JP2961947B2 - Positive resist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive resist composition excellent in sensitivity, residual film ratio and heat resistance.

[0002]

2. Description of the Related Art A resist composition containing a compound having a quinonediazide group as a radiation-sensitive agent can be converted from an alkali-insoluble state to an alkali-soluble state by irradiation with light having a wavelength of 500 nm or less, whereby the quinonediazide group is decomposed to generate a carboxyl group. Utilizing this, it is used as a positive resist. This positive resist has a feature that it has better resolution than a negative resist, and is used for manufacturing integrated circuits such as ICs and LSIs.

In recent years, integrated circuits have been miniaturized due to high integration, and submicron pattern formation has now been required. Therefore, it is said that a limit of 2 μm is used for a mask contact method conventionally used for forming an integrated circuit, but instead, a reduced projection exposure method has attracted attention. This system is a system in which a pattern of a master mask (reticle) is reduced and projected by a lens system and exposed, and it is said that the resolving power can be down to submicron. However, in the reduced projection exposure method, since repetitive division exposure is performed, there is a problem that the total exposure time per wafer becomes long.

As a method of solving this, it is most important to improve the sensitivity of the resist used, as well as to improve the apparatus. To increase the sensitivity of the resist, for example, there is a method of reducing the molecular weight of the alkali-soluble resin as a component. However, generally, as the molecular weight of the alkali-soluble resin decreases, the heat resistance of the resist deteriorates. As another means of increasing the sensitivity, it is conceivable to increase the dissolution rate in an alkali developing solution by selecting a monomer of an alkali-soluble resin to increase the sensitivity of the resist. For example, in a novolak resin, when the ratio of a monomer having high solubility in an alkali developer such as metacresol or phenol is increased, the dissolution rate of the resin in the alkali developer is increased. However, even if high sensitivity is achieved without lowering the heat resistance by this method, that is, without lowering the molecular weight of the alkali-soluble resin, the residual film ratio is generally reduced and the resolution is significantly reduced. As described above, in general, sensitivity, heat resistance, and residual film ratio tend to be in conflict with each other, and in general, when one of them is to be improved, the other deteriorates.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a positive resist composition having excellent heat resistance without impairing sensitivity and residual film ratio.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a novolak resin obtained by condensing a compound having a specific phenolic hydroxyl group with an aldehyde is used as an alkali-soluble resin for a positive resist composition. When they were used, they found that heat resistance could be remarkably improved without impairing the sensitivity and the residual film ratio, and completed the present invention.

That is, the present invention comprises a radiation-sensitive compound and an alkali-soluble resin, wherein the alkali-soluble resin is represented by the following general formula (I):

[0008]

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(Wherein, R _{1 to} R ₉ each independently represent an alkyl group, a hydrogen atom, a halogen atom, or an —OH group, and at least one of R _{1 to} R ₉ is an —OH group; At least two of the o-position and the p-position relative to the OH group are hydrogen atoms) and an aldehyde and a novolak resin-containing positive resist composition. .

Hereinafter, the positive resist composition of the present invention will be described in more detail. The novolak resin used in the present invention is obtained by condensing the compound of the general formula (I) with an aldehyde. The compound of the general formula (I) includes m-isopropenylphenol or a nucleus-substituted product thereof, p-isopropenylphenol or a nucleus-substituted product thereof,
And one or two of these linear dimers,
It can be synthesized by the method described in US Pat. No. 3,288,864. In the general formula (I), examples of the alkyl group represented by R _{1 to} R ₉ include linear or branched ones having 1 to 7 carbon atoms, and among them, a methyl group or an ethyl group is preferable. As the halogen atom, fluorine,
Chlorine, bromine and iodine.

Specific examples of the compound of the general formula (I) are as follows. In the production of novolak resins, these can be used alone or in combination.

[0012]

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Examples of the aldehyde used in the condensation reaction with the compound represented by the general formula (I) include formaldehyde, paraformaldehyde, acetaldehyde, propylaldehyde, benzaldehyde, phenylacetaldehyde, α-phenylpropylaldehyde,
β-phenylpropyl aldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-
Examples include hydroxybenzaldehyde, glutaraldehyde, glyoxal, o-methylbenzaldehyde, p-methylbenzaldehyde and the like. Of these, formaldehyde is particularly preferred in that it is industrially available. Each of these aldehydes alone,
Alternatively, two or more kinds can be used in combination.

The condensation reaction between the compound of the formula (I) and aldehydes can be carried out according to a conventional method. This condensation reaction is usually carried out in the presence of an acid catalyst at 60 to 120 ° C for 2 to 3 times.
Performed for 0 hours. As the acid catalyst, an organic acid, an inorganic acid, a divalent metal salt or the like is used. Specific examples of the catalyst include oxalic acid, hydrochloric acid, sulfuric acid, perchloric acid, p-toluenesulfonic acid, trichloroacetic acid, phosphoric acid, formic acid, zinc acetate, magnesium acetate and the like. In addition, the reaction may be performed in bulk or using an appropriate solvent.

The novolak resin thus obtained has a polystyrene-equivalent weight average molecular weight (M) determined by gel permeation chromatography (hereinafter referred to as GPC).
Suitably, w) is in the range 2,000-50,000, more preferably in the range 3,000-30,000. The resist composition of the present invention must contain, as an alkali-soluble resin, a novolak resin obtained by condensing a compound of the general formula (I) with an aldehyde. Of course, a mixture of a novolak resin obtained by condensing a phenol compound other than (I) and an aldehyde may be used.

As the radiation-sensitive compound which is another component of the resist composition, a quinonediazide compound or the like is used. This quinonediazide compound can be obtained by a known method,
For example, it can be obtained by condensing a naphthoquinonediazidesulfonic acid halide or a benzoquinonediazidesulfonic acid halide with a compound having a hydroxyl group in the presence of a weak alkali.

Examples of the compound having a hydroxyl group used herein include hydroquinone, resorcin, phloroglucin, 2,4-dihydroxybenzophenone, and the like, as well as 2,3,4-trihydroxybenzophenone,
2 ', 3-trihydroxybenzophenone, 2,2',
4-trihydroxybenzophenone, 2,2 ', 5-trihydroxybenzophenone, 2,3,3'-trihydroxybenzophenone, 2,3,4'-trihydroxybenzophenone, 2,3', 4-trihydroxybenzophenone, 2,3 ', 5-trihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone,
2,4 ', 5-trihydroxybenzophenone, 2',
3,4-trihydroxybenzophenone, 3,3 ', 4
Trihydroxybenzophenones such as -trihydroxybenzophenone, 3,4,4'-trihydroxybenzophenone, 2,3,3 ', 4-tetrahydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, 2, 2 ', 4,4'-tetrahydroxybenzophenone, 2,2', 3,4-tetrahydroxybenzophenone, 2,2 ', 3,4'-tetrahydroxybenzophenone, 2,2', 5,5'-tetra Tetrahydroxybenzophenones such as hydroxybenzophenone, 2,3 ', 4', 5-tetrahydroxybenzophenone and 2,3 ', 5,5'-tetrahydroxybenzophenone, 2,2', 3,4,4'-pentane Hydroxybenzophenone, 2,2 ', 3,4,5'-pentahydroxybenzophen Non, 2,2 ', 3,3', 4-
Pentahydroxybenzophenone, 2,3,3 ', 4
Pentahydroxybenzophenones such as 5'-pentahydroxybenzophenone, 2,3,3 ', 4,4',
5'-hexahydroxybenzophenone, 2,2 ',
Hexahydroxybenzophenones such as 3,3 ', 4,5'-hexahydroxybenzophenone;

[0018]

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(Where q represents a number from 0 to 4;
Represents a number of 1 or more and 5 or less, q + r is 2 or more, and R
₁₀ , R ₁₁ and R ₁₂ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a cyclohexyl group or an aryl group), and alkyl gallate esters.

The preparation of a positive resist solution is carried out by mixing and dissolving a radiation-sensitive compound and an alkali-soluble resin in a solvent. The weight ratio of the alkali-soluble resin to the quinonediazide compound is preferably in the range of 1: 1 to 6: 1.

The solvent to be used preferably has an appropriate drying rate and gives a uniform and smooth coating film by evaporation of the solvent. Examples of such a solvent include ethyl cellosolve acetate, methyl cellosolve acetate, ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether acetate, butyl acetate, methyl isobutyl ketone, xylene, ethyl lactate, and propylene glycol monoethyl ether acetate. For example, when ethyl cellosolve acetate is used as a solvent, the amount of the solvent is 30 to 80 with respect to the total amount of the composition containing the solvent.
% By weight. The resist composition obtained as described above may further contain a small amount of a resin or a dye as an additive, if necessary.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The percentages and parts in the examples are on a weight basis.

Synthesis Example 1 The following formula (1) was placed in a four-necked flask having an inner volume of 300 ml.

[0024]

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53.6 g of the compound (p-OST cyclic dimer, manufactured by Mitsui Toatsu Chemicals, Inc.), 50.4 g of ethyl cellosolve acetate, and 6.0% of a 5% oxalic acid aqueous solution.
After charging 8 g, the temperature was raised to 80 ° C., and 13.0 g of 37% formalin was added dropwise from the dropping funnel over 60 minutes with stirring.
After stirring at 110 ° C. for 10 hours, neutralization, washing with water,
After dehydration, an ethyl cellosolve acetate solution of the novolak resin was obtained. This resin is referred to as novolak resin A. G
The weight average molecular weight (in terms of polystyrene) of the novolak resin A measured by PC was 5,500.

EXAMPLES AND COMPARATIVE EXAMPLES Novolak resin A obtained in Synthesis Example 1 and novolak resins B and C shown below for comparison were used, and a quinonediazide compound shown below was used as a radiation-sensitive compound. The example which prepared and evaluated the thing is shown.

Novolak resin B: meta-cresol / para-cresol = 70/30, cresol / formalin =
A weight average molecular weight of 12,000 obtained by reacting under reflux with an oxalic acid catalyst at a molar ratio of 1 / 0.8.
Novolak resin (polystyrene equivalent). Novolak resin C: meta-cresol / para-cresol = 60/40, cresol / formalin = 1 / 0.8 in molar ratio, using an oxalic acid catalyst under reflux to obtain a weight average molecular weight of 7,000 ( Novolak resin (polystyrene equivalent). Quinonediazide compound: a phenolic compound of the following formula (2,4,4-trimethyl-2 ', 4', 7-trihydroxyflavan) and naphthoquinone- (1,2) -diazide- (2) -5-sulfonic acid chloride In a molar ratio of 1: 2.4.

[0028]

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The novolak resin and the quinonediazide compound were prepared in the composition shown in Table 1 with ethyl cellosolve acetate 48.
Dissolves in the part. This solution was filtered through a 0.2 μm Teflon filter to prepare a resist solution. This was applied to a 1.3 μm thick silicon wafer that had been washed by a conventional method using a spin coater. Next, the silicon wafer was baked on a hot plate at 100 ° C. for 60 seconds. Next, a reduced projection exposure machine (Nikon NSR 1505) having an exposure wavelength of 436 nm (g-line) was added to the wafer.
G3C, NA = 0.42), and the exposure was changed stepwise. This was developed with a developer SOPD manufactured by Sumitomo Chemical Co., Ltd. for 1 minute to obtain a positive pattern.

Then, the remaining film thickness of the resist was plotted against the exposure amount, and the minimum exposure amount necessary for the resist film thickness to become 0 was defined as the sensitivity. Further, the remaining film ratio was determined from the film thickness before exposure and the film thickness of the portion remaining as a pattern after development. Further, the wafer on which the resist pattern is formed is heated at a predetermined temperature for 3 minutes on a direct hot plate,
The presence or absence of thermal deformation of the 3 μm line-and-space pattern was observed with a scanning electron microscope, and the heat resistance was evaluated at the temperature at which the line-and-space pattern began to thermally deform. The results are shown in Table 1 together with the composition of the resist.

[0031]

[Table 1]

[0032]

The positive resist composition of the present invention is excellent in sensitivity, heat resistance and residual film ratio. This composition has g
It can be used not only for line exposure and i-line exposure but also for KrF excimer laser exposure.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-289947 (JP, A) JP-A-61-97278 (JP, A) JP-A-62-24241 (JP, A) JP-A-4- 230754 (JP, A) JP-A-3-279959 (JP, A) JP-A-3-2155862 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 7/023 511 C08L 61/06

Claims (1)

(57) [Claims] 1. A compound represented by the following general formula (I ) : (Wherein each of R ₁ to R ₉ independently represent an alkyl group, a hydrogen atom, represents a halogen atom or a -OH group, R ₁ to R ₉
One even without least of an -OH group, Oh at least two of the hydrogen atoms of the o-position and p-position to the -OH group
) And an aldehyde.
Containing novolak resin and radiation-sensitive compound
A positive resist composition comprising: