JPH0519465A - Pattern forming method - Google Patents

Abstract

PURPOSE:To form a resist pattern with excellent pattern shape and throughput without causing undercut. CONSTITUTION:A resist pattern is formed with a radiation sensitive resin compsn. contg. 1,2-quinonediazidosulfonic ester of novolak resin obtd. by polycondensing a cresol mixture contg. m-cresol and p-cresol with formaldehyde, having 1,000-10,000 weight average mol.wt. (expressed in terms of polystyrene) and contg. >=13wt.% low mol.wt. component having <600mol.wt. (expressed in terms of polystyrene).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method by dry development using oxygen plasma etching.

[0002]

2. Description of the Related Art Conventionally, in the manufacturing process of semiconductor devices such as IC and LSI, a quinonediazide compound is mixed with a negative photoresist or novolac resin in which a bisazide is mixed with a cyclized product of polyisoprene is mixed on a substrate to be processed. Applying a radiation-sensitive resin composition such as a positive photoresist,
Mercury lamp g-line (wavelength 436nm) and i-line (365nm)
A photolithography method is used in which a pattern is formed by exposing the film to light and developing with a developing solution.

However, in recent years, LSIs have become finer,
The minimum size of a pattern to be formed on a substrate is entering a region of 1 μm or less. In such a size region, even if a conventional photolithography method using a developing solution is used, a step structure is particularly formed. When a substrate is used, there is a problem that sufficient resolution cannot be achieved due to the influence of light reflection during exposure and the problem of shallow depth of focus in the exposure system.

As a method for solving such a problem, instead of developing using a developing solution in photolithography, dry development is performed by etching using gas plasma such as anisotropic oxygen plasma to form a resist pattern. It is known how to do it.

In Japanese Patent Laid-Open No. 61-107346, a photosensitive resin layer containing a polymer mixed or combined with a photoactive compound is coated on a substrate, and the layer is visible in the irradiated portion of the layer. When exposed to light or ultraviolet light, the silylating agent has the property of being capable of selectively diffusing to the irradiated portion; exposing the photosensitive resin layer to only selected portions of the layer. Exposing to UV or visible light through a mask that allows;

The photosensitive resin layer is treated with a silylating agent, whereby the silylating agent is selectively absorbed in the irradiated portion of the coating (photosensitive resin layer) and is exposed to the irradiation. React with the part that has

A method for obtaining a desired negative pattern by dry-developing the photosensitive resin layer thus treated by plasma etching to selectively remove the non-irradiated portion is described.

According to this method, since the silylating agent absorbed in the portion irradiated with ultraviolet rays or visible rays has a very high resistance to oxygen plasma, it is possible to obtain a sharpness by etching with oxygen plasma having high anisotropy. It is known that a resist pattern having various side walls can be obtained, and thus a fine pattern can be resolved.

However, recently, when observing the cross-sectional shape after plasma etching, a phenomenon called undercut in which the line width near the central portion is thinner than the line width at the upper portion of the pattern cross section (hereinafter, this phenomenon is referred to as "undercut"). Called)
Has become a problem. When such an undercut occurs, it is difficult to measure the dimension of the part where the resist pattern and the substrate contact without destroying the wafer.Therefore, when processing the underlying substrate using the resist pattern as a protective film, It becomes extremely difficult to predict the dimension of the pattern, and there arises a problem that the reliability and the yield of the performance of the obtained semiconductor element are significantly reduced. Further, in the above-mentioned pattern forming method, since the sensitivity of the conventional radiation-sensitive resin used is low, the exposure time per wafer becomes long, which causes a problem that the exposure throughput decreases.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern forming method. Another object of the present invention is to provide a resist pattern forming method which is free from undercutting and has an excellent pattern shape and throughput. Further objects and advantages of the present invention will be apparent from the following description.

[0011]

According to the present invention, the above objects and advantages of the present invention are obtained by (1). Polycondensing mixed cresol containing m-cresol and p-cresol with formaldehyde. And polystyrene-reduced weight average molecular weight (hereinafter, “Mw”)
Is 1,000 to 10,000 and a polystyrene-equivalent molecular weight of less than 600 is 13
A layer of a radiation-sensitive resin composition containing a 1,2-quinonediazide sulfonic acid ester of a novolac resin, which is contained in an amount of at least wt.

(2). Irradiate only selected portions with radiation, and (3). Treat with vapor of silylating agent to selectively absorb the silylating agent in the radiation-exposed portion to react, and (4). ). The resist pattern formation method is characterized in that the layer is dry-developed by anisotropic oxygen plasma etching to selectively remove the non-irradiated portion of the layer.

One of the novolac resins used in the present invention,
The 2-quinonediazidesulfonic acid ester is obtained by condensing a novolak resin and 1,2-quinonediazidesulfonyl halide in the presence of a basic catalyst in a suitable condensation solvent.

Here, the novolac resin is synthesized by condensing mixed cresol containing m-cresol and p-cresol as main components and formaldehyde under an acid catalyst. At that time, m-cresol and p-cresol may be mixed with formaldehyde in advance in a mixed state, or may be separately mixed with formaldehyde and combined in the reaction system. It should be understood that both cases fall within the scope of mixed cresols.

The proportion of m-cresol in the mixed cresol is preferably 40 to 90% by weight, more preferably 50 to 80% by weight. The proportion of p-cresol is preferably 10 to 60% by weight, more preferably 20 to 50% by weight. When the proportion of m-cresol is less than 40% by weight, the reaction with the silylating agent used in the formation of a resist pattern, which will be described later, becomes difficult to proceed, and the resolution tends to decrease. On the other hand, when the proportion of m-cresol exceeds 90% by weight, the undercut of the obtained resist pattern tends to increase. The amount of formaldehyde used is 1 mole of mixed cresol,
It is preferably 0.6 to 2 mol, particularly preferably 0.6 to 1.
2 mol.

As the acid catalyst, hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid, etc. are used. The amount of the acid catalyst used is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ mol per mol of mixed cresol.

In the polycondensation, water is advantageously used as a reaction medium, but when the mixed cresol used is not dissolved in the aqueous formaldehyde solution and becomes a heterogeneous system from the initial stage of the reaction, a hydrophilic solvent is used as a reaction medium. It can also be used. Examples of the hydrophilic solvent used at this time include alcohols such as methanol, ethanol, propanol and butanol, and cyclic ethers such as tetrahydrofuran and dioxane.

The amount of these reaction media used is such that the reaction raw material 1
20 to 1000 parts by weight is preferable per 00 parts by weight.

The reaction temperature of the polycondensation can be appropriately adjusted depending on the reactivity of the reaction raw materials, but is preferably 10 to 10.
200 degreeC, More preferably, it is 70-150 degreeC. After completion of the polycondensation reaction, in order to remove the unreacted raw materials, the acid catalyst and the reaction medium existing in the system, the internal temperature is generally set to 130 to
The temperature is raised to 230 ° C., and the volatile matter is distilled off under reduced pressure. If necessary, the reaction system may be washed with water, and then the internal temperature may be raised as described above to distill off the volatile matter under reduced pressure.

The Mw of the novolak resin obtained as described above is 1,000 to 10,000, preferably 1,000 to 8,000, and particularly preferably 1.00.
It is 0 to 6,000. When Mw exceeds 10,000, undercutting occurs and the pattern shape deteriorates. The content of low molecular weight component having a polystyrene reduced molecular weight of less than 600 in the resin is 13% by weight or more, and preferably 15%.
It is at least wt%, particularly preferably 18 to 60 wt%.
If the content of the low molecular weight component is less than 13% by weight, the sensitivity is lowered and the exposure throughput is lowered.

1,2-condensed with the above novolak resin
Examples of the quinonediazide sulfonyl halide include 1,2-naphthoquinonediazide-4-sulfonyl chloride, 1,2-naphthoquinonediazide-5-sulfonyl chloride, 1,2-naphthoquinonediazide-6-sulfonyl chloride, 1,2-naphthoquinonediazide- 4-sulfonyl bromide, 1,2-naphthoquinonediazide-5-
Sulfonyl bromide, 1,2-naphthoquinonediazide-
1,2-naphthoquinone diazide sulfonyl halides such as 6-sulfonyl bromide; and 1,2-benzoquinone diazide-4-sulfonyl chloride, 1,2-benzoquinone diazide-5-sulfonyl chloride, 1,2-benzoquinone diazide-6-sulfonyl Chloride, 1,2-
Benzoquinonediazide-4-sulfonyl bromide, 1,
2-benzoquinonediazide-5-sulfonylbromide,
Mention may be made of 1,2-benzoquinonediazidesulfonyl halides such as 1,2-benzoquinonediazide-6-sulfonylbromide. Of these, 1,2-naphthoquinonediazide-4-sulfonyl chloride and 1,2
-Naphthoquinonediazide-5-sulfonyl chloride is preferred.

The condensation ratio between the novolak resin and the 1,2-quinonediazidesulfonyl halide is preferably 1 to 60 parts by weight of 1,2-quinonediazidesulfonyl group, more preferably 5 parts by weight per 100 parts by weight of the novolak resin.
˜50 parts by weight, particularly preferably 10 to 40 parts by weight. 1,2-quinonediazidesulfonyl group is 1
If the amount is less than parts by weight, the crosslinking reaction between the active species and the molecular chain of the novolak resin and between the active species and the 1,2-quinonediazidesulfonyl group due to thermal decomposition of the 1,2-quinonediazidesulfonyl group does not occur much. For this reason, the density of the non-radiation-exposed portion becomes small, so that the silylating agent used at the time of forming a resist pattern described later easily diffuses and reacts, and the radiation-irradiated portion and the non-irradiated portion are anisotropic. It is difficult to make a difference in the dry etching rate by the reactive oxygen plasma, and patterning tends to be difficult.

On the other hand, if the amount exceeds 60 parts by weight, most of the 1,2-quinonediazidosulfonyl group remains in its original form in a short-time irradiation, so that the amount of the 1,2-quinonediazidesulfonyl group is 1 during the heat treatment when absorbing and reacting the silylating agent. The thermal cross-linking reaction proceeds between the molecules of 2,2-quinonediazide sulfonate,
The subsequent silylating agent treatment tends to make it difficult for the silylating agent to be sufficiently absorbed. For this reason, the radiation-irradiated portion has insufficient dry etching resistance, and patterning tends to be difficult.

As the condensation solvent used in the condensation reaction, for example, acetone, dioxane, ethyl lactate, ethyl acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, methyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, acetonitrile, Methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone and the like can be mentioned. Usually, the total amount of novolak resin and 1,2-quinonediazidesulfonyl halide is 10
100 to 10,000 parts by weight, preferably 200 to 3,000 parts by weight, are used per 0 parts by weight. In addition, in the condensation reaction, water may be added, if necessary, in order to dissolve the generated salt of the base and the halogen in the solvent. The amount of water added is 1 to 10 parts by weight with respect to 100 parts by weight of the condensation solvent.

As the basic catalyst used in the condensation reaction, sodium hydrogen carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate,
Alkali metal salts such as potassium hydrogen carbonate and potassium carbonate;
Examples thereof include amines such as triethylamine, triethanolamine, tributylamine, monoethanolamine and pyridine; ammonium salts such as ammonium hydroxide and trimethylammonium, and ammonia. The number of moles of 1,2-quinonediazidesulfonyl halide is 0. It is preferable to use 0.1 to 10 times, 0.5 to
A 2.0-fold molar number is more preferably used. The condensation reaction is preferably 5 to 50 ° C., more preferably 10 to 40.
It is carried out at a temperature of ° C. The reaction time is preferably 15 minutes to 10 hours, more preferably about 30 minutes to 5 hours.

The composition used in the present invention contains an organic acid in order to facilitate the reaction of the irradiated portion with the silylating agent.
An organic acid salt, an organic acid halogenide, or a substance that generates an acid upon irradiation with radiation (hereinafter, referred to as “acid generator”) can be included.

Here, as the organic acid, for example, aromatic sulfonic acid or aromatic carboxylic acid can be preferably mentioned. Preferred are naphthalenesulfonic acid, naphthalenecarboxylic acid, diazoquinonesulfonic acid and diazoquinonecarboxylic acid. Examples of these include 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, 1,2-naphthoquinonediazide-4-sulfonic acid, 1,2-naphthoquinonediazide-5-sulfonic acid,
1,2-naphthoquinonediazide-6-sulfonic acid, 1,2
-Naphthoquinonediazide-7-sulfonic acid, 1,2-naphthoquinonediazide-8-sulfonic acid, 2,1-naphthoquinonediazide-4-sulfonic acid, 2,1-naphthoquinonediazide-5-sulfonic acid, 2,1-naphtho Quinonediazide-6-sulfonic acid, 2,1-naphthoquinonediazide-7-sulfonic acid, 2,1-naphthoquinonediazide-
8-sulfonic acid, 1,2-benzoquinonediazide-3-
Sulfonic acid, 1,2-benzoquinonediazide-4-sulfonic acid, 1,2-benzoquinonediazide-5-sulfonic acid, 1,2-benzoquinonediazide-6-sulfonic acid,
1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, 1,2-naphthoquinonediazide-4-carboxylic acid,
1,2-naphthoquinonediazide-5-carboxylic acid, 1,2
-Naphthoquinonediazide-6-carboxylic acid, 1,2-naphthoquinonediazide-7-carboxylic acid, 1,2-naphthoquinonediazide-8-carboxylic acid, 2,1-naphthoquinonediazide-4-carboxylic acid, 2,1-naphtho Quinonediazide-5-carboxylic acid, 2,1-naphthoquinonediazide-6-carboxylic acid, 2,1-naphthoquinonediazide
7-carboxylic acid, 2,1-naphthoquinonediazide-8-
Carboxylic acid, 1,2-benzoquinonediazide-3-carboxylic acid, 1,2-benzoquinonediazide-4-carboxylic acid, 1,2-benzoquinonediazide-5-carboxylic acid and 1,2-benzoquinonediazide-6-carboxylic acid Can be mentioned.

Examples of the organic acid salts and organic acid halogenides include ammonium salts, amine salts of the above organic acids and acid halogenides corresponding to these acids. Of these, particularly preferred is the following formula (1)
The diazoquinone compound represented by is used.

[0029]

[Chemical 1]

Acid generating substances include ultraviolet rays, deep ultraviolet rays, X-rays,
It is a substance that generates an acid when irradiated with radiation such as an electron beam and visible light. Here, the generated acid is, for example, an inorganic acid such as sulfonic acid, phosphoric acid, iodic acid, diazo acid, hydrogen halide; or nitrobenzyl sulfonic acid, cyanobenzyl sulfonic acid, nitrobenzyl carboxylic acid, cyanobenzyl carboxylic acid, Organic acids such as nitrobenzyl phosphoric acid, cyanobenzyl phosphoric acid, nitrobenzyl nitric acid and cyanobenzyl nitric acid.

Examples of such an acid generator include onium salts such as sulfonium, phosphonium, iodonium and diazonium; nitrobenzyl halides; halogenated hydrocarbons; phenyl nitrobenzyl sulfonate, naphthyl nitrobenzyl sulfonate, o-nitrobenzyl. −
9,10-diethoxyanthracene-2-sulfonate, p-nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate, o-nitrobenzyl-9,
10-dimethoxyanthracene-2-sulfonate, p
-Nitrobenzyl-9,10-dimethoxyanthracene-2-sulfonate, o-nitrobenzyl-9,10-
Dipropoxyanthracene-2-sulfonate, p-nitrobenzyl-9,10-dipropoxyanthracene-
Nitrobenzyl sulfonates such as 2-sulfonates; Benzoin sulfonates such as benzoin tosylate and 2-methylbenzointosylate; Cyanobenzyl sulfonates such as phenyl cyanobenzyl sulfonate and naphthobenzyl naphthol; Nitrobenzyl carboxylic acid Acid phenyl, nitrobenzylcarboxylic acid naphthol and other nitrobenzylcarboxylic acid esters;

Phenyl cyanobenzyl carboxylic acid, cyanobenzyl carboxylic acid naphthol and other cyanobenzyl carboxylic acid esters; nitrobenzyl phosphoric acid phenyl, nitrobenzyl phosphoric acid naphthol and other nitrobenzyl phosphoric acid esters; cyanobenzyl phosphoric acid phenyl, cyanobenzyl phosphorus Examples thereof include cyanobenzyl phosphate such as acid naphthol; nitrobenzyl nitrate such as phenyl nitrobenzyl nitrate and naphthyl nitrate naphthol; cyanobenzyl nitrate such as phenyl cyanobenzyl nitrate and naphthonitrile nitrate.

These organic acids, organic acid salts, organic acid halogenides and acid generators are added to 100 parts by weight of 1,2-quinonediazide sulfonic acid ester of novolak resin.
Preferably 0.1 to 20 parts by weight, particularly preferably 0.5 to
It is used in a proportion of 10 parts by weight.

The composition of the present invention may contain a surfactant or the like in order to improve coating properties such as striation after the formation of a dry coating film. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, polyethylene glycol dilaurate, polyethylene glycol distearate, Ftop EF301. ,
EF303, EF352 (manufactured by Shin-Akita Kasei Co., Ltd.), Megafac F171, F172, F173 (manufactured by Dainippon Ink Co., Ltd.), Asahi Gart AG710 (Asahi Glass Co., Ltd.)
Manufactured by Sumitomo 3M Co., Ltd., Surflon S-382, SC10
1, SC102, SC103, SC104, SC10
5, SC106 (manufactured by Asahi Glass Co., Ltd.), organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), acrylic acid-based or methacrylic acid-based (co) polymer polyflow No. 75, No. 90, No. 95, WS (manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd.) and the like can be mentioned. The content of these surfactants is preferably 2 parts by weight or less, more preferably 0.005 to 1 part by weight per 100 parts by weight of the 1,2-quinonediazide sulfonic acid ester of the novolak resin.
Parts by weight.

The composition used in the present invention may further contain a dye, a pigment, an ultraviolet absorber, etc. in order to visualize the latent image in the radiation irradiated area and to reduce the effect of halation during radiation irradiation. it can. Preferred dyes or pigments are, for example, Neopengelb 075 (manufactured by Basuf), Neozapongelb 073 (same), Solvent Yellow 162, SOT Yellow 3 (Hodogaya Chemical Co., Ltd.).
Manufactured by Mitsubishi Chemical Co., Ltd.), Macrolex Yellow (manufactured by Bayer), and hydroxyazobenzene.

Further, a preferable ultraviolet absorber is, for example, 2- (2'-hydroxy-5'-methylphenyl).
-Benzotriazole, 2- (2'-hydroxy-5 '
-T-butylphenyl) -benzotriazole, 2-
(2'-Hydroxy-3 ', 5'-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-
Hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl) -benzotriazole, 2- ( 2'-hydroxy-3 ',
5'-di-t-butylphenyl) -benzotriazole, 2- (2'-hydroxy-5'-t-butylphenyl) -benzotriazole, 2- (2'-hydroxy-
5'-t-octylphenyl) -benzotriazole and the like can be mentioned. Furthermore, the composition used in the present invention may contain a storage stabilizer, an antifoaming agent, etc., if necessary.

The composition used in the present invention is prepared to have a solid content concentration of 5 to 50% by weight by dissolving the 1,2-quinonediazide sulfonic acid ester of the above novolak resin and the above-mentioned various additives in an organic solvent. For example, it is filtered with a filter having a pore size of about 0.2 μm.

Examples of the organic solvent used here include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, propylene glycol methyl ether acetate, and methyl cellosolve acetate. , Ethyl cellosolve acetate, butyl cellosolve acetate, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, acetonylacetone, acetophenone,
Isophorone, benzyl ethyl ether, 1,2-dibutoxyethane, dihexyl ether, caproic acid, caprylic acid, 1-octanol, 1-nonanol, 1-decanol, benzyl alcohol, ethyl acetate, butyl acetate,
Isoamyl acetate, 2-ethylhexyl acetate, benzyl acetate, benzyl benzoate, diethyl oxalate, dibutyl oxalate, diethyl malonate, ethyl lactate, methyl lactate, propyl lactate, butyl lactate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate , Dimethyl maleate, diethyl maleate, dibutyl maleate, dibutyl phthalate, dimethyl phthalate, ethylene carbonate, propylene carbonate, γ-butyrolactone, and dimethylimidazolidinone. The composition thus prepared can be applied to a silicon wafer or the like by spin coating, flow coating, roll coating or the like.

The composition applied on the substrate is prebaked at a temperature of, for example, 70 to 130 ° C. in order to remove the solvent. Then, the resist layer on the substrate is irradiated with radiation, for example, only ultraviolet rays, far ultraviolet rays, X-rays, electron beams, visible light, etc., in a portion selected through a pattern.

By the irradiation of radiation, the 1,2-quinonediazidesulfonyl group of the 1,2-quinonediazide sulfonic acid ester of the novolak resin is decomposed in the irradiation portion, and an acid is generated when an acid-generating substance is contained. .. Then, the substrate is heat-treated if necessary. The heat treatment at this time is preferably performed at a temperature of 120 to 200 ° C. By this heat treatment, the 1,2-quinonediazidesulfonyl group existing in the unirradiated portion reacts with the novolac resin and the 1,2-quinonediazidesulfonyl group to form a crosslinked structure in the molecular chain. On the other hand, since most of the 1,2-quinonediazidesulfonyl group has already been decomposed in the radiation-exposed portion, the formation of a crosslinked structure is extremely small compared to the non-radiation-exposed portion.

Next, by treatment with a silylating agent, the radiation-exposed portion absorbs the silylating agent and reacts, but the non-radiation-exposed portion absorbs the silylating agent and reacts because of the crosslinked structure. A negative latent image that is strongly suppressed and is resistant to dry etching is formed.

Examples of useful silylating agents include, for example, tetrachlorosilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylbromosilane, trimethyliodosilane, triphenylchlorosilane, hexamethyldisilazane, 1,1,3,3. -Tetramethyldisilazane, heptamethyldisilazane, hexaphenyldisilazane, 1,3-bis (chloromethyl)
-1,1,3,3-Tetramethyldisilazane, N-trimethylsilylimidazole, N-trimethylsilylacetamide, N-trimethylsilyldimethylamine, N-trimethylsilyldiethylamine, hexamethylsilanediamine, N, O-bis (triethylsilyl) acetimide , N, N'-bis (trimethylsilyl) urea, N, N '
-Diphenyl-N- (trimethylsilyl) urea and the like can be mentioned. The treatment temperature of the radiation-sensitive resin layer with the silylating agent is determined by the composition of the radiation-sensitive resin layer, the type of the silylating agent used and the treatment time, and is preferably selected from 0 to 250 ° C. It is possible, and it is more preferably 140 to 200 ° C.

After the treatment with the silylating agent as described above, a desired negative pattern is obtained by dry development, for example, anisotropic oxygen plasma etching.

[0044]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples, various characteristics were evaluated as follows.

Polystyrene-equivalent molecular weight: The polystyrene-equivalent molecular weight was determined by gel permeation chromatography (GPC). High-speed GPC device HL manufactured by Tosoh Corporation
C-802A, detector is RI, column is Tosoh Corp. TSK-GEL G4000H8, G3000
H8, G2000H8 × 2, the elution solvent was THF, the flow rate was 1.2 ml / min, the column temperature was 40 ° C., and the sample concentration was 0.02 g / 10 ml (THF).

The weight% of the low-molecular-weight component corresponding to a polystyrene-equivalent molecular weight of 600 or less has an area of the obtained chromatogram of S ₁ , and a polystyrene-equivalent molecular weight of 60.
It is a value obtained from the following equation, where S ₂ is the area of 0 or less. W = (S ₂ / S ₁ ) × 100

Undercut: The cross section of the resist pattern was observed with a scanning electron microscope. The degree of undercut can be expressed by the dimensional ratio b / a of a and b shown in FIGS. Here, a is the dimension of the thickest part above the resist pattern, and b is the dimension of the thinnest part due to undercut. The measurement was performed with a line-and-space pattern having a design of 0.6 μm.

Optimal exposure dose: In a pattern having a mask size of 0.6 μm, the exposure dose at which the size of FIG.

Example 1 (1) 303 g of m-cresol and 130 g of p-cresol were placed in a flask equipped with a stirrer, a condenser and a thermometer.
276 g of 37% by weight formaldehyde aqueous solution and 0.756 g of oxalic acid dihydrate were charged. While stirring
The flask was immersed in an oil bath and allowed to react for 1 hour while maintaining the internal temperature at 100 ° C. Thereafter, 500 g of water was added and stirred, and the mixture was left standing for 2 minutes, and the treatment of removing water, unreacted monomer, unreacted formaldehyde and oxalic acid in the upper layer was repeated twice. After further raising the oil bath temperature to 180 ° C. and stirring for 2 hours, the pressure inside the flask was reduced to remove residual water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 1600, and the low molecular weight component was 36% by weight.

(2) Novolak resin 1 obtained in (1)
After dissolving 00 g, 1,2-naphthoquinonediazide-5-sulfonyl chloride 36.4 g and water 77.6 g in 2300 g propylene glycol monomethyl ether acetate (hereinafter referred to as "PGMA"), 8 wt%
188.6 g of a PGMA solution of triethylamine in 1 was added, and the mixture was stirred and reacted for 90 minutes. Thereafter, 14.92 ml of 1N hydrochloric acid was added, and the mixture was stirred for 20 minutes, then 1 l of water was added and stirred, and then allowed to stand still to separate an aqueous layer and an organic layer. After discarding the aqueous layer, the same water washing operation was performed twice more to remove the triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Then, PGMA and water were removed from the reaction solution under reduced pressure to obtain 128 g of a partially esterified novolak resin (hereinafter referred to as "esterified novolak resin").

(3) 20 g of the esterified novolak resin obtained in (2) was dissolved in 50 g of PGMA. Then 1,2-naphthoquinonediazide-5-sulfonic acid 0.2 g
Was dissolved in 0.8 g of 1,3-dimethyl-2-imidazolidone, and this solution was gradually added to the esterified novolak resin solution with stirring and stirred until a uniform solution was obtained. Next, surfactant Megafac F172 (Dainippon Ink and Co., Ltd.)
0.2 g of a 2% by weight PGMA solution prepared in (Production) was added and stirred.
Then, the solution of the composition was prepared by filtering with a membrane filter having a pore size of 0.2 μm.

(4) The solution obtained in (3) was applied onto a silicon wafer with a spinner and then prebaked at 120 ° C. for 90 seconds on a hot plate to form a resist film having a thickness of 1.5 μm. Next, this was exposed through a pattern mask using a stepper NSR1755G7A manufactured by Nikon Corporation. Then expose the exposed silicon wafer to 1
The substrate was baked in vacuum at 70 ° C. for 3 minutes (referred to as “pre-silylation bake”), and the substrate was treated with hexamethyldisilazane vapor for 4 minutes while baking at 170 ° C.

A magnetron-enhanced reactive ion etching system (MARC Inc. ARIES
-C), and dry development was performed by anisotropic oxygen plasma etching to form a resist pattern. The etching conditions at this time are as follows. RF power: 1000 W, oxygen flow rate: 70 SCCM, pressure: 4 mtorr, etching time: 2 minutes 30 seconds,

(5) When the pattern profile after dry development was observed, a good pattern with almost no undercut was obtained with b / a = 0.99. The optimum exposure amount was 150 mJ / cm ² .

Comparative Example 1 (1) 120 g of pt-butylphenol, 300 g of phenol, 86 g of paraformaldebito, 105 g of 37% by weight formaldehyde aqueous solution and 105 g of oxalic acid dihydrate were placed in the same flask as in Example 1 (1). 5g was charged. While stirring, soak the flask in an oil bath and adjust the internal temperature to 10
The reaction was carried out for 3 hours while maintaining the temperature at 0 ° C. After that, the oil bath temperature was raised to 190 ° C, and the pressure inside the flask was reduced at the same time.
Water, unreacted phenols, formaldehyde and oxalic acid were removed. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin is 1
4,200 and the low molecular weight component was 13.9% by weight.

(2) Novolak resin 2 obtained in (1)
5 g, 1,2-naphthoquinonediazide-5-sulfonyl chloride 9.1 g and water 33 g 660 g PGMA
8% by weight of triethylamine PGMA after dissolution in
A solution (47.15 g) was added and the mixture was stirred and reacted for 90 minutes. After that, 3.73 ml of 1N hydrochloric acid was added and stirred for 20 minutes,
Next, 250 ml of water was added and the mixture was stirred and then left to stand to separate an aqueous layer and an organic layer. After discarding the aqueous layer, the same water washing operation was performed twice more to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Then, PGMA and water were removed from the reaction solution under reduced pressure to obtain 32 g of esterified novolac resin.

(3) A solution of the composition was prepared in the same manner as in Example 1 (3) using the esterified novolac resin obtained in (2). (4) A resist pattern was formed in the same manner as in Example 1 (4). (5) When the pattern profile after dry development was observed, it was found that the undercut was large with b / a = 0.80. The optimum exposure amount was 140 mJ / cm ² .

Example 2 (1) In the same flask as in Example 1 (1), 389 g of m-cresol, 43 g of p-cresol, 308 g of a 37% by weight aqueous formaldehyde solution and oxalic acid dihydrate.
756 g was charged. The flask was immersed in an oil bath with stirring, and the reaction was carried out for 2 hours while maintaining the internal temperature at 110 ° C. Thereafter, the oil bath temperature was raised to 180 ° C., and at the same time, the pressure inside the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 3800, and the low molecular weight component was 22.
% By weight.

(2) Using the novolak resin obtained in (1), 120 g of an esterified novolak resin was obtained in the same manner as in Example 1 (2). (3) A solution of the composition was prepared in the same manner as in Example 1 (3) using the esterified novolak resin obtained in (2).

(4) Using the solution obtained in (3), a resist pattern was formed in the same manner as in Example 1 (4). (5) When the pattern after dry development was observed, b /
The optimum exposure amount was 400 mJ / cm ² at a = 0.96.

Example 3 (1) 216 g of m-cresol, 216 g of p-cresol, 276 g of 37% by weight aqueous formaldehyde solution and 0.252 g of oxalic acid dihydrate were charged in the same flask as in Example 1 (1). The flask was immersed in an oil bath with stirring, and the reaction was carried out for 2 hours while maintaining the internal temperature at 110 ° C. Thereafter, 600 g of water was added, and the mixture was stirred and allowed to stand for 3 minutes, and then the suspension of water, unreacted cresol, formaldehyde and oxalic acid in the upper layer was removed. In addition, set the oil bath temperature to 18
Water, unreacted cresol, formaldehyde and oxalic acid were removed by raising the temperature to 0 ° C. and simultaneously reducing the pressure in the flask. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 2100, and the low molecular weight component was 31% by weight.

(2) Using the novolak resin obtained in (1), 125 g of an esterified novolak resin was obtained in the same manner as in Example 1 (2). (3) A solution of the composition was prepared in the same manner as in Example 1 (3) using the esterified novolak resin obtained in (2). (4) Using the solution obtained in (3), a resist pattern was formed in the same manner as in Example 1 (4). (5) When the pattern after dry development was observed, b /
The optimum exposure amount was 180 mJ / cm ² at a = 0.97.

Example 4 (1) 130 g of m-cresol, 303 g of p-cresol, 260 g of 37% by weight aqueous formaldehyde solution and 0.756 g of oxalic acid dihydrate were charged in the same flask as in Example 1 (1). The flask was immersed in an oil bath with stirring, and the reaction was carried out for 2 hours while maintaining the internal temperature at 100 ° C. Thereafter, 500 g of water was added, and the mixture was stirred and allowed to stand for 2 minutes, and then the operation of removing the upper layer water, unreacted cresol, formaldehyde and oxalic acid suspension was performed twice.
The oil bath temperature was further raised to 200 ° C., and after stirring for 2 hours, the pressure inside the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 2500, and the low molecular weight component was 30.
% By weight.

(2) Using the novolak resin obtained in (1), 125 g of an esterified novolak resin was obtained in the same manner as in Example 1 (2). (3) A solution of the composition was prepared in the same manner as in Example 1 (3) using the esterified novolak resin obtained in (2).

(4) Using the solution obtained in (3), a resist pattern was formed in the same manner as in Example 1 (4). (5) When the pattern after dry development was observed, b /
a = 0.98, and the optimum exposure amount was 300 mJ / cm ² . It was.

Example 5 25 g of the novolac resin obtained in Example 1 (1) and 1,
2-naphthoquinonediazide-5-sulfonyl chloride 1
After dissolving 0.6 g and 35 g of water in 700 g of PGMA, a solution of 8% by weight of triethylamine in PGMA 5
4.9 g was added and stirred and reacted for 90 minutes. Then 1
Add 4.34 ml of normal hydrochloric acid and stir for 20 minutes, then
After adding 250 ml of water and stirring, the mixture was allowed to stand and the aqueous layer and the organic layer were separated. After discarding the water layer, perform the same water washing procedure as above.
This was repeated, and the triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution were removed. PGMA and water were removed from the reaction solution thus washed with water under reduced pressure to obtain 33 g of an esterified novolak resin.

A solution of the composition was prepared in the same manner as in Example 1 (3) using the above esterified novolak resin.
Then, a resist pattern was formed in the same manner as in Example 1 (4). Observation of the pattern after dry development revealed that
/A=0.99 and the optimum exposure amount was 200 mJ / cm ² .

Example 6 25 g of the novolac resin obtained in Example 1 (1) and 1,
After dissolving 7.5 g of 2-naphthoquinonediazide-5-sulfonyl chloride and 20 g of water in 320 g of PGMA, 8% by weight of a PGMA solution of triethylamine 3
8.8 g was added and stirred and reacted for 90 minutes. Then 1
Add 3.07 ml of normal hydrochloric acid, stir for 20 minutes, then PG
After 250 ml of a saturated MA aqueous solution was added and stirred, the mixture was allowed to stand and the aqueous layer and the organic layer were separated. The aqueous layer was discarded, and the same water washing operation was performed twice more to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. PGMA and water were removed from the reaction solution washed with water in this manner under reduced pressure to obtain 31 g of an esterified novolak resin.

Using the above esterified novolak resin,
A solution of the composition was prepared in the same manner as in Example 1 (3). Then, a resist pattern was formed in the same manner as in Example 1 (4). Observation of the pattern after dry development revealed that b / a
== 0.99, the optimum exposure amount was 100 mJ / cm ² .

Example 7 (1) 20 g of the esterified novolak resin obtained in Example 1 (2) and 0.6 g of p-nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate were treated with PGMA.
After dissolving in 60 g, 0.2 g of a 10 wt% PGMA solution of Polyflow No. 90 manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd. was added and stirred. Then, the solution of the composition was prepared by filtering with a membrane filter having a pore size of 0.2 μm.

Then, a resist pattern was formed in the same manner as in Example 1 (4) except that the pre-silylation baking and the silylation treatment were carried out at 160 ° C. When the pattern after dry development was observed, b / a = 0.95 and the optimum exposure amount was 220 mJ / cm ² .

Example 8 (1) 20 g of the esterified novolak resin obtained in Example 1 (2) and 0.6 g of Neo Pengelp 075 (manufactured by BASF) as a dye were dissolved in 60 g of PGMA. Then 1,
0.2 g of 2-naphthoquinonediazide-5-sulfonic acid was dissolved in 0.8 g of 1,3-dimethyl-2-imidazolidone and gradually added to the resin solution while stirring, and stirred until a uniform solution was obtained. Then, the solution was filtered through a membrane filter having a pore size of 0.2 μm to prepare a resist composition solution.

Then, a resist pattern was formed in the same manner as in Example 1 (4). When the pattern after dry development was observed, b / a = 0.99 and the optimum exposure amount was 140 mJ /
It was cm ² .

Example 9 (1) The same flask as in Example 1 (1) was charged with 303 g of m-cresol, 130 g of p-cresol, 308 g of 37% by weight aqueous formaldehyde solution and 0.756 g of oxalic acid dihydrate. The flask was immersed in an oil bath with stirring, and the reaction was carried out for 2 hours while maintaining the internal temperature at 100 ° C. Thereafter, the oil bath temperature was raised to 180 ° C., and at the same time, the pressure inside the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolac resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 5600, and the low molecular weight component was 2
It was 0% by weight.

(2) Novolak resin 1 obtained in (1)
00 g, 1,2-naphthoquinonediazide-5-sulfonyl chloride 25.3 g and water 15 g 2200 g P
After dissolving in GMA, 8% by weight of triethylamine P
131 g of GMA solution was added and stirred and reacted for 90 minutes. Then, 1N hydrochloric acid (10.4 ml) was added, the mixture was stirred for 20 minutes, then 1 liter of water was added and the mixture was stirred and allowed to stand to separate an aqueous layer and an organic layer. Discard the aqueous layer and perform the same water washing operation for 2 more times.
This was repeated, and the triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution were removed. Then, PGMA and water were removed from the reaction solution under reduced pressure to obtain 118 g of esterified novolak resin.

(3) 20 g of the esterified novolak resin obtained in (2) was dissolved in 55 g of PGMA. Then
1,2-naphthoquinonediazide-5-sulfonic acid 0.2 g
Was dissolved in 0.8 g of 1,3-dimethyl-2-imidazolidone, and this solution was gradually added to the esterified novolak resin solution with stirring and stirred until a uniform solution was obtained. Next, surfactant Megafac F172 (Dainippon Ink and Co., Ltd.)
0.2 g of a 2% by weight PGMA solution of (produced by K.K.) was added and stirred.
Then, it was filtered through a membrane filter having a pore size of 0.2 μm to prepare a composition solution.

(4) Using the solution obtained in (3), a resist pattern was formed in the same manner as in Example 1 (4). (5) When the pattern after dry development was observed, b /
When a = 0.92, the optimum exposure amount was 450 mJ / cm ² .

Comparative Example 2 (1) The same flask as in Example 1 (1) was charged with 303 g of m-cresol, 130 g of p-cresol, 308 g of a 37% by weight aqueous formaldehyde solution and 0.756 g of oxalic acid dihydrate. While stirring, the flask was immersed in an oil bath and allowed to react for 3 hours while maintaining the internal temperature at 110 ° C. Then, the temperature of the oil bath was raised to 180 ° C. and the pressure in the flask was reduced to 10 mmHg to remove water, unreacted cresol, formaldehyde and oxalic acid. Then, the molten novolak resin was returned to room temperature and recovered. The Mw of the obtained novolak resin was 15,300, and the low molecular weight component was 11% by weight.

(2) Novolak resin 1 obtained in (1)
00 g, 1,2-naphthoquinonediazide-5-sulfonyl chloride (20.3 g) and water (112 g) were dissolved in 2140 g of PGMA, and 8% by weight of a triethylamine PGMA solution (105 g) was added and stirred to react for 90 minutes. Then, 8.3 ml of 1N hydrochloric acid was added, and the mixture was stirred for 20 minutes, then 1 l of water was added and stirred, and the mixture was allowed to stand and separated into an aqueous layer and an organic layer. After discarding the aqueous layer, the same water washing operation was performed twice more to remove the triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Then, PGMA and water were removed from the reaction solution under reduced pressure to obtain 115 g of esterified novolak resin.

(3) 20 g of the esterified novolak resin obtained in (2) was dissolved in 60 g of PGMA. Then
1,2-naphthoquinonediazide-5-sulfonic acid 0.2 g
Was dissolved in 0.8 g of 1,3-dimethyl-2-imidazolidone, and this solution was gradually added to the esterified novolak resin solution with stirring and stirred until a uniform solution was obtained. Next, surfactant Megafac F172 (Dainippon Ink and Co., Ltd.)
0.2 g of a 2% by weight PGMA solution of (produced by K.K.) was added and stirred.
Then, the mixture was filtered through a membrane filter having a pore size of 0.2 μm to prepare a solution of the composition.

(4) Using the solution obtained in (3), an attempt was made to obtain a resist pattern on a silicon wafer in the same manner as in Example 1 (4). The film was completely etched and no pattern was obtained.

The evaluation results of Examples 1 to 9 and Comparative Examples 1 and 2 are summarized in Table 1 together with the 1,2-quinonediazide sulfonic acid ester of the novolak resin.

[0083]

[Table 1]

[0084]

According to the pattern forming method of the present invention, it is possible to provide a resist pattern forming method which is excellent in the pattern shape and throughput in which undercut does not occur.

[Brief description of drawings]

FIG. 1 shows one of pattern cross-sectional shapes having an undercut.

FIG. 2 shows another pattern cross-sectional shape having an undercut.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 7352-4M H01L 21/30 361 K

Claims (1)

Claims (1). (1). Obtained by polycondensing mixed cresol containing m-cresol and p-cresol and formaldehyde, and having a polystyrene reduced weight average molecular weight of 1,000 to 10. A radiation-sensitive resin composition containing a 1,2-quinonediazide sulfonic acid ester of a novolac resin containing 13% by weight or more of a low molecular weight component having a polystyrene-converted molecular weight of less than 600 is applied in layers. ). Irradiate only selected parts,
(3). Treatment with a silylating agent vapor to selectively absorb the silylating agent in the irradiation section to cause reaction, and (4).
A method for forming a resist pattern, characterized in that the layer is dry-developed by anisotropic oxygen plasma etching to selectively remove the non-radiation-irradiated portion of the layer.