JPH03230164A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To enhance resolution, sensitivity, mask fidelity, and heat resistance by preparing a specified novolak compound from a mixture of m-cresol and p-cresol. CONSTITUTION:The resin component to be used is prepared from the mixture of m-cresol and p-cresol in a ratio of 20:80-80:20, and the product contains a novolak dimer in an amount of <=10wt.% ad >=10wt.% novolak trimer represented by formula I in which each of (l) and (n) is 1 or 2; each of m and 0 is an integer of 1-4, but l+m<5, and n+0<5; and R is lower alkyl, halogen, or lower alkoxy. photosensitive agent component contains a compound obtained by esterifying average >=75% hydroxyl groups of tetra-, penta-, or hexa- hydroxybenzophenone with naphthoquinone-1, 2-diazido -4- or -5- sulfonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a positive photoresist composition.
The present invention relates to a positive photoresist that is sensitive to radiation such as molecular beams and is particularly suitable as a resist for manufacturing highly integrated circuits.

[Prior art] As a positive photoresist composition, naphthoquinone-1,2- of polyhydroxybenzophenone is used as a photosensitizer.
Diazide-5-sulfonic acid esters containing novolak made from cresol as a resin component are known.

As integrated circuits become more highly integrated, there is a demand for positive photoresists that have excellent resolution, sensitivity, and good heat resistance, but at present no product that satisfies all performance requirements has yet been obtained.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the various drawbacks of the prior art, and to provide a method that has excellent resolution, sensitivity, and mask fidelity, and has good heat resistance.
An object of the present invention is to provide a positive photoresist composition suitable as a resist for manufacturing highly integrated circuits.

[Means to solve the problem] This object of the present invention is achieved by the following configuration.

1 As a resin component, m-cresol:p-cresol 20/80 to 80/20 (mole ratio) is used as a raw material, and a novolac with a timer content of 10% by weight or less and a trimmer content of 10% by weight or more is used. and on average 75% or more of the hydroxyl groups of tetrahydroxybenzophenone, pentahydroxybenzophenone, or hexahydroxybenzophenone as a photosensitizer component is naphthoquinone-1,2-
Diazide-5-sulfonic acid or naphthoquinone-1,2
- A positive photoresist composition comprising a compound esterified with diazido-4-sulfonic acid.

2 The content of novolac in the timer is 10% by weight or less,
The positive photoresist composition according to the preceding item, characterized in that the composition comprises a novolac and a novolac trimmer, and the trimmer content is 5% by weight or less.

The novolak used in the present invention is primarily produced from a mixture of m-cresol and p-cresol. m
The molar ratio of -cresol and p-cresol at the time of charging the raw materials is 20/80 to 80/20, more preferably 30/70 to 70/30.

In the novolak in the positive photoresist composition of the present invention, it is important that the amount of timer present in the novolak as a low molecular weight component is 10% or less.

Furthermore, it is preferably 7% or less.

Such novolaks are obtained by reacting m-cresol and p-cresol with aldehydes in the presence of an acid catalyst. As the acid catalyst, inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, and perchloric acid, and organic acids such as oxalic acid, formic acid, acetic acid, trifluoroacetic acid, and para-toluenesulfonic acid are used.

Examples of aldehydes include formalin, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, benzaldehyde, phenylacetaldehyde, α-phenylpropionaldehyde, β-phenylpropionaldehyde, 0-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, -chlorobenzaldehyde,
m-chlorobenzaldehyde, p-chlorobenzaldehyde, 0-nitrobenzaldehyde, m-nitrobenzaldehyde, p-nitrobenzaldehyde, 0-methylbenzaldehyde, m-methylbenzaldehyde, p-
Examples include methylbenzaldehyde, p-ethylbenzaldehyde, p-butylbenzaldehyde, and among these, formalin, paraformaldehyde, acetaldehyde, benzaldehyde, and the like are particularly preferred.

These aldehydes may be used alone or in combination of two or more.

Although novolak can be produced without a solvent, it can also be produced in the presence of an organic solvent to increase the reaction rate. Organic solvents used in this case include alcohols such as methanol, ethanol, propatool, butanol, cellosolves such as ethyl cellosolve, methyl cellosolve, and butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, and butyl cellosolve acetate. Preferred are cellosolve esters such as N-methylpyrrolidone and dimethyl sulfoxide, aprotic polar solvents such as N-methylpyrrolidone and dimethyl sulfoxide, esters such as ethyl acetate, propyl acetate and butyl acetate, and ethers such as tetrahydrofuran and dioxane.

Since the novolak thus obtained contains low molecular weight components such as monomers and timers, the following treatment is performed to remove these components.

(1) A method of extracting novolak powder using a poor solvent.

Novolac is finely ground and stirred in a solvent such as benzene, toluene, xylene, chlorobenzene, dichlorobenzene, etc. to extract the low molecular weight portion.

(2) A method in which novolac is dissolved in a good solvent and poured into a poor solvent to reprecipitate it.

Novolac is dissolved in methanol, ethanol, acetone, methyl ethyl ketone, etc., poured into water or water containing the above organic solvent, and the precipitated polymer is filtered off and dried.

(3) A method of dissolving novolak in a good solvent and adding a poor solvent to separate it.

Novolak is dissolved in methanol, ethanol, acetone, methyl ethyl ketone, etc., and a poor solvent such as water, petroleum benzene, petroleum ether, ligroin, n-hexane, etc. is added while stirring to precipitate the high molecular weight portion. After removing the supernatant, the polymer is taken out and dried.

In addition to the above method of removing low molecular weight components using a solvent, a method of thin film distillation under high vacuum can also be adopted.

In order to make the content of the timer 10% by weight or less, 50 to 2%, preferably 30 to 5% of the total low molecular weight components of the novolak should be removed.

This allows the monomer content to be 2% by weight or less. Such treatment also reduces the amount of trimmer in the novolac to approximately 5% by weight or less.

In the present invention, it is important to add a predetermined amount of novolac trimmer to the above novolac so that the total amount of trimmer in the novolac of the resist composition is 10% by weight or more.

That is, since the novolak obtained as described above has a timer content of 10% by weight or less and a trimmer content of 5% by weight or less, a predetermined amount of novolac trimmer prepared separately can be added to the novolak. The total amount of trimmer in the novolak is preferably 10% by weight or more, preferably 40% by weight or less. therefore,
The amount of novolac trimmer added is preferably selected within the range of 5 to 35% by weight.

By adding the novolac trimmer in this way to make the total amount of trimmer in the novolac 10 to 40% by weight, a positive photoresist with excellent sensitivity, resolution, and mask fidelity can be obtained.

If the total amount of trimmer in the novolac is less than 10% by weight, the above-mentioned effects will not be sufficiently enhanced, and if it exceeds 40% by weight, the sensitivity will be high but the heat resistance will be poor.

The novolak used in the present invention has a timer content of 10
% by weight or less, the trimmer content is 10% by weight or more, and the molecular weight distribution is in the range of 3 to 8;
Preferably, the number average molecular weight is in the range of 500 to 5.000.

Here, molecular weight distribution means Mw (weight average molecular weight)/Mn
(number average molecular weight).

The novolac trimmer used in the present invention can be produced by fractionating ordinary novolak, or by reacting phenols with formaldehyde under alkaline conditions or in the presence of divalent metal ions, and then removing excess phenols. A method of reacting under acidic conditions, or 2.
Examples include, but are not limited to, methods for obtaining by reacting 6-bis(hydroxymethyl)phenols and phenols.

In the present invention, the novolac trimmer contained in the novolac is preferably one represented by the following general formula (1).

However, II, n is 1 or 2, m, o are integers from 1 to 4 (however, A'+m<5, n+o<5), R
represents lower alkyl, halogen or lower alkoxy.

R is preferably methyl, ethyl, propyl, isopropyl, chlorine, methoxy, ethoxy, propoxy, isopropoxy, etc., but may also be nitro, cyano, methoxycarbonyl, ethoxycarbonyl, acetyl, phenyl, benzyl, benzoyl, etc. do not have.

Particularly preferred novolac trimmers (1) include those having a structure represented by the following general formula (2).

here, r is one of the following:

H H In addition, R in the above general formula (2) and each of the above structural formulas is each -CH3, C2H5, CA', OCH3 and -0C2H5.

These novolac trimers can be used alone or as a mixture of two or more, but the solubility in a 2.38% tetramethylammonium hydroxide aqueous solution is 2.
It is preferable that it is 00 A/sec or more. Particularly preferred is 500 A to 100 μm/sec.

The dissolution rate can be measured by the following method.

That is, the trimmer is dissolved in an organic solvent such as ethyl cellosolve acetate at a concentration of 10 to 30%, and then coated onto a silicon wafer using a spinner to a thickness of 1 to 5 μm. Next, using a convection oven, the film thickness is measured after prebaking at 100°C for 30 minutes. A silicon wafer is immersed in a 2.38% tetramethylammonium hydroxide aqueous solution at 23° C. for 5 to 30 seconds, and then washed with water. After post-baking at 100° C. for 30 minutes, the film thickness is measured, the amount of film reduction is measured, and the dissolution rate is calculated.

If novolak trimmer cannot be applied alone, or if the dissolution rate is so fast that it is difficult to measure, mix it with other novolacs with known dissolution rates in several proportions and measure the dissolution rate of the mixture.

The dissolution rate is plotted on a logarithmic scale on the vertical axis, the mixing ratio is plotted on a normal scale on the horizontal axis, and the dissolution rate of a single product is determined by extrapolation. Since logarithmic additivity holds for the dissolution rate, a straight line is obtained in the above graph.

That is, the dissolution rate of novolak is R1, and its weight is
, the dissolution rate of the novolac trimmer to be added is R2, its weight is Y1, and the dissolution rate of the mixture is R, then the following formula holds true.

X Log R+ +Y Log R2= (X+Y
) LogRNext, the compound used as the photosensitizer component of the positive photoresist composition of the present invention is tetrahydroxybenzophenone, pentahydroxybenzophenone, or hexahydroxybenzophenone, in which the hydroxyl group in the molecule is on average 75% or more, naphthoquinone-1, It is esterified with 2-diazide-5-sulfonic acid or naphthoquinone-1,2-diazide-4-sulfonic acid, and as a result, a photoresist with good resolution and high heat resistance can be obtained. More preferably, it is 80% or more esterified.

These photosensitizers include, for example, polyhydroxybenzophenone and naphthoquinone-1,2-diazide-5-sulfonyl chloride or naphthoquinone-1°2-diazide-4-sulfonyl chloride in an amount of 0.75 times or more moles or more based on the number of moles of total hydroxyl groups. It can be obtained by reacting in the presence of a base.

Since this reaction has few side reactions, a photosensitizer having an esterification rate substantially equal to the charging ratio of raw materials can be obtained.

As tetrahydroxybenzophenone, 2°3.4
．． 4'-tetrahydroxybenzophenone, 2.4
．． 2',4'-tetrahydroxybenzophenone;
As pentahydroxybenzophenone, 2.3.4
．． 2',4'-pentahydroxybenzophenone/hexahydroxybenzophenone includes 2.3.
4.3',4',5'-hexahydroxybenzophenone is particularly preferably used.

These photosensitizers can be used alone or in combination of two or more in the photoresist composition.

The above resin component and photosensitive agent are dissolved in a suitable organic solvent to form a positive photoresist.

The blending ratio of resin component and photosensitizer is 90/10 to 5 by weight.
0150, more preferably 85/
15 to 70/30. If the amount of photosensitizer is too small, the sensitivity will be high but the heat resistance will be insufficient; if it is too large, the heat resistance will be high but the sensitivity will be low.

In addition to these components, a surfactant to prevent uneven coating during coating, a dye to prevent reflection of light from the substrate, a sensitizer, etc. can be added as appropriate.

The solvent to be used is not particularly limited as long as it dissolves the novolac, photosensitizer, and other components, but glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, methyl cellosolve acetate, and ethyl cellosolve acetate are used. Cellosolve esters such as tart, propylene glycol monoether acetates such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, monohydroxy carboxylic acids such as methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate Esters, toluene, xylene,
Aromatic hydrocarbons such as chlorobenzene, ketones such as methyl isobutyl ketone, methyl isoamyl ketone, cyclohexanone, or ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, t-butyl acetate, ethyl propionate, propyl propionate , isopropyl propionate, butyl propionate, isobutyl propionate, t-butyl propionate, pentyl propionate, and other esters. In addition, if necessary, ethers such as anisole, benzyl ethyl ether, dihexyl ether, diethylene glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 1-
Alcohols such as octatool, 1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate, diethyl oxalate, diethyl maleate, diethyl fumarate, γ-butyrolactone, diethyl carbonate, ethylene carbonate,
Esters such as propylene carbonate, aprotic polar solvents such as dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, etc. can be added.

When using the positive photoresist according to the present invention to fabricate fine nozzles, it is preferable to heat the substrate after exposure and before development (post-exposure bake). can be obtained.

The heating method is not particularly limited, and examples thereof include methods using an oven, a hot plate, and the like. The temperature is preferably in the range of 90 to 140'C, more preferably 1
00-130'C. The heating time is in the range of 1 to 60 minutes, preferably 5 to 30 minutes when using a circulating oven, and 0.5 to 5 minutes, preferably 0.7 to 2 minutes when using a hot plate. be.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to obtain a positive photoresist composition that has excellent resolution, sensitivity, and mask fidelity and is suitable as a resist for manufacturing highly integrated circuits. Further, according to the present invention, a pattern with good contrast without generating scum during development can be reliably obtained.

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto.

In addition, the content of die 7 and trimmer in the present invention is as follows:
Each was determined from a chromatogram measured by gel permeation chromatography (GPC). Furthermore, in the following explanation, "parts" is an abbreviation for parts by weight.

Synthesis Example 1 A novolak resin was obtained from 35 parts of m-cresol, 65 parts of p-cresol, 0.5 part of oxalic acid, and 46 parts of 37% formalin in a conventional manner.

This novolac had a weight average molecular weight of 6,650, a number average molecular weight of 1,184, and a molecular weight distribution of 5.62, and the amount of die 7 was 10.5% by weight and the amount of trimmer was 5.7% by weight. (This novolak is referred to as Novolak A).

One part of Novolak A was taken and dissolved in 5.00 parts of methanol, and 4,00 parts of water was added dropwise while stirring to precipitate Novolak. The supernatant liquid was removed, and the precipitated novolak was taken out and vacuum-dried at 50° C. for 24 hours. 0.86 parts of novolak was obtained, and the weight average molecular weight of this novolak was 7.
259, number average molecular weight is 1,745, molecular weight distribution is 4.
16. The amount of timer was 6.1% by weight, and the amount of trimmer was 3.0% by weight (this novolac is referred to as Novolac B).

Take 1 part of Novolak A and add 5 parts of methanol. 00 parts, and 2.66 parts of water was added dropwise while stirring to precipitate the novolak. The supernatant was removed, and the precipitated novolac was taken out and vacuum-dried at 50'C for 24 hours. 0.82 parts of novolac was obtained, the weight average molecular weight of this novolak was 8,075, the number average molecular weight was 2,037, the molecular weight distribution was 3.96, the content of die 7 was 4.3% by weight, and the trimer content was The amount was 2.1% by weight (this novolak is referred to as Novolak C).

Example 1 818.72 parts of novolak, 2.08 parts of 2,6-bis(2-hydroxy-5-methylphenylmethyl)-4-methylphenol, and 2,3°4.4'-tetrahydroxybenzophenone on average 5.2 parts of a photosensitizer esterified with 3,8 molar equivalents of naphthoquinone-1,2-diazide-5-sulfonic acid, "Troisol" 366 (T
.

ROY CHEMICAL surfactant) 0゜05
1 part was dissolved in 51.8 parts of propylene glycol monomethyl ether acetate and 22.2 parts of ethyl raftate to prepare a resist solution. The content of Dai 7 in the novolak component was 5.5% by weight, and the total amount of trimmer was 12.7% by weight.

This resist solution was filtered through a 0.2 μm membrane filter.
After filtering with
Prebaking was performed for a minute to obtain a resist film with a thickness of 1.16 μm.

Next, the g-ray stepper (-Nippon Optical Tank N5R150506
After exposing the test pattern using E, NA=0.54), post-exposure baking was performed at 110° C. for 1 minute on a hot plate.

Paddle development was performed at 23°C for 1 minute using a 2.38% aqueous solution of tetramethylammonium hydroxide, and after washing with water,
Spin dry.

When the obtained resist pattern was evaluated using a scanning electron microscope, it was found that the exposure amount of 200 mJ/am2 was 0. 50.
0. 45. 0. 42 and 0.40 μm lines and spaces were resolved at a ratio of 1:1. That is, a mask fidelity of up to 0.40 μm was obtained. Also, the contrast (γ value) measured from the sensitivity curve was 3.5.
It was 1.

Comparative Example 1 Above (7)/20.80 parts of Borac A, 2.3°4.4
'-Tetrahydroxybenzophenone is on average 3.
5.20 parts of an 8 molar equivalent esterified photosensitizer and 3660.05 parts of "Troysol" were dissolved in 51.80 parts of propylene glycol monomethyl ether acetate and 22.2 parts of ethyl raftate to prepare a resist solution. .

Add this resist solution to 0. The resultant was filtered through a 2 μm membrane filter, spin-coated onto a 6-inch silicon wafer using a spinner, and prebaked on a hot plate at 90° C. for 1 minute to obtain a resist film with a thickness of 1.16 μm.

Next, a test pattern was exposed using the G-line stepper, and then post-exposure baking was performed on a hot plate for 1 minute at 110°. Paddle development was performed at 23° C. for 1 minute using a 2.38% aqueous solution of tetramethylammonium hydroxide, washed with water, and then spin-dried.

When the obtained resist pattern was evaluated with a scanning electron microscope, it was found to be 0.50 μm at an exposure dose of 200 mJ/cm2.
lines and spaces were resolved at a ratio of 1:1, but patterns smaller than that had a lot of scum and good patterns could not be obtained.

Moreover, the mask fidelity was up to 0.50 μm.

The contrast (γ value) measured from the sensitivity curve is 3°13
Met.

Examples 2 to 11, Comparative Examples 2 to 4 Resist composition solutions were prepared in the same manner as in Example 1, except that the compositions and conditions shown in Table 1 were employed, and evaluated in the same manner. The results are shown in Table 1.

In addition, Novolac trimmer I described in Table 1.

(2), (2) and (2) have the chemical structures and dissolution rates (A/sec) shown below, respectively.

Number Structural formula Dissolution rate Also, In Table 1, photosensitizer a1 1 C and d are Each has the following chemical structure.

a: 2.3.4.4'-tetrahydroxybenzophenone is on average naphthoquinone-1°2-diazide-5
- Compound b 2.3.4.4' -Tet-rahydroxybenzophenone esterified with 3°8 molar equivalents of sulfonic acid is on average naphthoquinone-1°2-diazide-5
Compound c esterified with 3.5 molar equivalents of naphthoquinone 1.2-diazide-5-sulfonic acid: 2.3,4.2',4'-pentahytomixibenzophenone esterified with 3.5 molar equivalents of naphthoquinone 1.2-diazido-5-sulfonic acid. 0 molar equivalent esterified compound d: 2.3,4.3',4',5'-hexahydroxybenzophenone on average becomes naphthoquinone-
Compound esterified with 4.8 molar equivalents of 1,2-diazido-5-sulfonic acid

Claims (1)

[Claims] 1. As a resin component, m-cresol: p-cresol 20/80 to 80/20 (mole ratio) is used as a raw material, the timer content is 10% by weight or less, and the trimmer content is 10% by weight or less. %
Contains novolak in an amount greater than or equal to the weight of the photosensitive agent, and an average of 75% or more of the hydroxyl groups of tetrahydroxybenzophenone, pentahydroxybenzophenone, or hexahydroxybenzophenone as a photosensitizer component is naphthoquinone-1,2-
Diazido-5-sulfonic acid or naphthoquinone-1,2
- A positive photoresist composition comprising a compound esterified with diazido-4-sulfonic acid. 2 The content of novolac in the timer is 10% by weight or less,
2. The positive-working photoresist composition according to claim 1, comprising a novolac and a novolac trimmer in which the trimmer content is 5% by weight or less. 3. The positive photoresist composition according to claim 2, wherein the novolac trimmer is a trimmer represented by the following general formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) However, l and n are 1 or 2, m and o are integers from 1 to 4 (
However, l+m<5, n+o<5), R is lower alkyl,
Indicates halogen or lower alkoxy. 4 The dissolution rate of novolac trimer in a 2.38% tetramethylammonium hydroxide aqueous solution is 200 Å
4. The positive photoresist composition according to claim 2, wherein the photoresist composition has a photoresist composition of at least 1/sec.