forming a pattern using the same, and more specifically, to 313 nm.
It is suitable when the following deep ultraviolet light, particularly light using a KrF excimer laser 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. The resolution R of the resist in the reduction projection exposure method is represented by Rayleigh's equation R = kλ / NA. As a method for improving the resolution, the numerical aperture of the lens represented by NA is increased. There are three methods of shortening the wavelength of (λ) and reducing k determined by the resist process. 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. But stepper high
NA conversion is the depth of focus (DOF) expressed by the following formula, 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) is being developed.

By the way, a photoresist made of alkali-soluble novolak resin and naphthoquinonediazidesulfonic acid ester is used for a conventional stepper using g-line (436 nm) and i-line (365 nm) as light sources. These photoresists have the property of being transparent when exposed to g-line and i-line, so that a high-resolution pattern can be obtained. Therefore, these photoresists are also used in a recently developed excimer laser stepper device as described above.

<Problems to be Solved by the Invention> However, the photoresist comprising the alkali-soluble novolak resin and the naphthoquinonediazidesulfonic acid ester described above has an excessively high absorptivity for far ultraviolet rays having a wavelength of 313 nm or less. There is a problem that light does not reach and gives an overcut profile. Furthermore, these photoresists have a problem that, when exposed to far ultraviolet light, the photodegradation products of the photosensitizer absorb the exposure light, so that the transmittance is not improved.

A diazomeldrum acid derivative has been reported as a photosensitizer that solves these problems (IEEE Trans. Electron).
Devices, ED-28, 1300, 1981 ). However, these photosensitive agents become transparent upon exposure, but have a drawback that they sublime during prebaking of the resist. In addition, diazopiperidinedione derivatives (Proc. Of SPIE V) are used as photosensitizers for deep ultraviolet light.
ol. 771, 2, 1987 ), 2-diazo-cyclohexane-1,3-
Dione derivatives (JP-A-61-240237) or α-
Phosphoryl-substituted diazole carbonyl compounds (JP-A-61-1986)
Photoresists using such materials have been reported, but all have the disadvantage that the difference in transmittance at 248 nm between before and after exposure is small.

The present invention overcomes the above-mentioned problems, is alkali-developable, has a large difference in transmittance between before and after exposure to far ultraviolet light, particularly KrF excimer laser light, and can obtain a high-contrast pattern. The purpose of the present invention is to provide a photoresist composition having excellent characteristics and a method for forming a pattern using the same.

<Means for Solving the Problems> The present inventors have conducted intensive studies to develop a photoresist composition and a pattern forming method having the above-mentioned excellent characteristics. As a result, a photoresist comprising a photosensitive agent and an alkali-soluble resin was obtained. In the composition, the above object can be achieved by using a specific azide compound as the photosensitive agent, and exposing the photosensitive film of the photoresist composition to far ultraviolet light having a wavelength of 313 nm or less and developing with an alkali developer. Was found.

The photoresist composition according to the present invention based on this finding has the following general formula (1) Where, R ₁ and R ₂ represent an alkyl group, an alkenyl group, an aryl group or an aralkyl group; R ₃ and R ₄ represent an alkyl group, an aryl group, an aralkyl group, an alkoxyl group or an aryloxyl group; When X represents NH, And X represents O or NH.

Novolak resin, poly (hydroxystyrene) and general formula (2) And an alkali-soluble resin selected from a copolymer having a repeating unit having a structure represented by the following formula:

Further, a pattern forming method using such a photoresist composition is represented by the general formula (1) Where, R ₁ and R ₂ represent an alkyl group, an alkenyl group, an aryl group or an aralkyl group; R ₃ and R ₄ represent an alkyl group, an aryl group, an aralkyl group, an alkoxyl group or an aryloxyl group; When X represents NH, And X represents O or NH.

Novolak resin, poly (hydroxystyrene) and general formula (2) However, in the formula, R ₅ represents hydrogen, an alkyl group or an aryl group, R ₆ and R ₇ represent hydrogen, OH, COOH, SO ₃ H or OCOR ₉ (R ₉ is an alkyl group); Represents an integer of 6.

A photosensitive film comprising an alkali-soluble resin selected from a copolymer having a repeating unit having a structure represented by
It is characterized in that exposure is carried out using far-sighted light having a wavelength of 313 nm or less and development is carried out with an alkali developing solution.

 Hereinafter, the present invention will be described in detail.

As the photosensitizer of the photoresist composition of the present invention, a compound represented by the above general formula (1) is used. When the substituents in the general formula (1) are more specifically exemplified, R ₁ ,
R ₂ is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclohexyl group; a substituted or unsubstituted aryl group such as a phenyl group, a tolyl group or a naphthyl group; Alkenyl groups such as a group, allyl group, propenyl group and butenyl group, and R ₃ and R ₄ are methyl group, ethyl group,
Alkyl groups such as butyl group and cyclohexyl group; alkoxyl groups such as methoxyl group, ethoxyl group and butoxyl group; substituted or unsubstituted aryl groups such as phenyl group, tolyl group and naphthyl group, and aryloxyl groups such as phenoxyl group. be able to.

The compound represented by the general formula (1) is described in Chem. Ber. 102 , 2216
(1969) and Chem. Ber. 103 , 1477 (1970).

The photosensitive agent represented by the general formula (1) is a diazopiperidinedione derivative disclosed in the aforementioned patent or literature,
Compared with a 2-diazo-cyclohexane-1,3-dione derivative or an α-phosphoryl-substituted diazocarbonyl compound, the ratio of absorbance before and after exposure at 248 nm, which is the wavelength of far ultraviolet light, particularly KrF excimer laser light. ₀ /
ε _非常 is very large. Therefore, when using a photoresist containing these photosensitizers and exposing using KrF excimer laser light, the exposure makes the resist layer transparent, the light reaches the bottom of the resist film, and the resist pattern with a good profile Is obtained.

Examples of the alkali-soluble resin in the resist composition of the present invention include a novolak resin, poly (hydroxystyrene), and an alkali-soluble copolymer having an imide structure. As the novolak resin, for example, phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,5-xylenol, 3,4-xylenol, 3,5-xylenol, α-naphthol or β
-Phenols such as naphthol and formaldehyde,
Examples include condensates with aldehydes such as acetaldehyde and benzaldehyde. Examples of the poly (hydroxystyrene) include poly (o-hydroxystyrene), poly (m-hydroxystyrene), poly (p-hydroxystyrene), poly (α-methyl-o-hydroxystyrene), and poly (α-methyl). -M-hydroxystyrene), poly (α-methyl-m-hydroxystyrene)
Or a partially acetylated or silylated product thereof. The alkali-soluble copolymer having an imide structure is a copolymer having a repeating unit having a structure represented by the following general formula (2).

In the formula, R ₅ represents hydrogen, an alkyl group or an aryl group, R ₆ and R ₇ represent hydrogen, OH, COOH, SO ₃ H or OCOR ₉ (R ₉ is an alkyl group); Represents an integer.

These base polymers can be produced by known methods described in JP-A-61-162039, JP-A-62-151408, JP-A-62-151409 and the like.

The photoresist composition of the present invention is preferably used in the form of a solution obtained by dissolving the photosensitive agent represented by the general formula (1) and the alkali-soluble resin in a suitable solvent. Examples of such solvents are dioxane, diethoxyethane,
Ethers such as diethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and ethyl acetate , Butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, esters such as dimethyl oxalate, N, N-dimethylformamide,
Examples thereof include amides such as N, N-dimethylacetamide, pyrrolidones such as N-methylpyrrolidone, lactones such as γ-butyrolactone, and sulfoxides such as dimethylsulfoxide. These solvents may be used alone or in combination of two or more.

Although there is no particular limitation on the mixing ratio of the photosensitive agent and the alkali-soluble resin in the photoresist composition of the present invention, usually, per 100 parts by weight of the alkali-soluble resin,
The photosensitive component is blended in an amount of 1 to 100 parts by weight, preferably 5 to 50 parts by weight.

The photoresist composition of the present invention may contain, if necessary, additional components used in ordinary photoresists, such as surfactants, dyes, stabilizers, and sensitizers.

After the photoresist composition of the present invention is applied on a substrate to form a film, it is effective to use in a method of forming a pattern using far ultraviolet light, particularly 248 nm light oscillated by a KrF excimer laser. .

Next, an example of the pattern forming method of the present invention will be described. First,
A solution obtained by dissolving the photoresist composition of the present invention in a solvent is applied on a substrate such as a semiconductor wafer by a spinner, for example, and dried to form a photosensitive film. The drying conditions at this time are determined in consideration of the thermal stability of the used photosensitive agent, the boiling point of the solvent, and the like. The thickness of the photosensitive film to be formed is not particularly limited.
When the thickness is larger than μm, the image becomes defocused in the reduction projection exposure apparatus. Therefore, the thickness is usually preferably 50 to 5 μm, more preferably 1000 to 3 μm.

In the method of the present invention, after the above-mentioned photosensitive film is formed, pattern exposure is performed by irradiating far ultraviolet light having a wavelength of 313 nm or less, particularly preferably KrF excimer laser light, through a predetermined pattern. Thereafter, the desired fine pattern is developed by developing the resist layer with an alkaline developer such as an aqueous solution of an inorganic alkali such as sodium hydroxide or potassium hydroxide, or an aqueous solution of an organic alkali such as tetramethylammonium hydroxide or choline. Obtainable.

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

Synthesis example (diphenylphosphinyldiethylcarbamoyldiazomethane) N, N-diethylacetamide 2 refluxed in a nitrogen atmosphere
15.0 g of ethyldiphenylphosphine oxide in 4.3 g
Was added dropwise over about 1 hour. After the dropwise addition, the mixture was further refluxed for 30 minutes.
After cooling, n-hexane was added to the reaction mixture to precipitate crystals. The precipitated crystals were filtered and dried to obtain diphenylphosphinyldiethylcarbamoylmethane. 15.82 g of the obtained diphenylphosphinyldiethylcarbamoylmethane and potassium t-butoxide were dissolved in 125 ml of a 4: 1 mixed solvent of benzene and tetrahydrofuran,
The mixture was heated under reflux in a nitrogen atmosphere for 10 minutes. This mixture is brought to 0 ° C
Cooled to p-toluenesulfonyl azide 9.86
g was dissolved in 125 ml of benzene. 1 at the same temperature
After further stirring at room temperature for 15 hours, 150 ml of water was added. After extraction with benzene, the benzene layer was washed with an alkali. When benzene was distilled off and concentrated, crystals precipitated. The precipitated crystals were filtered and further recrystallized from isopropyl ether to obtain the following diphenylphosphyldiethylcarbamoyldiazomethane (photosensitive agent 1).

Similarly, the following photosensitive agents 2 and 3 were produced.

Examples 1 and 2 and Reference Examples 1 to 3 1 part by weight of each of the photosensitizers 1 to 3 described above and 10 parts by weight of the alkali-soluble resin shown in Table 1 were dissolved in methyl cellosolve acetate to prepare a photoresist composition. These photoresist compositions are applied on a quartz plate with a spinner and heated at 85 ° C.
After drying for 30 minutes, a film was formed. The film was exposed with a low-pressure mercury lamp, and the transmittance at 248 nm before and after exposure was measured. The results are also shown in Table 1.

For comparison, 2,3,4-trihydroxybenzophenone, which is a currently used photoresist photosensitizer, and 1,2-
A photosensitive film using an ester with naphthoquinonediazide-5-sulfonic acid is referred to as Reference Example 2, and a photosensitive film is referred to as Reference Example 3 using diphenylphosphinylbenzoyldiazomethane as a photosensitive agent disclosed in JP-A-61-223837. Similarly 24
The transmittance before and after exposure at 8 nm was measured. Table 1 also shows these results.

From the results shown in Table 1, the difference in transmittance between the photoresist composition of Example 1 before and after exposure compared to Reference Examples 2 and 3 (T
∞−T ₀ ) is large.

Further, it can be seen that Example 2 has a larger difference (T∞−T ₀ ) in transmittance before and after exposure than in Reference Example 1.

Example 3 The photoresist of Example 1 was applied on a silicon wafer and dried at 85 ° C. for 30 minutes to form a photosensitive film having a thickness of 1.0 μm. 1 with KrF excimer laser stepper with numerical aperture 0.37
After pattern exposure by irradiating 60mj light, developed with 0.180N tetramethylammonium aqueous solution, 0.3
The line and space pattern of μ could be clearly resolved.

<Effects of the Invention> The photoresist composition of the present invention has a deep ultraviolet region, particularly KrF.
Since the difference between the transmittance of the excimer laser light before and after exposure at 248 nm is large, it is possible to form a photosensitive film using such a photoresist composition and obtain a high-resolution resist pattern by exposing with a deep ultraviolet light. it can.
Therefore, the present invention is particularly suitably used for manufacturing a highly integrated semiconductor device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03F ^7/ 00-7/18

Claims (2)

(57) [Claims] 1. The general formula (1) Where, R ₁ and R ₂ represent an alkyl group, an alkenyl group, an aryl group or an aralkyl group; R ₃ and R ₄ represent an alkyl group, an aryl group, an aralkyl group, an alkoxyl group or an aryloxyl group; When X represents NH, And X represents O or NH. Novolak resin, poly (hydroxystyrene) and general formula (2) (Where R ₅ represents hydrogen, an alkyl group or an aryl group, R ₆ and R ₇ represent hydrogen, OH, COOH, SO ₃ H or OCOR ₉ (R ₉ is an alkyl group), and n is 0 A photoresist composition comprising an alkali-soluble resin selected from a copolymer having a repeating unit having a structure represented by the following formula: 2. The general formula (1) Where, R ₁ and R ₂ represent an alkyl group, an alkenyl group, an aryl group or an aralkyl group; R ₃ and R ₄ represent an alkyl group, an aryl group, an aralkyl group, an alkoxyl group or an aryloxyl group; When X represents NH, And X represents O or NH. Novolak resin, poly (hydroxystyrene) and general formula (2) (Where R ₅ represents hydrogen, an alkyl group or an aryl group, R ₆ and R ₇ represent hydrogen, OH, COOH, SO ₃ H or OCOR ₉ (R ₉ is an alkyl group), and n is 0 A photosensitive film comprising an alkali-soluble resin selected from a copolymer having a repeating unit having a structure represented by the following formula:
A pattern forming method, comprising exposing to light using far-sighted light of 313 nm or less and developing with an alkali developing solution.