JP2943138B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 process of manufacturing semiconductor devices such as ICs and LSIs, a quinonediazide compound is mixed with a negative photoresist in which cyclized polyisoprene is mixed with bisazide on a substrate to be processed or a novolak resin. Apply a radiation-sensitive resin composition such as a positive photoresist,
Mercury lamp g-line (wavelength 436mn) and i-line (365nm)
A photolithography method is employed in which a pattern is formed by exposing to light using a developer and developing with a developer.

However, in recent years, LSIs have been further miniaturized,
The minimum dimension of a pattern to be formed on a substrate is entering an area of 1 μm or less, and in such an area, even if a conventional photolithography method using a developing solution for development is used, a step structure is particularly exhibited. When a substrate is used, there arises a problem that a sufficient resolution cannot be obtained due to the influence of light reflection at the time of exposure and a problem such as a shallow depth of focus in an exposure system.

As a method for solving such a problem, a resist pattern is formed by performing dry development by etching using gas plasma such as anisotropic oxygen plasma instead of developing using a developer in photolithography. There are known ways to do this.

JP-A-61-107346 discloses a method in which a photosensitive resin layer containing a polymer mixed or bonded with a photoactive compound is applied to a substrate, and the layer is exposed at the irradiated portion of the layer. When exposed to light or ultraviolet light, the silylating agent has a property capable of selectively diffusing into the irradiated portion; exposing the photosensitive resin layer to only a selected portion of the layer. Exposure to ultraviolet or visible light through a mask that causes

[0006] The photosensitive resin layer is treated with a silylating agent, whereby the silylating agent is selectively absorbed by the irradiated portion of the coating (photosensitive resin layer) so that the irradiated portion is exposed to light. React with the part

A method is described in which a photosensitive resin layer thus treated is dry-developed by plasma etching to selectively remove a non-irradiated portion to obtain a desired negative figure.

According to this method, since the silylating agent absorbed in the portion irradiated with ultraviolet light or visible light has extremely high resistance to oxygen plasma, the etching is sharply performed by etching with oxygen plasma having high anisotropy. It is known that a resist pattern having an appropriate side wall can be obtained, and thus a fine pattern can be resolved.

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

[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 method of forming a resist pattern which does not cause undercut and has excellent pattern shape and throughput. Still other 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 as follows: (1) Obtained by polycondensing mixed cresol containing m-cresol and p-cresol with formaldehyde. Weight average molecular weight in terms of polystyrene (hereinafter referred to as “Mw”).
) Having a molecular weight of 1,000 to 10,000 and a polystyrene-equivalent molecular weight of less than 600
A radiation-sensitive resin composition containing 1,2-quinonediazidesulfonic acid ester of a novolak resin containing at least

(2) irradiating only the selected portion with radiation; (3) treating with a silylating agent vapor to cause the silylating agent to be selectively absorbed in the irradiated portion and reacted; The method is characterized in that the layer is dry-developed by anisotropic oxygen plasma etching to selectively remove non-irradiated portions of the layer.

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

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

Here, the proportion of m-cresol in the mixed cresol is preferably from 40 to 90% by weight, more preferably from 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 a silylating agent used at the time of forming a resist pattern described later hardly progresses, and the resolution tends to decrease. On the other hand, when the proportion of m-cresol exceeds 90% by weight, the resulting resist pattern tends to have a large undercut. The amount of formaldehyde used per mole of mixed cresol
Preferably from 0.6 to 2 mol, particularly preferably from 0.6 to 1.
2 moles.

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

In the polycondensation, water is advantageously used as a reaction medium. However, when the mixed cresol used does not dissolve in an aqueous formaldehyde solution and becomes a heterogeneous system from the beginning of the reaction, a hydrophilic solvent is used as the reaction medium. 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
20 to 1000 parts by weight per 00 parts by weight is preferred.

The reaction temperature of the polycondensation can be appropriately adjusted according to the reactivity of the reaction raw materials, but is preferably from 10 to 10.
The temperature is 200 ° C, more preferably 70 to 150 ° C. After the completion of the polycondensation reaction, in order to remove unreacted raw materials, acid catalyst and reaction medium present in the system, the internal temperature is generally raised to 130 to
The temperature is raised to 230 ° C. and the volatile components are distilled off under reduced pressure. If necessary, after washing the reaction system with water, the internal temperature can be increased as described above, and volatile components can be distilled off 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 1,000.
0 to 6,000. If Mw exceeds 10,000, an undercut occurs and the pattern shape deteriorates. Further, the content of the low molecular weight component having a polystyrene reduced molecular weight of less than 600 in the resin is 13% by weight or more, preferably 15% by weight or more.
% By weight or more, particularly preferably 18 to 60% by weight.
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, and 1,2-naphthoquinonediazide-chloride. 4-sulfonyl bromide, 1,2-naphthoquinonediazide-5
Sulfonyl bromide, 1,2-naphthoquinonediazide-
1,2-naphthoquinonediazide sulfonyl halide such as 6-sulfonyl bromide; and 1,2-benzoquinonediazide-4-sulfonyl chloride, 1,2-benzoquinonediazide-5-sulfonyl chloride, 1,2-benzoquinonediazide-6-sulfonyl Chloride, 1,2-
Benzoquinonediazide-4-sulfonyl bromide, 1,
2-benzoquinonediazide-5-sulfonyl bromide,
Examples thereof include 1,2-benzoquinonediazide-6-sulfonyl bromide and other 1,2-benzoquinonediazidosulfonyl halides. Of these, 1,2-naphthoquinonediazide-4-sulfonyl chloride and 1,2
-Naphthoquinonediazide-5-sulfonyl chloride is preferred.

The condensation rate of the novolak resin with 1,2-quinonediazidosulfonyl halide is preferably 1 to 60 parts by weight, more preferably 5 to 1,2 parts by weight, per 100 parts by weight of the novolak resin.
The proportion is preferably from 50 to 50 parts by weight, particularly preferably from 10 to 40 parts by weight. 1,2-quinonediazidosulfonyl group is 1
If the amount is less than 1 part by weight, the crosslinking reaction between the active species and the molecular chain of the novolak resin due to the thermal decomposition of the 1,2-quinonediazidosulfonyl group and between the active species and the 1,2-quinonediazidosulfonyl group do not occur much. For this reason, the density of the non-irradiated portion is reduced, and the silylating agent used in forming a resist pattern described later easily diffuses and reacts, so that the anisotropic portion is irradiated between the irradiated portion and the non-irradiated portion. 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 the form as it is when irradiated with radiation for a short period of time. Thermal crosslinking reaction proceeds between the molecules of 2,2-quinonediazidesulfonic acid ester,
There is a tendency that the silylating agent is not sufficiently absorbed in the subsequent silylating agent treatment. For this reason, there is a tendency that patterning becomes difficult due to insufficient dry etching resistance of the irradiated portion.

Examples of the condensation solvent used in the condensation reaction include acetone, dioxane, ethyl lactate, ethyl acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, methyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, acetonitrile, and the like. Examples thereof include methyl ethyl ketone, diisobutyl ketone, and methyl isobutyl ketone. Usually, the total amount of novolak resin and 1,2-quinonediazidosulfonyl halide is 10%.
It is used in an amount of 100 to 10,000 parts by weight, preferably 200 to 3,000 parts by weight, per 0 parts by weight. In addition, at the time of the condensation reaction, water can be added as necessary to dissolve the salt of the generated base and halogen in the solvent. The amount of water to be added is 1 to 10 parts by weight based on 100 parts by weight of the condensation solvent.

The basic catalyst used in the condensation reaction includes sodium bicarbonate, sodium carbonate, sodium hydroxide, potassium hydroxide, sodium bicarbonate,
Alkali metal salts such as potassium hydrogen carbonate and potassium carbonate;
Amines such as triethylamine, triethanolamine, tributylamine, monoethanolamine, and pyridine; ammonium salts such as ammonium hydroxide and trimethylammonium; and ammonia; and the like, and the number of moles of 1,2-quinonediazidosulfonyl halide is zero. It is preferable to use 0.1 to 10 times, and 0.5 to 10 times.
2.0 times the number of moles is more preferably used. The condensation reaction is preferably performed at 5 to 50 ° C, more preferably 10 to 40 ° C.
C. at a temperature of .degree. The reaction time is preferably from 15 minutes to 10 hours, more preferably from about 30 minutes to 5 hours.

The composition used in the present invention contains an organic acid, in order to make the irradiated portion more easily react 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 also be contained.

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, for example, 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 halides include, for example, the ammonium salts and amine salts of the above-mentioned organic acids and the acid halides corresponding to these acids. Of these, the following formula (1) is particularly preferable.
A diazoquinone compound represented by the following formula is used.

[0029]

Embedded image

Acid generators include ultraviolet rays, far ultraviolet rays, X-rays,
A substance that generates an acid when irradiated with radiation such as an electron beam or visible light. Here, the generated acid is, for example, an inorganic acid such as sulfonic acid, phosphoric acid, iodic acid, diazoic acid, or hydrogen halide; or nitrobenzylsulfonic acid, cyanobenzylsulfonic acid, nitrobenzylcarboxylic acid, cyanobenzylcarboxylic 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 halide; halogenated hydrocarbons; phenyl nitrobenzylsulfonate, naptol nitrobenzylsulfonate, and 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-
Nitrobenzylsulfonic acid esters such as 2-sulfonate; benzoinsulfonic acid esters such as benzoin tosylate and 2-methylbenzoin tosylate; cyanobenzylsulfonic acid esters such as phenyl cyanobenzylsulfonic acid and naphthyl cyanobenzylsulfonic acid; nitrobenzylcarboxylic acid Nitrobenzyl carboxylate esters such as phenyl phenyl acid and nitrobenzyl carboxylic acid naphthol;

Cyanobenzyl carboxylate such as phenyl cyanobenzyl carboxylate and naphthyl cyanobenzyl carboxylate; nitrobenzyl phosphate such as phenyl nitrobenzyl phosphate and naphtol nitrobenzyl phosphate; phenyl cyanobenzyl phosphate and cyanobenzyl phosphate Cyanobenzyl phosphate such as acid naphthol; nitrobenzyl nitrate such as nitrobenzyl nitrate and nitrobenzyl nitrate; and cyanobenzyl nitrate such as cyanobenzyl phenyl nitrate and cyanobenzyl nitrate.

These organic acids, organic acid salts, organic acid halides and acid generators are used in an amount of 100 parts by weight of 1,2-quinonediazidesulfonic acid ester of novolak resin.
Preferably from 0.1 to 20 parts by weight, particularly preferably from 0.5 to 20 parts by weight.
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 coatability such as striation after forming a dried coating film. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether, polyethylene glycol dilaurate, polyethylene glycol distearate, and EFTOP 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.)
FC430, FC431 (manufactured by Sumitomo 3M Limited), 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 or methacrylic acid (co) polymer polyflow No. 75, No. 90, No. 95, WS (manufactured by Kyoeisha Yushi Kagaku Kogyo KK) and the like. The amount 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-quinonediazidesulfonic 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 and the like in order to visualize the latent image in the irradiated area and to reduce the influence of halation upon irradiation. it can. Preferred dyes or pigments are, for example, Neopengelb 075 (manufactured by Basf), Neozapongelb 073 (same as above), Solvent Yellow 162, SOT Yellow 3 (Hodogaya Chemical Industry Co., Ltd.)
), Macrolex Yellow (manufactured by Bayer), hydroxyazobenzene, and the like.

Preferred UV absorbers include, 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. Further, the composition used in the present invention may contain, if necessary, a storage stabilizer, an antifoaming agent and the like.

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

Examples of the organic solvent used herein 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, dimethylimidazolidinone, and the like. 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 subjected to a pre-bake treatment at a temperature of, for example, 70 to 130 ° C. in order to remove the solvent. Thereafter, the resist layer on the substrate is irradiated with radiation, for example, ultraviolet rays, far ultraviolet rays, X-rays, electron beams, visible light, or the like, only to selected portions through a pattern, for example.

By the irradiation of the radiation, the 1,2-quinonediazidosulfonyl group of the 1,2-quinonediazidesulfonic acid ester of the novolak resin is decomposed in the radiation-irradiated portion, and an acid is generated when an acid generating substance is contained. . Next, the substrate is heat-treated as 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-quinonediazidosulfonyl group present in the non-irradiated portion reacts with the novolak resin and the 1,2-quinonediazidosulfonyl group to form a crosslinked structure in the molecular chain. On the other hand, in the irradiated part, most of the 1,2-quinonediazidosulfonyl group has already been decomposed, so that the formation of a crosslinked structure is extremely small as compared with the unirradiated part.

Next, by treating with a silylating agent, the irradiated portion absorbs and reacts with the silylating agent, but the unirradiated portion absorbs and reacts with the silylating agent because of the crosslinked structure. A negative latent image which is strongly suppressed and has dry etching resistance is formed.

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; The treatment temperature of the radiation-sensitive resin layer with the silylation agent is determined by the composition of the radiation-sensitive resin layer, the type of the silylation agent used and the treatment time, and is preferably selected from 0 to 250 ° C. And more preferably from 140 to 200 ° C.

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

[0044]

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

Molecular weight in terms of polystyrene: The molecular weight in terms of polystyrene was determined by gel permeation chromatography (GPC). The measurement conditions were high-speed GPC equipment HL manufactured by Tosoh Corporation.
C-802A, detector: RI, column: TSK-GEL G4000H8, G3000 manufactured by Tosoh Corporation
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 is obtained by dividing the area of the obtained chromatogram by S ₁ and the polystyrene equivalent molecular weight by 60%.
0 The area of the following parts when the S _2, is a value determined from the following equation. 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 represented 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 of 0.6 μm in design.

Optimum exposure dose: In a pattern having a mask size of 0.6 μm, the exposure dose at which the dimension of FIG. 1A becomes 0.6 μm was determined as the optimum exposure dose.

Example 1 (1) 303 g of m-cresol, 130 g of p-cresol were placed in a flask equipped with a stirrer, a condenser and a thermometer.
276 g of a 37% by weight aqueous solution of formaldehyde and 0.756 g of oxalic acid dihydrate were charged. While stirring
The flask was immersed in an oil bath and reacted for 1 hour while maintaining the internal temperature at 100 ° C. Thereafter, 500 g of water was added, stirred, and allowed to stand for 2 minutes, and the treatment of removing the upper layer of water, unreacted monomer, unreacted formaldehyde and oxalic acid was repeated twice. After 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 novolak 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 3 g of 1,2 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 77.6 g of water in 2300 g of propylene glycol monomethyl ether acetate (hereinafter referred to as "PGMA"), 8% by weight was dissolved.
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 the mixture was allowed to stand to separate an aqueous layer and an organic layer. After discarding the aqueous layer, the same water washing operation was further performed twice to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Next, 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, 0.2 g of 1,2-naphthoquinonediazide-5-sulfonic acid was added.
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, followed by stirring until a uniform solution was obtained. Next, surfactant Megafac F172 (Dainippon Ink Co., Ltd.)
Was added and stirred.
Thereafter, the solution was filtered through a membrane filter having a pore size of 0.2 μm to prepare a solution of the composition.

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

The above silicon wafer is subjected to a magnetron-enhanced reactive ion etching apparatus (ARIES manufactured by MRC).
-C) and dry-developed 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) Observation of the pattern profile after dry development showed that a favorable pattern was obtained with b / a = 0.99 and almost no undercut. Further, the optimum exposure amount was 150 mJ / cm ² .

Comparative Example 1 (1) In a flask similar to that of Example 1 (1), 120 g of pt-butylphenol, 300 g of phenol, 86 g of paraformaldehyde, 105 g of a 37% by weight aqueous solution of formaldehyde and oxalic acid dihydrate 4. 5 g was charged. With stirring, the flask was immersed in an oil bath,
The reaction was performed for 3 hours while maintaining the temperature at 0 ° C. Thereafter, the oil bath temperature was raised to 190 ° C., and simultaneously the pressure inside the flask was reduced,
Water, unreacted phenols, formaldehyde and oxalic acid were removed. Next, the molten novolak resin was returned to room temperature and collected. Mw of the obtained novolak resin is 1
It was 4,200 and the low molecular weight component was 13.9% by weight.

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

(3) Using the esterified novolak resin obtained in (2), a solution of the composition was prepared in the same manner as in Example 1 (3). (4) A resist pattern was formed in the same manner as in Example 1 (4). (5) Observation of the pattern profile after dry development revealed that b / a was 0.80, indicating a large undercut. 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 solution of formaldehyde and oxalic acid dihydrate were added.
756 g was charged. The flask was immersed in an oil bath with stirring, and reacted for 2 hours while maintaining the internal temperature at 110 ° C. Thereafter, the temperature of the oil bath was raised to 180 ° C., and simultaneously the pressure in the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolak resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 3,800, and the low molecular weight component was 22.
% By weight.

(2) Using the novolak resin obtained in (1), 120 g of 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 /
When a = 0.96, the optimum exposure amount was 400 mJ / cm ² .

Example 3 (1) The same flask as in Example 1 (1) was charged with 216 g of m-cresol, 216 g of p-cresol, 276 g of a 37% by weight aqueous solution of formaldehyde and 0.252 g of oxalic acid dihydrate. The flask was immersed in an oil bath with stirring, and reacted for 2 hours while maintaining the internal temperature at 110 ° C. Thereafter, 600 g of water was added, and the mixture was left standing for 3 minutes after stirring. 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
The temperature was raised to 0 ° C., and simultaneously the pressure in the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolak resin was returned to room temperature and collected. The Mw of the obtained novolak resin was 2,100, and the low molecular weight component was 31% by weight.

(2) 125 g of esterified novolak resin was obtained in the same manner as in Example 1 (2) using the novolak resin obtained in (1). (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 /
When a = 0.97, the optimum exposure amount was 180 mJ / cm ² .

Example 4 (1) The same flask as in Example 1 (1) was charged with 130 g of m-cresol, 303 g of p-cresol, 260 g of a 37% by weight aqueous solution of formaldehyde and 0.756 g of oxalic acid dihydrate. The flask was immersed in an oil bath with stirring, and reacted 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. Thereafter, an operation of removing a suspension of water, unreacted cresol, formaldehyde and oxalic acid in the upper layer was performed twice.
The temperature of the oil bath was further raised to 200 ° C., and after stirring for 2 hours, the pressure in the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolak 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 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 optimal exposure amount was 300 mJ / cm ² . Was.

Example 5 25 g of the novolak resin obtained in Example 1 (1)
2-naphthoquinonediazide-5-sulfonyl chloride 1
After dissolving 0.6 g and 35 g of water in 700 g of PGMA, an 8% by weight solution of triethylamine in PGMA 5
4.9 g was added, and the mixture was stirred and reacted for 90 minutes. Then 1
4.34 ml of normal hydrochloric acid was added and stirred for 20 minutes.
After adding 250 ml of water and stirring, the mixture was allowed to stand, and an aqueous layer and an organic layer were separated. After discarding the water layer, the same washing operation is performed for two more times.
The reaction was repeated to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. The reaction solution thus washed with water was removed under reduced pressure from PGMA and water to obtain 33 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).
Next, a resist pattern was formed in the same manner as in Example 1 (4). When the pattern after dry development was observed, b
The optimum exposure was 200 mJ / cm ² at /a=0.99.

Example 6 25 g of the novolak resin obtained in Example 1 (1)
After dissolving 7.5 g of 2-naphthoquinonediazide-5-sulfonyl chloride and 20 g of water in 320 g of PGMA, an 8 wt% triethylamine PGMA solution 3
8.8 g was added, and the mixture was stirred and reacted for 90 minutes. Then 1
3.07 ml of normal hydrochloric acid was added and stirred for 20 minutes.
After adding and stirring 250 ml of a saturated aqueous solution of MA, the mixture was allowed to stand, and an aqueous layer and an organic layer were separated. The aqueous layer was discarded, and the same water washing operation was further performed twice to remove triethylamine hydrochloride, triethylamine, and hydrochloric acid remaining in the reaction solution. The reaction solution thus washed with water was removed under reduced pressure from PGMA and water 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). Next, 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 and the optimal exposure 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 added to PGMA.
After dissolving in 60 g, 0.2 g of a 10% by weight PGMA solution of Polyflow No. 90 manufactured by Kyoeisha Yushi Kagaku Kogyo KK was added and stirred. Thereafter, the solution was filtered through a membrane filter having a pore size of 0.2 μm to prepare a solution of the composition.

Next, a resist pattern was formed in the same manner as in Example 1 (4) except that the temperature of the pre-silylation baking and the silylation treatment was changed to 160 ° C. Observation of the pattern after dry development revealed that the optimum exposure amount was 220 mJ / cm ² at b / a = 0.95.

Example 8 (1) 20 g of the esterified novolak resin obtained in Example 1 (2) and 0.6 g of neopen gelp 075 (manufactured by BASF) as a dye were dissolved in 60 g of PGMA. Then one,
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 above resin solution with stirring, and the mixture was stirred until a uniform solution was obtained. Thereafter, the solution was filtered through a membrane filter having a pore size of 0.2 μm to prepare a solution of the resist composition.

Next, a resist pattern was formed in the same manner as in Example 1 (4). When the pattern after the dry development was observed, b / a was 0.99 and the optimal exposure was 140 mJ /
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 a 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 reacted for 2 hours while maintaining the internal temperature at 100 ° C. Thereafter, the temperature of the oil bath was raised to 180 ° C., and simultaneously the pressure in the flask was reduced to remove water, unreacted cresol, formaldehyde and oxalic acid. Next, the molten novolak 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)
00g, 25.3 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 15 g of water were added to 2200 g of P
After dissolution in GMA, 8% by weight of triethylamine P
131 g of the GMA solution was added, and the mixture was stirred and reacted for 90 minutes. Thereafter, 10.4 ml of 1N hydrochloric acid was added, and the mixture was stirred for 20 minutes. Then, 1 l of water was added, and the mixture was stirred and allowed to stand. The aqueous layer is discarded and the same washing operation is performed for two more times.
The reaction was repeated to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Thereafter, PGMA and water were removed from the reaction solution under reduced pressure to obtain 118 g of an esterified novolak resin.

(3) 20 g of the esterified novolak resin obtained in (2) was dissolved in 55 g of PGMA. Then
0.2 g of 1,2-naphthoquinonediazide-5-sulfonic acid
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, followed by stirring until a uniform solution was obtained. Next, surfactant Megafac F172 (Dainippon Ink Co., Ltd.)
Was added and stirred.
Thereafter, the solution 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), 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 solution of formaldehyde and 0.756 g of oxalic acid dihydrate. The flask was immersed in an oil bath with stirring, and reacted for 3 hours while maintaining the internal temperature at 110 ° C. Thereafter, 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. Next, the molten novolak resin was returned to room temperature and collected. 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)
After dissolving 2 g of 1,2 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 112 g of water in 2140 g of PGMA, 105 g of a PGMA solution of 8% by weight of triethylamine was added, and the mixture was stirred and reacted for 90 minutes. Next, 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 further performed twice to remove triethylamine hydrochloride, triethylamine and hydrochloric acid remaining in the reaction solution. Thereafter, PGMA and water were removed from the reaction solution under reduced pressure to obtain 115 g of an esterified novolak resin.

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

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

The evaluation results of Examples 1 to 9 and Comparative Examples 1 and 2 are shown in Table 1 together with 1,2-quinonediazidosulfonic acid ester of novolak resin.

[0083]

[Table 1]

[0084]

As described above, the pattern forming method of the present invention can provide a resist pattern forming method which is excellent in pattern shape and throughput without undercut.

[Brief description of the drawings]

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

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

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-96758 (JP, A) JP-A-2-254451 (JP, A) JP-A-2-185556 (JP, A) JP-A-61- 267043 (JP, A) JP-A-61-107346 (JP, A) JP-A-2-5060 (JP, A) JP-A-2-309360 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 7 / 023,7 / 38

Claims (1)

(57) [Claims] (1) A mixed cresol containing m-cresol and p-cresol is obtained by polycondensation with formaldehyde, and has a polystyrene equivalent weight average molecular weight of 1,000 to 10,000 and polystyrene. A radiation-sensitive resin composition containing a 1,2-quinonediazidosulfonic acid ester of a novolak resin containing 13% by weight or more of a low molecular weight component having a reduced molecular weight of less than 600 is applied in a layer form, and (2). Irradiate only radiation,
(3). Treating with a silylating agent vapor to selectively absorb the silylating agent into the irradiated part to cause a reaction, and (4).
A method for forming a resist pattern, wherein the layer is dry-developed by anisotropic oxygen plasma etching to selectively remove a non-irradiated portion of the layer.