JPH05142770A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To provide the positive type photoresist compsn. having excellent resolution, dry etching resistance and heat resistance. CONSTITUTION:The alkaline soluble novolak resin of the positive type photoresist compsn. contg. the alkaline soluble novolak resin and 1,2- naphthoquione diazide compd. is a novolak resin I obtd. by bringing phenols and formaldehyde into addition condensation reaction. The weight average mol.wt. in conversion of standard polystyrene obtd. by gel permeation chromatography ranges from 3000 to 15000 and the dispersion is <=2.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive photoresist composition containing a specific alkali-soluble novolac resin and a 1,2-naphthoquinonediazide compound, and is particularly sensitive to ultraviolet rays, far ultraviolet rays, X-rays, electron rays and the like. And a positive photoresist composition for producing an integrated circuit having a high degree of integration.

[0002]

2. Description of the Related Art As a photoresist for producing an integrated circuit, a negative photoresist in which a bisazide compound is mixed with a cyclized rubber, a positive photoresist in which an alkali-soluble resin and an alkali-insoluble 1,2-naphthoquinonediazide compound are used. It has been known. In the case of a negative photoresist, the cyclized rubber in the exposed area is three-dimensionally crosslinked and becomes insoluble in the developing solution, and the unexposed area is dissolved to form a resist pattern. At this time, there is a drawback that the resist pattern swells greatly in the developer and the resolution is poor. On the other hand, in the positive photoresist, the 1,2-naphthoquinonediazide compound in the exposed area is changed to indenecarboxylic acid, the effect of suppressing dissolution in the alkali-soluble resin is reduced, and the exposed area is dissolved to form a resist pattern.

At this time, the dimensional change of the unexposed portion forming the resist pattern is extremely smaller than that of the negative photoresist, so that a high-resolution resist pattern faithful to the mask pattern can be obtained. .. For this reason, positive-type photoresists have become the mainstream of high-resolution photoresists, and recently, 16M to 64MDR.
A resolution of 0.5 μm or less has been required for AM.

The high resolution of the resist pattern can be achieved by optimizing the composition and molecular weight of the resin used for the photoresist and increasing the oligomer content in the resin. However, on the other hand, if the oligomer content is increased, dry etching (13
There is a problem that the heat resistance at 0 to 150 ° C.) is insufficient and the resist pattern is thermally deformed. Therefore, a photoresist excellent in both resolution and heat resistance has been required.

[0005]

The present invention has been made in view of the above problems, and provides a high-resolution positive photoresist composition excellent in resolution, dry etching resistance, and heat resistance.

[0006]

The present invention relates to a positive photoresist composition containing an alkali-soluble novolac resin and a 1,2-naphthoquinonediazide compound, wherein the alkali-soluble novolac resin causes an addition condensation reaction of phenols and formaldehyde. A novolak resin produced by the method of having a polystyrene-equivalent weight average molecular weight of 3,000 to 15,000 as determined by gel permeation chromatography and a dispersity of 2.0.
The present invention relates to a positive photoresist composition characterized by the following.

The present invention will be described in more detail below. The alkali-soluble novolak resin used in the present invention is a polycondensation compound of phenols and formaldehyde, and the phenols used include phenol, m-cresol,
p-cresol, o-cresol, ethylphenol,
Butylphenol, 2,5-xylenol, 3,5-xylenol, 2,4-xylenol, 2,6-xylenol, 2,3,5-trimethylphenol, 2,3,6
-Trimethylphenol, resorcinol, catechol, hydroquinone, 1-naphthol, 2-naphthol, pyrogallol, 1,2,4-trihydroxybenzene and the like.

Of these, m-cresol and p-cresol are preferred from the viewpoint of resolution and heat resistance, and particularly preferred is a mixture of m-cresol in the range of 30 to 60% by weight and p-cresol in the range of 70 to 40% by weight. It is a novolac resin made from cresol and formaldehyde.

The weight average molecular weight of this novolak resin is 3
The dispersity (weight average molecular weight / number average molecular weight) is set to 2.0 or less. When the weight average molecular weight is less than 3,000, the heat resistance of the photoresist is remarkably inferior, while when it exceeds 15,000, the resolution of the photoresist is remarkably inferior. When the dispersity exceeds 2.0, the heat resistance of the photoresist decreases.

The molecular weight of the novolak resin is a value that can be calculated based on a calibration curve obtained by using standard polystyrene, and the gel permeation chromatography measurement is performed by using a gel pack GL-R42 manufactured by Hitachi Chemical Co., Ltd. as a column.
Each of 0, R430, and R440 is connected in series, and a detector is a differential refractometer and tetrahydrofuran is used as a solvent at a flow rate of 1.75 ml / min.

The alkali-soluble novolak resin is prepared by first synthesizing phenols and formaldehyde with a commonly used acid or an organic acid salt of a divalent metal as a catalyst, and then by using the obtained resin as a poor solvent for the resin. The degree of dispersion can be 2.0 or less by solvent extraction using a good solvent, fractionation by molecular weight by liquid chromatography, and the like.

The acid used as the catalyst may be either an inorganic acid or an organic acid, and hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, oxalic acid or the like is used. The organic acid salts of divalent metals include organic acid salts of magnesium, zinc, cobalt and the like.

The reaction can be carried out in a solvent or without a solvent, and may be carried out at 60 to 200 ° C. for 2 to 20 hours.

The poor solvent used for solvent extraction of the resin in the present invention includes chloroform, ethyl alcohol, 2-propyl alcohol, hexane, water, buffer solution, etc., and good solvents are tetrahydrofuran, methanol, dioxane, acetonitrile, acetone. , Pyridine, dimethyl sulfoxide, dimethyl acetamide, ethyl cellosolve acetate, methyl cellosolve acetate, butyl acetate, ethyl lactate, xylene and the like.

In order to remove the high molecular weight component, the resin is first dissolved in a good solvent, and the poor solvent is added thereto to precipitate the high molecular weight component.

To remove low molecular weight components, poor solvent is used for Soxhlet extraction and the like.

On the other hand, when fractionating by molecular weight by liquid chromatography, it is necessary to use the styrene resin type filler used for the measurement of the molecular weight as the column filler, and the silica type or acrylate resin type filler is used. As a result, the resin is modified during the fractionation or the resin is adsorbed on the filler, making it impossible to evaluate the photoresist characteristics.

Acetone is preferred as the solvent for fractionation, and tetrahydrofuran, which is usually used, is
Not preferred over polymerization.

The alkali-soluble novolac resin of the present invention is preferably used in an amount of 50 to 90 parts by weight, preferably 60 to 80 parts by weight, based on 100 parts by weight of the total amount of the novolac resin and the 1,2-naphthoquinonediazide compound. Is more preferable. If the amount is less than 50 parts by weight, the 1,2-naphthoquinonediazide compound is not completely decomposed by the short-time exposure that is usually performed, and it becomes difficult to form a resist pattern. On the other hand, if it exceeds 90 parts by weight, the effect of suppressing the dissolution by the photosensitizer becomes insufficient and the resist pattern is not formed.

On the other hand, the 1,2-naphthoquinonediazide compound of the present invention can be obtained by condensing 1,2-naphthoquinonediazide sulfonic acid chloride and a compound having a hydroxyl group in the presence of a weak alkali.

The compound having a hydroxyl group is p
-Cresol, resorcinol, pyrogallol, 2,4
-Dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, gallic acid alkyl ester,
7-Hydroxy-2- (2,4-dihydroxyphenyl) -2,4,4-trimethylcucomane, 4b, 5,9
b, 10-Tetrahydro-2,3,7,8-tetrahydroxy-5,10-dimethyl-indene [2,1-a]
-Indene, 5,6,5 ', 6' tetrahydroxy-
3,3,3 ', 3'-tetramethyl-1,1'-spirobiindane, bis (2,4-dihydroxyphenyl) sulfide, 3-methyl-3- (2,4-dihydroxyphenyl) -6-hydroxycumara There are non-etc. These 1,2-naphthoquinonediazide compounds may be used alone or
Used as a mixture of two or more species.

The 1,2-naphthoquinonediazide compound of the present invention is preferably used in an amount of 10 to 50 parts by weight, preferably 20 to 20 parts by weight, based on 100 parts by weight of the novolak resin and the photosensitizer.
It is more preferable to use it in the range of 40 parts by weight. If it is less than 10 parts by weight, the effect of suppressing the dissolution of the alkali-soluble novolac resin is insufficient and the resist pattern is not formed. Further, if the amount exceeds 50 parts by weight, the 1,2-naphthoquinonediazide compound is not completely decomposed by the exposure for a short time which is usually performed, and it becomes difficult to form a resist pattern.

When the positive photoresist composition of the present invention is applied to a substrate such as a silicon wafer, the alkali-soluble novolac resin and the 1,2-naphthoquinonediazide compound are dissolved in a solvent and the solution is applied by a spin coater or the like. To do.

Examples of the solvent used at this time include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate and the like. ..

The positive photoresist composition thus prepared is filtered through a 0.2 μm Teflon filter and applied on a silicon wafer treated with disilazane to a film thickness of about 1.0 μm, and the solvent is removed. Therefore, after drying, it is exposed to ultraviolet rays or deep ultraviolet rays. Next, after exposure, heating is performed, development is performed with an alkali developing solution, and further drying is performed to form a positive resist pattern. Finally, a circuit can be formed by etching this resist pattern with oxygen plasma or the like. Hereinafter, the present invention will be specifically described with reference to examples.

[0026]

EXAMPLE An example of producing an alkali-soluble novolak resin is shown below. Novolac resin 1 m-cresol 1 in a 500 ml separable flask.
08 g, 162 g of p-cresol (m-cresol / p
-Cresol = 40/60 weight ratio), 136 g of 37% formalin and 2 g of oxalic anhydride were charged, the temperature was raised to 96 ° C with stirring, and the reaction was carried out for 2.5 hours. Then 1
The temperature was raised to 80 ° C., dehydration was carried out under normal pressure, the reaction was continued for 1 hour, and then unreacted monomers were removed under reduced pressure.

After that, gel permeation chromatography using acetone as an eluent was carried out to separate by molecular weight to adjust the dispersity to 1.9. The preparative column is a gel pack GL-A130 manufactured by Hitachi Chemical Co., Ltd.
(Inner diameter 40 mm, length 600 mm) was used, and the solvent was acetone and the flow rate was 15 ml / min.

Novolac resin 2 135 g of m-cresol, 135 g of p-cresol (m
-Cresol / p-cresol = 50/50 weight ratio) and 37% formalin 143 g were used, and the same method was used to synthesize Novolak Resin 1. The dispersity is 1.9.

Novolac resin 3 162 g of m-cresol, 108 g of p-cresol (m
-Cresol / p-cresol = 60/40 weight ratio) and 37% formalin 150 g were used in the same manner as in the novolak resin 1. The dispersity is 1.9.

Novolac resin 4 67.5 g of m-cresol, 202.5 of p-cresol
g (m-cresol / p-cresol = 25/75 weight ratio) and 37% formalin 130 g were synthesized in the same manner as in the novolak resin 1. The dispersity is 1.6.

Novolac resin 5 m-cresol 202.5 g, p-cresol 67.5
g (m-cresol / p-cresol = 75/25 weight ratio) and 37% formalin 154 g were synthesized in the same manner as in the novolak resin 1. The dispersity is 1.9.

Examples 1 to 5 and Comparative Examples 1 to 3 The novolak resin, 1,2-naphthoquinonediazide-5sulfonic acid chloride and 7-hydroxy-2- (2,4-dihydroxyphenyl) obtained in the above-mentioned production examples. -2,4
A 1.2: 1 (molar ratio) condensation reaction product of 4-trimethylcucomane was mixed in a ratio as shown in Table 1 and dissolved in ethyl cellosolve acetate to prepare a positive photoresist composition.

This positive photoresist composition was coated on a hexamethyldisilazane-treated silicon wafer with a spin coater to a film thickness of 1.2 μm, and the coating was performed at 90 ° C. for 9 minutes.
After drying for 0 seconds, exposure was performed at a wavelength of 365 nm through a reticle using a reduction projection exposure device. After the exposure, it was dried at 110 ° C. for 90 seconds, developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution, and further dried at 110 ° C. for 90 seconds to obtain a resist pattern. The resolution was determined by observing an electron microscope (SEM) image of this resist pattern, and the heat resistance was 5 at a constant temperature in a pattern of 50 μm.
It was heated for a minute and observed by an SEM photograph to obtain the degree of thermal deformation of the resist pattern. The evaluation results of Examples and Comparative Examples are shown in Table 1. As shown in Table 1, it can be seen that both the resolution and the heat resistance are excellent when the degree of dispersion of the resin of the example is 2.0 or less.

[0034]

[Table 1]

According to the present invention, a positive photoresist composition having excellent resolution and heat resistance can be obtained.

Claims (3)

[Claims] 1. An alkali-soluble novolac resin and 1, 2
In a positive photoresist composition containing a naphthoquinonediazide compound, the alkali-soluble novolac resin is a novolac resin produced by subjecting phenols and formaldehyde to an addition condensation reaction, and is a standard polystyrene determined by gel permeation chromatography. Converted weight average molecular weight is 3000 to 15
Positive photoresist composition having a dispersity of 2.0 or less in the range of 000. 2. The positive photoresist composition according to claim 1, wherein cresols are used as phenols. 3. The cresols are m-cresol and p-.
Consisting of a mixture of cresols and having m-cresol of 30-
The positive photoresist composition according to claim 2, wherein 60% by weight and p-cresol are in the range of 70 to 40% by weight.