JP3060712B2 - Positive photoresist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a positive photoresist composition. More specifically, the present invention relates to a positive photoresist composition which contains an alkali-soluble resin, a quinonediazide-based photosensitive compound and a solvent as main components and is sensitive to radiation such as ultraviolet rays, far ultraviolet rays, electron beams, and X-rays.

[0002]

2. Description of the Related Art A positive photoresist composition is usually mainly composed of an alkali-soluble resin, a photosensitive compound and a solvent. At present, as a positive photoresist composition for semiconductors generally used, a novolak resin is used as an alkali-soluble resin, and a condensate (esterified product) of naphthoquinonediazidosulfonic acid chloride and hydroxybenzophenone is used as a photosensitive agent. These are dissolved in a solvent such as ethyl cellosolve acetate (see, for example, JP-A-58-17112 and JP-A-62-136637).

Various processes for forming a pattern of such a positive type photoresist are known, and the general principle thereof is as follows. That is, in the radiation-irradiated portion, the quinonediazide-based photosensitive compound (hereinafter, referred to as "photosensitizer") is decomposed to generate indenecarboxylic acid, which is easily dissolved in an aqueous alkaline solution. On the other hand, in the unirradiated portion, the photosensitizer inhibits the solubility of the alkali-soluble novolak resin in the alkali developer (hereinafter, this inhibitory effect is referred to as a “masking effect”). Hold the rate. As a result, a high-resolution resist pattern can be obtained.

[0004]

In recent years, integrated circuits have been miniaturized in accordance with high integration, and sub-micron pattern formation has been demanded, and high resolution and high sensitivity are required. There is a need for a positive photoresist. Also, with miniaturization, dry etching has become mainstream instead of conventional wet etching. Due to this dry etching, the heat resistance of the resist has been required more than before. Generally, improvement in heat resistance is achieved by increasing the molecular weight of the alkali-soluble novolak resin used in positive photoresists. This causes a very serious inconvenience that the performance of the device becomes worse. An object of the present invention is to provide a positive photoresist composition having excellent heat resistance without deteriorating sensitivity and resolution as compared with conventional products in view of the above background.

[0005]

Means for Solving the Problems In order to solve such problems, the present inventors have made intensive studies and as a result, as a photosensitive compound, a naphthoquinonediazide compound as a photosensitive component was converted to an alkali as a binder resin. By selecting a compound that is combined with another low-molecular-weight novolak resin, which is a soluble resin, and that the novolak resin is a polycondensate of a specific phenolic compound and a hydroxyaromatic aldehyde, It has been found that a photoresist containing this photosensitive compound has high heat resistance without deteriorating sensitivity and resolution as compared with conventional products, and has reached the present invention.

That is, the gist of the present invention is to provide a positive photoresist composition comprising an alkali-soluble resin, a quinonediazide-based photosensitive compound, and a solvent, wherein the alkali-soluble resin is at least one kind represented by the following general formula [A]: A polycondensate [C-1] of a phenolic compound and at least one ketone or aldehyde represented by the following general formula [B-1], and gel permeation chromatography of the polycondensate [C-1] The weight average molecular weight in terms of polystyrene is 2,500 to 30,000, and the quinonediazide-based photosensitive compound is at least one phenolic compound represented by the following general formula [A] and at least one represented by the following general formula [B-2] Polycondensate with a kind of hydroxy aromatic aldehyde [C-2]
Wherein the polycondensate [C-2] has a polystyrene-equivalent weight average molecular weight of 600 to 2,000.

[0007]

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[0008]

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[0009]

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Wherein R ¹ represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a hydroxyl group, and R ² and R ³ represent a hydrogen atom and an alkyl group having 1 to 4 carbon atoms, respectively. group, an aryl group or an aralkyl group, R ⁴
Is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or 1 to
4 represents an alkoxy group, 1 represents an integer of 0 to 3, m and n each represent an integer of 1 to 5, and the total of m and n is 5. However, when l or m is an integer of 2 or more, a plurality of R
¹ or R ⁴ may be the same or different. )

Hereinafter, the present invention will be described in detail. In the positive photoresist composition of the present invention, the alkali-soluble resin as a binder resin includes at least one phenolic compound represented by the general formula [A] and at least one phenolic compound represented by the general formula [B-1]. It is a polycondensate with a ketone or aldehyde (hereinafter sometimes referred to as a novolak resin). Carbon number 1 in the general formula [A]
Examples of the alkyl groups (1) to (4) include a methyl group, an ethyl group, and an n-
Examples of the alkoxy group having 1 to 4 carbon atoms such as a propyl group include a methoxy group, an ethoxy group, and an n-propoxy group.

Specific examples of the phenolic compound represented by the general formula [A] include phenol; o-cresol, m-cresol, p-cresol, 3,5-
Dimethylphenol, 2,5-dimethylphenol,
2,3-dimethylphenol, 3,4-dimethylphenol, 2,3,5-trimethylphenol, 3,4,5
-Trimethylphenol, 2-t-butylphenol,
3-t-butylphenol, 4-t-butylphenol, resorcinol, 2-methylresorcinol, 4-
Methylresorcinol, 5-methylresorcinol, catechol, 4-t-butylcatechol, pyrogallol,
2-methoxyphenol, 3-methoxyphenol, 4
-Methoxyphenol, 2-methoxyresorcinol,
2,3-dimethoxyphenol, 2,5-dimethoxyphenol, 3,5 dimethoxyphenol, 2-ethylphenol, 3-ethylphenol, 4-ethylphenol, 2,3,5-triethylphenol, 3,4,5-
Triethylphenol, 2,3-diethylphenol,
3,5-diethylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol, 2-propylphenol, 3-propylphenol, 4-propylphenol, 2-methoxy-5
Monohydric or polyhydric phenol which may be substituted with an alkyl group such as -methylphenol and 2-t-butyl-5-methylphenol, and an alkoxy group.

In the general formula [A], R ¹ is preferably a methyl group or a hydroxyl group. In particular,
o-cresol, m-cresol, p-cresol,
3,5-dimethylphenol, 2,5-dimethylphenol, 2,3-dimethylphenol, 3,4-dimethylphenol, 2,3,5-trimethylphenol, 3,
4,5-trimethylphenol, resorcinol, 2-
Methylresorcinol and pyrogallol are preferred. These compounds are used alone or in combination of two or more.

In the general formula [B-1], examples of the alkyl group represented by R ² and R ³ include the same as those of R ^1, and examples of the aryl group include a phenyl group, a naphthyl group and the like. Examples include a benzyl group. Examples of the ketone or aldehyde represented by the general formula [B-1] include aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde, acetone, methyl ethyl ketone, acetophenone,
And ketones such as benzophenone. Of these, formaldehyde, alkyl aldehydes having 2 to 4 carbon atoms, benzaldehyde, and acetone are preferred. More preferred are formaldehyde, acetaldehyde and acetone. These compounds are used alone or in combination of two or more.

As a method for producing the above alkali-soluble resin, a conventional method is used, for example, in the presence of an acid catalyst.
A method of mixing and heating to perform polycondensation is exemplified. As the acid catalyst, for example, an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid or the like, or an organic acid such as formic acid, oxalic acid or acetic acid is used, and these may be used alone or in combination. In the polycondensation reaction of the present invention, a reaction solvent is not usually used, but a solvent can be used. These solvents include, for example, methanol,
Examples include alcohols such as ethanol and propanol, and ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether. The reaction temperature varies depending on the phenolic compound represented by the general formula [A], but is usually about 10 to 200 ° C, preferably about 20 to 150 ° C. After completion of the reaction, the internal temperature is generally raised to about 150 ° C. to 250 ° C., the unreacted raw materials, the acid catalyst and water are distilled off under reduced pressure, and then the molten alkali-soluble resin is taken out. In the case of using a reaction solvent, the reaction mixture can be added to a solvent such as water after the completion of the reaction to precipitate the alkali-soluble resin, and the precipitate can be obtained by filtering and drying. These alkali-soluble resins may be used alone or in combination of two or more. The alkali-soluble resin of the present invention has a weight average molecular weight in terms of polystyrene (hereinafter referred to as “MW”) determined by gel permeation chromatography of 2500 to 3000.
0. When the MW is less than 2500, the heat resistance of the positive type photo rest deteriorates, and when it exceeds 30,000, the sensitivity deteriorates remarkably and it is difficult to obtain a good alkali-soluble resin.

On the other hand, as the quinonediazide-based photosensitive compound used in the present invention, at least one phenolic compound represented by the above-mentioned general formula [A] and the above-mentioned general formula [B-
It is an essential requirement to use a quinonediazidesulfonic acid ester of the polycondensate [C-2] with at least one hydroxy aromatic aldehyde represented by 2).
Examples of the phenolic compound represented by the general formula [A] as a raw material of the quinonediazide-based photosensitive compound include the same compounds as those exemplified as the phenolic compound as a raw material of the alkali-soluble resin as the binder resin. Can be done. These compounds may be used alone or in combination of two or more.

On the other hand, as the alkyl group and the alkoxy group in the general formula [B-2], those similar to R ¹ can be mentioned. Examples of the hydroxy aromatic aldehyde represented by the general formula [B-2] include o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, vanillin, orthovanillin, 4-hydroxy-3-methylbenzaldehyde, 6-dimethyl-4-hydroxybenzaldehyde, 3,6-dimethyl-4-hydroxybenzaldehyde, 3,5-dimethyl-4-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 2,5-dihydroxy Benzaldehyde, 3,4-dihydroxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 3-hydroxy-
4-methoxybenzaldehyde and the like can be mentioned. These compounds are used alone or in combination of two or more.

As a method for producing a polycondensate [C-2] from the phenolic compound represented by the general formula [A] and the hydroxyaromatic aldehyde represented by the general formula [B-2], The same method as for the soluble resin [C-1] is adopted. However, the weight average molecular weight in terms of polyethylene of the polycondensate [C-2] is 600 to 200.
0, preferably 700-1800. When the molecular weight of the polycondensate [C-2] is too small, a satisfactory masking effect cannot be obtained, and a good pattern profile cannot be obtained. Conversely, if the molecular weight is too large,
The sensitivity is significantly deteriorated.

The quinonediazidosulfonyl group for esterifying the hydroxyl group of the above polycondensate [C-2] includes 1,2
-Benzoquinonediazide-4-sulfonyl group, 1,2-
Examples include a naphthoquinonediazide-4-sulfonyl group and a 1,2-naphthoquinonediazide-5-sulfonyl group. Esterification rate of quinonediazide sulfonic acid ester of polycondensate [C-2], that is, polycondensate [C-2]
Of the quinonediazidosulfonyl group with respect to hydrogen of the hydroxyl group of [(quinonediazidosulfonyl group per molecule of quinonediazidesulfonic acid esterified product of polycondensate [C-2]) / (hydroxyl group per molecule of polycondensate [C-2]) Number). ] Is about 30 to 100%, preferably about 35 to 80%.

The esterification reaction of the polycondensate [C-2] is usually carried out by reacting the polycondensate [C-2] with a predetermined amount of quinonediazidesulfonic acid chloride in an organic solvent at room temperature. can do. In the present invention, the polycondensate [C-2] synthesized from the specific raw materials described above.
A quinonediazide-based photosensitive component is used as the photosensitive compound. At this time, two or more of the above photosensitive compounds may be used in combination. Furthermore, as long as the effect of the photosensitive compound is not significantly impaired, 1,2-naphthoquinonediamide-5-polyhydroxybenzophenone can be used.
Some other known photosensitive compounds such as sulfonic acid esters may be used in combination.

The solvent used in the present invention may be any solvent that can dissolve the quinonediazide-based photosensitive compound and the alkali-soluble resin.
From the viewpoint of operability during use, those having a boiling point of 100 to 180 ° C are preferred. Examples of these solvents include ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, and propylene glycol monomethyl ether acetate; ether alcohols such as ethyl cellosolve, methyl cellosolve and propylene glycol monomethyl ether; and carboxylic acids such as ethyl acetate and butyl acetate. Acid esters, kents such as γ-butyrolactone, cyclic ketones such as cyclohexanone, carboxylic acid esters of dibasic acids such as oxalate diel, dityl malonate, and glycols such as ethylene glycol diacetate and propylene glycol diacetate. Oxycarboxylates such as dicarboxylates, ethyl 2-oxypropionate, methyl 3-methoxypropionate, and ethyl 3-ethoxypropionate; . These solvents can be used alone or in combination of two or more.

The concentration of the alkali-soluble resin in the photoresist composition of the present invention is usually 1 to 30% by weight. The concentration of the quinonediazide-based photosensitive compound is
0.1 to 15% by weight. Further, the ratio of the quinonediazide type photosensitive compound to the alkali-soluble resin is usually 0.1 to 0.5 times by weight. In addition, a surfactant such as polyoxyethylene ethers or fluorine-based alkyl esters can be added to the photoresist composition of the present invention, if necessary, in order to improve poor coating properties such as striation. The amount of these additives is usually 2% by weight or less, preferably 1% by weight or less. Further, a dye or the like can be added to reduce the influence of irregularly reflected light from the substrate during image transfer, and a sensitizer or the like can be added to improve sensitivity.

The photoresist composition of the present invention is used through various steps such as application to a substrate, exposure and development according to a known method. The substrate on which the photoresist composition is applied is a semiconductor substrate such as a silicon wafer. The application of the photoresist composition to such a substrate is usually performed using a spin coater, and the thickness of the photoresist composition is usually about 0.3 to 5 μm. Usually, after applying the photoresist composition, the substrate is heated on a hot plate or the like, the solvent is removed, and then the film is exposed through a mask to bake a desired pattern on the substrate. For exposure, g-line (436 nm), i
Light having a wavelength of 330 to 450 nm, such as a line (365 nm), is preferably used. After exposure, the substrate may be 90-
After heating at about 120 ° C. for about 60 to 120 seconds, development is performed with an alkaline aqueous solution. Examples of the aqueous alkali solution include inorganic alkalis such as potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia, primary amines such as ethylamine and n-propylamine, diethylamine, and di-n-propylamine. Alkaline aqueous solutions comprising aqueous solutions of secondary amines such as tertiary amines such as triethylamine and trimethylamine, and quaternary ammonium bases such as tetramethylammonium hydroxide and trimethylhydroxyethylammonium hydroxide are preferably used. . Incidentally, an alcohol, a surfactant and the like may be added to the developer as needed.

[0024]

The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the invention. still,
In the following examples, the molecular weight indicates the weight average molecular weight in terms of polystyrene as a result of analysis by gel permeation chromatography, and the esterification ratio indicates the esterification ratio obtained from the charged molar ratio.

Novolak Resin Synthesis Example 1 m-cresol 237.9 in a 1 l separable flask
g, 190.3 g of p-cresol, 53.7 g of 2,5-xylenol, 15 g of oxalic acid, and 1 ml of 35% hydrochloric acid.
1 g is added dropwise. After that, the internal temperature was raised to 95 ° C and 37%
200.0 g of formalin aqueous solution was added dropwise, and the reaction was carried out for 5 hours while maintaining the temperature. Then the internal temperature is 180 ℃
Water was distilled out of the system while the temperature was raised over 1.5 hours. After the distillation, the internal temperature was further raised to 195 ° C., and the unreacted monomer was distilled off under reduced pressure of 20 torr. Resin (a) was obtained. The molecular weight of this resin was 4,500. Novolak Resin Synthesis Example 2 m-cresol 190.3 in a 1 l separable flask
g, 237.9 g of p-cresol, 53.7 g of 2,5-xylenol, and 15 g of oxalic acid.
The temperature was raised to 5 ° C., and 246.0 g of a 37% formalin aqueous solution was used.
The reaction was carried out for 5 hours while the temperature was maintained by dropping. Then, water was distilled out of the system while the internal temperature was raised to 180 ° C. over 1.5 hours, and after distilling off, the internal temperature was further raised to 195 ° C., and the unreacted monomer was reduced under reduced pressure of 20 torr. Was distilled off to obtain a novolak resin (b). The molecular weight of this resin is 6
500.

Novolak Resin Synthesis Example 3 A novolak resin (c) was obtained in the same manner as in the novolak resin synthesis example 2 except that 475.2 g of m-cresol, 15 g of oxalic acid and 196.4 g of a 37% aqueous solution of formalin were used.
The molecular weight of this resin was 986. Novolak Resin Synthesis Example 4 m-cresol 21.6 in a 200 ml four-necked flask
g, 2-hydroxybenzaldehyde 18.3 g, 35
0.5 ml of hydrochloric acid and 50 ml of ethanol were charged, the oil bath temperature was maintained at 100 ° C., and the mixture was heated under reflux for 7 hours to carry out a reaction. After completion of the reaction, the reaction solution was added dropwise to 1 liter of water with stirring to precipitate a crystal. The obtained crystals were collected by filtration, washed three times with 1 l of water, and dried to obtain a novolak resin (d). The molecular weight of this resin was 950.

Novolak Resin Synthesis Example 5 A novolak resin (e) was prepared in the same manner as in the novolak resin synthesis example 4 except that 18.3 g of 4-hydroxybenzaldehyde was used instead of 2-hydroxybenzaldehyde.
I got The molecular weight of this resin was 720. Photosensitizer Synthesis Example 1 18.92 g of novolak resin (d) and 24.12 g of 1,2-naphthoquinonediad-5-sulfonyl chloride
With 100 ml of acetone, 30 m of N-methylpyrrolidone
l of the mixed solvent, 9.85 g of triethylamine
Was added dropwise, and the mixture was reacted at room temperature for 2 hours. The reaction mixture was filtered to remove triethylamine hydrochloride. The filtrate was added to 1 liter of water with stirring, and the precipitated crystal was collected by filtration, washed with water and dried to obtain a photosensitive agent (P-1). The esterification ratio of the photosensitizer (P-1) is 50%.

Photosensitizer Synthesis Example 2 21.60 g of novolak resin (e) and 27.77 g of 1,2-naphthoquinonediad-5-sulfonyl chloride
With acetone 130 ml, N-methylpyrrolidone 36 m
of triethylamine 11.30
Photosensitive agent (P-2) was obtained in the same manner as in Photosensitive agent synthesis example 1 except that g was dropped. The esterification ratio of the photosensitizer (P-2) is 50%. Photosensitizer Synthesis Example 3 39.40 g of novolak resin (c) and 58.00 g of 1,2-naphthoquinonediad-5-sulfonyl chloride
With acetone 240 ml, N-methylpyrrolidone 65 m
of triethylamine 22.10
Photosensitive agent (P-3) was obtained in the same manner as in Photosensitive agent synthesis example 1 except that g was dropped. The esterification ratio of the photosensitizer (P-3) is 65%. Photosensitizer Synthesis Example 4 29.58 g of novolak resin (c) and 33.45 g of 1,2-naphthoquinonediad-5-sulfonyl chloride
With acetone 160 ml, N-methylpyrrolidone 43 m
of triethylamine 12.73
Photosensitive agent (P-4) was obtained in the same manner as in Photosensitive agent synthesis example 1 except that g was dropped. The esterification ratio of the photosensitizer (P-4) is 50%.

Preparation Example 1 of Photoresist Composition Novolak resin (a) as alkali-soluble resin
730 g and 2.030 g of the photosensitizer (P-1) were dissolved in 22.20 g of methyl 3-methoxypropionate.
The solution was filtered through a 2 μm membrane filter to obtain a photoresist composition (PR-1). Photoresist composition preparation examples 2 to 5 Photoresist composition in the same manner as photoresist composition preparation example 1 except that the alkali-soluble resin and photosensitive agent described in Table 1 below were combined in the ratios shown in Table 1. (PR
-2 to PR-5).

[0030]

[Table 1]

Examples 1-3 and Comparative Examples 1-2 Photoresist compositions (PR-1) to (PR-5) were
Patterning was performed by the following patterning method, and the sensitivity, critical resolution, and heat resistance were evaluated. The results are shown in Table 2.
In Table 2, the following symbols and terms have the following meanings, respectively.

[0032]

[Table 2] E ₀ : When the line & space pattern is 1: 1 on a 0.6 μm mask, the line width between the exposed and unexposed areas is reduced to 0.6 μm by developing with an alkali developer after exposure. There 1: display limit resolution of exposure honed in 1 exposure time: minimum resolvable line and space pattern heat resistance in the exposure amount E _0: when heated 5 minutes wafer on a hot plate, 5 [mu] m line-and Maximum temperature at which the space pattern is not deformed (at intervals of 5 ° C)

<Patterning Method> A photoresist composition is applied to a silicon wafer by a spin coater, and then heated on a hot plate at 80 ° C. for 90 seconds to remove the solvent and form a photoresist coating film having a thickness of 1.01 μm. did. This is a Nikon i-line stepper (NA =
After exposure at 0.5), the film was heated on a hot plate at 120 ° C. for 90 seconds, and then immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide at 23 ° C. for 60 seconds to develop.

[0034]

[Table 3]

[0035]

The photoresist composition of the present invention has good sensitivity and resolution and high heat resistance.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-279957 (JP, A) JP-A-3-228058 (JP, A) JP-A-2-10348 (JP, A) JP-A-2- 84414 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03F ^7/ 00-7/42

Claims (1)

(57) [Claims] 1. A positive photoresist composition comprising an alkali-soluble resin, a quinonediazide-based photosensitive compound and a solvent, wherein the alkali-soluble resin comprises at least one phenolic compound represented by the following general formula [A] and: It is a polycondensate [C-1] with at least one kind of ketone or aldehyde represented by [B-1], and the polycondensate [C-1] has a weight average molecular weight in terms of polystyrene by gel permeation chromatography. , 2,500 to 30,000, and a quinonediazide-based photosensitive compound comprising at least one phenolic compound represented by the following general formula [A] and the following general formula [B-
2] a polycondensate [C-2] with at least one hydroxy aromatic aldehyde represented by the formula [2] as a main component, and the above polycondensate [C-
2] is 600 to 2 in terms of polystyrene.
A positive photoresist composition having a molecular weight of 000. Embedded image Embedded image Embedded image (Wherein, R ¹ is an alkyl group having 1 to 4 carbon atoms,
R ² and R ³ each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
An aryl group or an aralkyl group, wherein R ⁴ is a hydrogen atom,
Represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, 1 represents an integer of 0 to 3, m and n each represent an integer of 1 to 5, and the total of m and n is 5 is there. However,
When l or m is an integer of 2 or more, a plurality of R ¹ or R ⁴ may be the same or different. )