JP3458385B2 - Method for producing novolak resin and positive resist composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a novolak resin by condensing phenols and aldehydes, and more particularly to a method for producing a novolak resin suitable for use in a resist .

[0002]

2. Description of the Related Art In recent years, integrated circuits have become finer with higher integration, and nowadays, submicron pattern formation is required, and a positive resist having excellent resolution is demanded. Conventionally, a mask contact method has been used to form an integrated circuit, but this method has a limit of 2 μm. Instead, a reduction projection exposure method is used especially for forming a large-scale integrated circuit (LSI). Is used proactively.

This system is a master mask (reticle)
The pattern is exposed by reducing and projecting the pattern with a lens system, and the resolution can be up to submicron. However, one of the problems in this reduction projection exposure method is that the throughput is low. That is, unlike the conventional batch exposure method such as the mask contact method, the reduced projection exposure method uses divided and repeated exposure, and thus the total exposure time per wafer becomes long.

As a method for solving this, it is most important to improve the sensitivity of the resist used as well as to improve the apparatus. Through higher sensitivity, throughput can be improved, and yield can be improved. In general, positive resists have lower sensitivity than negative resists and are desired to be improved.

On the other hand, as the degree of integration of LSI has improved and wiring has become finer, dry etching has become mainstream instead of conventional wet etching. Due to this dry etching, the heat resistance of the resist is required more than ever.

[0006]

Looking at the positive resists currently used from this point of view, the sensitivity, resolution,
It is not always satisfactory in terms of heat resistance and residual film rate, and there is an inconvenient situation in that when one property is improved, another property is deteriorated.

For example, in order to increase the sensitivity of the resist, there is a method of lowering the molecular weight of the novolak resin used for the positive type resist, which increases the dissolution rate in an alkali developing solution, so that the apparent resist The sensitivity goes up. However, in this method, the film slippage becomes very large (reduction of the residual film rate), the pattern shape is deteriorated, and the difference in the dissolution rate between the exposed portion and the unexposed portion with respect to the developing solution becomes small. In addition to the problem of so-called reduction of γ value (decrease of resolution), there is a very serious inconvenience that the heat resistance of the resist is reduced.

The object of the present invention is to solve the above-mentioned problems of the prior art and to produce a positive resist composition having excellent balance of sensitivity, resolution, heat resistance and residual film rate for the production of integrated circuits .
And to provide a manufacturing method suitable novolak resins for use in.

[0009]

That is, the present invention is a method for producing a novolak resin by reacting phenols and aldehydes in the presence of an acid catalyst, and water, acetone, methyl ethyl ketone, methyl isobutyl ketone as a solvent, Diisobutyl ketone, toluene, methanol,
Ethanol, n-propanol, iso-propanol,
n-butanol, n-pentanol, cyclohexanone, 2-heptanone, 3-heptanone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, dioxane, 3-methoxybutanol or dimethylformamide. In an amount of 0.27 to 1.30 mol with respect to 1 mol of the phenols, and an acid catalyst with a pKa of less than 3 with respect to 1 mol of the phenols in an amount of 0.005 to 1 mol of the phenols.
The present invention provides a method for producing a novolac resin, which is characterized by using 2 to 0.1 mol .

The present invention will be described in more detail below. Examples of the phenols used for producing the novolac resin include phenol, m-cresol, p-cresol, o-cresol, xylenol, trimethylphenol, p-sec-butylphenol, p-tert-butylphenol, p-tert-amyl. Phenol, 2-tert
-Butyl-4-methyl-phenol, catechol, resorcin, p-phenylphenol, bisphenol A,
And mixtures thereof, and the like. Among these, m-cresol, p-cresol, 2-tert-
Butyl-5-methylphenol, 2,3,5-trimethylphenol or mixtures thereof are particularly preferred.

Examples of the aldehydes used for producing the novolac resin include formaldehyde, paraformaldehyde, acetaldehyde, crotonaldehyde, benzaldehyde, salicylaldehyde, m-hydroxybenzaldehyde, p-hydroxybenzaldehyde, terephthalaldehyde, acrolein, glyoxal and the like. Of these, formaldehyde is particularly preferable. These aldehydes can be used alone or in admixture of two or more.
The amount of aldehydes used is based on 1 mol of phenols.
It is preferably 0.2 to 2 mol, more preferably 0.5 to 1 mol.

In the present invention, when the novolac resin is produced by reacting phenols and aldehydes, p
An acid catalyst having a Ka of 3 to 5 is used. Examples of such an acid catalyst include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, formic acid and lactic acid, and of these, acetic acid is particularly preferable. The acid catalyst having a pKa of 3 to 5 has a pH of 0. It is used in the range of 27 to 1.30 mol. When the amount of the acid catalyst is too small, the reaction time becomes long, and when the resulting novolac resin is applied to a positive resist, heat resistance and resolution are not improved. On the other hand, if the amount is too large,
The catalyst may remain after the obtained novolac resin is washed, which is not preferable.

In the present invention, in addition to the acid catalyst having a pKa of 3 to 5, an acid catalyst having a pKa of less than 3 is used in combination.
Examples of such an acid catalyst having a pKa of less than 3 include oxalic acid, hydrochloric acid, perchloric acid, sulfuric acid, p-toluenesulfonic acid,
Mention may be made of trichloroacetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and mixtures thereof. When an acid catalyst having a pKa of less than 3 is used in addition to the acid catalyst having a pKa of 3 to 5, the amount of the latter is 1
It is 0.002-0.1 mol with respect to mol.

The method of the present invention comprises reacting phenols and aldehydes in the presence of a specific acid catalyst,
Other reaction conditions can be appropriately selected from the general range. For example, the reaction temperature can be appropriately adjusted and is preferably 80 to 200 ° C.

[0015] The reaction of phenols and aldehydes Nau lines using solvent <br/> agent. It is a solvent, water, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, toluene, methanol, ethanol, n- propanol, iso- propanol, n- butanol, n
-Pentanol, cyclohexanone, 2-heptanone,
3-heptanone, ethylene glycol methyl ether,
Ethylene glycol ethyl ether, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, dioxane, 3-methoxybutanol or dimethylformamide. Of these, methyl isobutyl ketone or ethylene glycol ethyl ether acetate is particularly preferable. of course,
You may mix and use 2 or more types of solvents. The amount of soluble agent,
The amount is 10 to 1,000 parts by weight, preferably 30 to 500 parts by weight, based on 100 parts by weight of phenols.

Examples of the method for charging the reaction raw materials such as phenols, aldehydes and acid catalysts include a method of charging them all at once and a method of adding a part or all of them as the reaction progresses. You can

After completion of the reaction, it is preferable to wash with water and dehydrate to remove the acid catalyst and metal components contained in the novolac resin. If necessary, it is also effective to carry out an operation such as fractionation to remove low molecular weight components and narrow the molecular weight distribution.

The novolak resin thus obtained is preferably used in a radiation sensitive resin composition such as a positive resist composition. The positive resist composition contains a novolac resin and a radiation sensitive compound.

A quinonediazide compound or the like is used as the radiation-sensitive compound in the positive resist composition. This quinonediazide compound can be obtained by a known method, for example, 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 for producing the radiation-sensitive quinonediazide compound include hydroquinone, resorcin, phloroglucin, alkyl gallate, 2,4-dihydroxybenzophenone, and further 2,3,4- Trihydroxybenzophenone, 2,2 ', 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-trihydroxybenzophenone,
Trihydroxybenzophenones such as 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'-tetrahydroxybenzophenone, 2,3 ',
4 ', 5-tetrahydroxybenzophenone, 2,
Tetrahydroxybenzophenones such as 3 ', 5,5'-tetrahydroxybenzophenone, 2,2', 3,
4,4'-pentahydroxybenzophenone, 2,
Pentahydroxy such as 2 ', 3,4,5'-pentahydroxybenzophenone, 2,2', 3,3 ', 4, -pentahydroxybenzophenone, 2,3,3', 4,5'-pentahydroxybenzophenone Hexahydroxybenzophenones such as benzophenones, 2,3,3 ', 4,4', 5'-hexahydroxybenzophenone, 2,2 ', 3,3', 4,5'-hexahydroxybenzophenone, formula

[0021]

[Chemical 1]

(Where p is a number from 0 to 4 and q
Represents a number of 1 or more and 5 or less, p + q is 2 or more, and R
_{1 to} R ₃ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a cyclohexyl group or an aryl group. Aromatic hydroxyl compounds such as oxyflavans represented by

The positive resist solution is prepared by mixing and dissolving the novolac resin and the radiation-sensitive compound in a solvent. The weight ratio of the novolac resin to the radiation-sensitive compound is preferably in the range of 1: 1 to 6: 1.

The solvent used is preferably one which has an appropriate drying rate and evaporates the solvent to give a uniform and smooth coating film. 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. When ethyl cellosolve acetate is used as the solvent, the amount of the solvent is preferably 30 to 80% by weight based on the total weight of the composition. The resist composition obtained by the above method may further contain a small amount of a resin or dye as an additive, if necessary.

[0025]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. In addition,% and parts are based on weight unless otherwise specified. Further, the indications in parentheses in Synthesis Example 1 correspond to the item names in Table 1 described later.

Synthesis Example 1 (Invention) In a four-necked flask equipped with a reflux condenser, a thermometer, a stirrer and a dropping funnel, the following raw materials were placed and dissolved.

[0027] m-cresol 316.0g p-cresol 170.6 g Glacial acetic acid (acid catalyst 1) 223.0g 10% oxalic acid water (acid catalyst 2) 82.1g Methyl isobutyl ketone (reaction solvent) 453.6g [Hereinafter, referred to as MIBK]

The mixture was heated to 90 ° C., 209.8 g of 37% formalin was added dropwise over 1 hour, and then heated at reflux temperature for 8 hours (reaction time). The obtained reaction mixture was washed with water, dehydrated, and MIBK (diluting solvent) was further added to dilute it to a concentration of 15% (dilution ratio). After taking 500 g (amount of diluted resin solution) of the diluted resin solution, 384.5 g of n-heptane was added thereto, and the mixture was stirred while keeping the temperature at 60 ° C., allowed to stand, and separated. Ethyl lactate 400 was added to the obtained resin solution.
g was added and the mixture was concentrated to obtain a solution of novolak resin. The solid content of novolac resin in this solution was 35%. The raw material charging amounts and conditions in this reaction are summarized in Table 1.

Synthesis Examples 2-6 (invention) and 7-10
(Comparison) According to Synthesis Example 1, synthesis was performed under the conditions shown in Tables 1 to 3 to obtain each novolac resin.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Synthesis Example 11 (Production of Resist Additive) 50 equipped with a stirrer, cooling pipe, water separator and thermometer
In a 0 ml three-necked flask, 2,6-xylenol 134.0
g, salicylaldehyde 33.7 g, p-toluenesulfonic acid 0.83 g and toluene 268 g were charged, and the mixture was reacted in an oil bath with heating and stirring at 115 ° C. for 16 hours while removing condensed water. The reaction mixture was filtered at 50 to 60 ° C. to obtain a crude cake of the compound represented by the following formula (a).

[0034]

[Chemical 2]

20 g of this crude cake was added to 580 g of methanol.
After being dissolved at -25 ° C, charged with 1,450 g of ion-exchanged water, filtered, and dried to give a purified cake 89.3.
g was obtained (yield based on salicylaldehyde 93.0
%). This is designated as compound a.

Synthesis Example 12 (Production of Another Resist Additive) The same procedure as in Synthesis Example 11 was repeated except that 2,5-xylenol was used instead of 2,6-xylenol.
A compound represented by (hereinafter, referred to as compound b) was synthesized.

[0037]

[Chemical 3]

Examples 1 to 6 and Comparative Examples 1 to 4 Novolak resins obtained as in Synthesis Examples 1 to 10, compound a or compound b obtained as in Synthesis Examples 11 or 12, and radiation-sensitive compounds. Was dissolved in ethyl lactate with the compositions shown in Tables 4 and 5 and filtered through a Teflon membrane filter (pore size 0.2 μm) to prepare a positive resist composition. This was applied to a silicon wafer that had been washed by a conventional method using a spin coater at 4,000 rp.
applied at m. Then, this silicon wafer is
Baking was performed on a vacuum adsorption type hot plate at 0 ° C. for 1 minute.
After that, an i-line (365 nm) reduction projection exposure apparatus LD 5010i manufactured by Hitachi Ltd. was used to perform exposure by changing the exposure time step by step for each shot. Further development, rinsing and drying were carried out to obtain a positive pattern.

With respect to the obtained positive type pattern, the film reduction amount and the exposure time of each shot were plotted to determine the sensitivity. Further, the residual film rate was obtained from the residual film thickness of the unexposed portion. Furthermore, the silicon wafer with the developed resist pattern was left in a clean oven set to various temperatures for 30 minutes in an air atmosphere, and then the resist pattern was observed with a scanning electron microscope to obtain heat resistance. Was evaluated. The resolving power was expressed as the minimum line width for resolving lines and spaces.

The results are summarized in Tables 4 and 5 together with the resist composition. As is clear from the table, it was confirmed that the balance of resolution and heat resistance in each composition of the examples was markedly improved as compared with that of the comparative examples.

[0041]

[Table 4]

[0042]

[Table 5]

(Footnotes in Tables 4 and 5) ^* Radiation-sensitive compound c: naphthoquinone- (1,2) -diazide- (2) -5-sulfonic acid chloride and 2,4,4 represented by the following formula -Condensation product with trimethyl-2 ', 4', 7-trihydroxyflavan (average of 2.8 hydroxyl groups esterified).

[0044]

[Chemical 4]

Radiation-sensitive compound d: naphthoquinone- (1,2) -diazide- (2) -5-sulfonic acid chloride and 2,3,4,4 'represented by the following formula
-Condensate with tetrahydroxybenzophenone (average 2.
5 hydroxyl groups are esterified).

[0046]

[Chemical 5]

[0047]

By using the novolac resin obtained by the production method of the present invention, a positive resist composition having an excellent balance of sensitivity, resolution, residual film rate and heat resistance can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yasutoshi Doi, 3-98 Kasugadenaka, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Chemical Co., Ltd. (56) Reference JP-A-2-222409 (JP, A) JP 62-150245 (JP, A) JP 61-55113 (JP, A) JP 61-171773 (JP, A) JP 62-230816 (JP, A) JP 60 -260611 (JP, A) JP 61-12714 (JP, A) JP 62-160444 (JP, A) JP 62-161145 (JP, A) JP 62-161146 (JP, A) ) JP 55-155013 (JP, A) JP 4-202312 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 8/00-8/38 G03F 7 / 023 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. A method for producing a novolak resin by reacting phenols and aldehydes in the presence of an acid catalyst, wherein water, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, toluene, methanol, ethanol, n is used as a solvent. -Propanol, iso
-Propanol, n-butanol, n-pentanol,
Cyclohexanone, 2-heptanone, 3-heptanone,
Ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, dioxane, 3-methoxybutanol or dimethylformamide is allowed to coexist, and an acid catalyst having a pKa of 3 to 5 is added to 1 mol of phenols. On the other hand, a method for producing a novolak resin, which comprises using 0.27 to 1.30 mol and 0.002 to 0.1 mol of an acid catalyst having a pKa of less than 3 with respect to 1 mol of a phenol. 2. The method for producing a novolak resin according to claim 1, wherein the acid catalyst having a pKa of 3 to 5 is acetic acid. 3. The method for producing a novolak resin according to claim 1, wherein the acid catalyst having a pKa of less than 3 is oxalic acid .