JP2001027804A - Chemical amplification type resist composition and resist pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dry etching resistance and also to reduce chapping of a resist surface after dry etching by incorporating block type polyisocyanate into a resist composition. SOLUTION: A chemical amplification type resist composition contains a resin which becomes dissolvable in an alkali aqueous solution by an acid and an optical acid generating agent and further contains the block type polyisocyanate compound. The block type polyisocyanate compound is the one in which aliphatic group, aliphatic diisocyanate, diisocyanate and isocyanate of isocyanurate body in which diisocyanates are polymerized, are protected by blocking agents, and is used as a bridging agent. The resin which becomes dissolvable in the alkali aqueous solution by the acid includes a monomer unit having an alicyclic skeleton and a monomer unit having a lactone skeleton. The monomer unit having the alicyclic skeleton is selected from cyclohexyl (meth)acrylate or the like and the monomer unit having the lactone skeleton is selected from (meth)acrylate having a δ-valerolactone ring or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a chemically amplified resist composition and a method of forming a resist pattern, and more particularly to a chemically amplified resist composition and a method of forming a resist pattern suitable for fine processing using an excimer laser or an electron beam. .

[0002]

2. Description of the Related Art In recent years, in the field of microfabrication in the production of semiconductor devices or liquid crystal devices, miniaturization has rapidly progressed due to advances in lithography technology. As a method of miniaturization, a shorter wavelength of an exposure light source is generally used.
Specifically, from the ultraviolet rays represented by the conventional g-line and i-line,
It is changing to UV.

At present, a KrF excimer laser (248 n
m) lithography techniques are introduced to the market, further it is about to be introduced ArF excimer laser (193 nm) lithographic technique that measure the shorter wavelength is, F ₂ excimer laser (157 nm) lithographic technique is a further next generation technology research Have been. Also, electron beam lithography, which is a slightly different type of lithography, has been energetically studied.

As a high-resolution resist for such a short wavelength light source or an electron beam, International Business Machines (IBM) has proposed a "chemically amplified resist". Development is being actively pursued.

[0005] In addition, when the wavelength of the light source is shortened, the resin used for the resist is also required to change its structure. In KrF excimer laser lithography, 248 nm is required.
Polyhydroxystyrene having high transparency and its hydroxyl group protected by an acid dissociable, dissolution inhibiting group are used. In ArF excimer laser lithography, the above resin has insufficient transparency at 193 nm and is almost used. Since it is impossible, acryl-based resins or cycloolefin-based resins transparent at 193 nm have attracted attention. As the acrylic resin, Japanese Patent Application Laid-Open
JP-A-39665, JP-A-10-20769 and the like are mentioned, and as for the cycloolefin-based resin, JP-A-10-153864 and the like are mentioned.

However, even when these resins are used, their performance is still insufficient, and higher dry etching resistance is required.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a chemically amplified resist composition having high dry etching resistance and suitable for DUV excimer laser lithography or electron beam lithography.

[0008]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies for the purpose of improving the dry etching resistance of a chemically amplified resist composition.
DUV by adding blocked isocyanate
The present inventors have found that a chemically amplified resist composition suitable for excimer laser lithography or electron beam lithography can be obtained, and have reached the present invention.

That is, the present invention provides a chemically amplified resist composition containing a resin which becomes soluble in an aqueous alkali solution by an acid and a photoacid generator, in which the isocyanate group of diisocyanate or isocyanurate of diisocyanate is protected with a blocking agent. A chemically amplified resist composition comprising a blocked polyisocyanate compound.

The present invention also provides a method of forming a resist using the chemically amplified resist composition, irradiating the resist with actinic rays such as UV, DUV, EB and / or far infrared rays or a heat source before performing dry etching. A resist pattern forming method, wherein a heat treatment is performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The block type polyisocyanate compound used in the present invention is a diisocyanate such as an aliphatic diisocyanate or an alicyclic diisocyanate, or a compound obtained by protecting an isocyanurate group of an isocyanurate obtained by polymerization of a diisocyanate with a blocking agent. In the present invention, the block type polyisocyanate compound is used as a crosslinking agent. The block-type polyisocyanate compound can be used alone or in combination of two or more as needed.

[0012] The present inventors have found that by including a block type polyisocyanate in a resist composition, it is possible to improve dry etching resistance and to reduce roughness of the resist surface after dry etching. .

With respect to the block type polyisocyanate,
“Thermosetting resin” Vol. 13No. 2 (1992), pp. 47-59, or "Advanced Coating Technology" published by Sogo Gijutsu Center (Author: Yuji Harasaki) 191
Pp. 198, the details of which are described. The block type polyisocyanate is also referred to as a blocked isocyanate or a blocked polyisocyanate, and is a stable compound at ordinary temperature obtained by reacting a compound having a certain type of active hydrogen (blocking agent) with a polyisocyanate compound. When heated under certain conditions, the blocked polyisocyanate dissociates the blocking agent to regenerate the original active isocyanate group.

The diisocyanate compound and the isocyanurate which is a trimer of the diisocyanate are not particularly limited, but are preferably 1,6-hexamethylene diisocyanate, methylene bis (4-cyclohexyl isocyanate), trimethylhexamethylene diisocyanate,
Examples thereof include aliphatic or alicyclic diisocyanates such as isophorone diisocyanate.

Examples of the blocking agent include alcohols such as methanol, ethanol, isopropanol, n-butanol, 2-ethoxyhexanol, 2-N, N-dimethylaminoethanol, 2-ethoxyethanol and cyclohexanol; phenol; Phenols such as -nitrophenol, P-chlorophenol, o, m, p-cresol, thiols such as 1-dodecanetyl and benzenethiol, acetone oxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, cyclohexanone oxime, acetophenone oxy and benzophenone Oximes such as oximes, diethyl malonate,
Active methylene compounds such as ethyl acetoacetate and acetylacetone; and lactams such as ε-caprolactam.

Specific examples of the block type polyisocyanate include Coronate series manufactured by Nippon Polyurethane Industry Co., Ltd. and Desmodur series manufactured by Sumitomo Bayer Urethane Co., Ltd.

The amount of the block type polyisocyanate compound to be used is appropriately selected depending on the kind thereof, but is usually 0.01 to 10 parts by weight based on 100 parts by weight of the resin which becomes soluble in an aqueous alkali solution by an acid. The more the block type polyisocyanate compound is, the more the dry etching resistance is improved.

Although the structure of the block type polyisocyanate compound is not particularly limited, it may be 200 n in lithography.
When a wavelength of m or less is used as a light source, a compound having no aromatic ring is preferable.

Next, a resin which becomes soluble in an aqueous alkali solution by an acid will be described. This resin is not particularly limited as long as it has a property of being soluble in an aqueous alkali solution by an acid, and those which have been used as a resin for a chemically amplified resist composition can be used. These are arbitrarily selected depending on the light source used for lithography.

For example, when a KrF excimer laser or an electron beam is used as a light source, considering its high etching resistance,
A resin obtained by copolymerizing p-hydroxystyrene or a derivative thereof is preferably used. In that case, in order to use it as a chemically amplified resist composition, it is essential that the copolymer has a functional group which is eliminated by an acid and becomes soluble in an alkaline developer.

Specifically, a hydroxyl group of p-hydroxystyrene is protected by an acetoxy group, a t-butyl group, a tetrahydropyranyl group, a methyl adamantyl group, or the like, and a carboxyl group of a copolymerizable monomer is protected. It is preferred to do so.

When the light source is an ArF excimer laser, a resin obtained by copolymerizing p-hydroxystyrene or a derivative thereof cannot be used due to its low light transmittance because of a short wavelength. Therefore, a resin having an alicyclic skeleton is preferably used in consideration of the balance with the etching resistance.

Specifically, acrylic resins described in JP-A-9-090637 or JP-A-10-2070069, and olefin-based resins described in JP-A-10-207070 or 10-218941 are disclosed. Resins.

Among them, an acrylic copolymer obtained by polymerizing a monomer having an alicyclic skeleton and a monomer having a lactone skeleton is particularly suitable as a resin for ArF excimer laser lithography.

The monomer having an alicyclic skeleton imparts high dry etching resistance to a copolymer obtained by polymerization and its resin composition, and particularly has a protecting group which is eliminated by an acid. Those containing can also provide high sensitivity at 193 nm. Monomers having an alicyclic skeleton can be used alone or in combination of two or more as necessary.

Examples of the monomer having an alicyclic skeleton include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentadienyl (meth) At least one selected from the group consisting of acrylates and derivatives having a substituent such as an alkyl group, a hydroxyl group or a carboxyl group on the alicyclic ring of these monomers is preferable. Specifically, 1-isobonyl methacrylate, 2-methacryloyloxy-2
-Methyladamantane, cyclohexyl methacrylate, adamantyl methacrylate, tricyclodecanyl methacrylate, dicyclopentadienyl methacrylate and the like.

The monomer having a lactone skeleton imparts adhesion to a substrate to a copolymer obtained by polymerization and a resin composition thereof, and particularly contains a protective group which is released by an acid. Those can provide high sensitivity at 193 nm. Monomers having a lactone skeleton can be used alone or in combination of two or more as needed.

Examples of the monomer having a lactone skeleton include (meth) acrylate having a δ-valerolactone ring, (meth) acrylate having a γ-butyrolactone ring, and At least one selected from the group consisting of derivatives having a substituent such as an alkyl group, a hydroxyl group, and a carboxyl group is preferable.

Specifically, β-methacryloyloxy-β-
Methyl-δ-valerolactone, β-methacryloyloxy-γ-butyrolactone, β-methacryloyloxy-
β-methyl-γ-butyrolactone, α-methacryloyloxy-γ-butyrolactone, 2- (1-methacryloyloxy) ethyl-4-butanolide, pantolactone methacrylate and the like.

The weight average molecular weight of the resin soluble in an aqueous alkali solution with an acid is not particularly limited, but is preferably 1,0.
The range is from 00 to 100,000. The larger the weight average molecular weight, the better the dry etching resistance and the better the resist shape, and the smaller the weight average molecular weight, the better the solubility in the resist solvent and the better the resolution.

As a method for producing a resin which becomes soluble in an alkaline aqueous solution by an acid, for example, an organic solvent in which a monomer solution obtained by dissolving a monomer and a polymerization initiator in an organic solvent is maintained at a predetermined temperature is used. A so-called drop polymerization method in which the solution is dropped into the inside is simple and suitable.

The organic solvent used in the drop polymerization method is not particularly limited, but is preferably a solvent that can dissolve both the monomer and the obtained copolymer, and examples thereof include 1,4-dioxane, isopropyl alcohol, acetone, and tetrahydrofuran. Is mentioned.

[0033] The polymerization initiator used in the drop polymerization method is not particularly limited. For example, azobisisobutyronitrile,
Examples include azo compounds such as 2,2'-azobis (2,4-dimethylvaleronitrile) and organic peroxides such as benzoyl peroxide. N-butyl mercaptan, n
-Mercaptans such as octyl mercaptan may be used in combination as a chain transfer agent.

[0034] The polymerization temperature in the drop polymerization method is not particularly limited, but is preferably in the range of 50 to 150 ° C. The dropping time is not particularly limited, but is 6 hours or more, and it is preferable to maintain the temperature for about 2 hours after the completion of the dropping to complete the polymerization.

A resin solution which is made soluble in an aqueous alkali solution by an acid produced by the drop polymerization method is diluted with a good solvent such as tetrahydrofuran or 1,4-dioxane to an appropriate solution viscosity, and then heptane, methanol, It is deposited by dropping into a large amount of poor solvent such as water. Thereafter, the precipitate is separated by filtration and dried sufficiently. This step is called reprecipitation, and may be unnecessary in some cases. However, it is very effective for removing unreacted monomers or a polymerization initiator remaining in the polymerization solution. If these unreacted substances remain as they are, they may adversely affect the resist performance. Therefore, it is preferable to remove these unreacted substances if possible.

Thereafter, the resin powder which becomes soluble in the aqueous alkali solution by the dried acid is dissolved in the solvent. This solvent
The solvent is arbitrarily selected depending on the purpose, but the choice of the solvent is also restricted by reasons other than the solubility of the resin, for example, the uniformity, appearance, safety and the like of the coating film.

As a solvent satisfying these conditions, for example,
Linear ketones such as 2-pentanone and 2-hexanone;
Cyclic ketones such as cyclopentanone and cyclohexanone; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; ethylene glycol monoethylene such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate Alkyl ether acetates; propylene glycol monomethyl ether,
Propylene glycol monoalkyl ethers such as propylene glycol monoethyl ether; ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; diethylene glycol alkyl ethers such as diethylene glycol dimethyl ether and diethylene glycol diethyl ether; ethyl acetate, lactic acid Esters such as ethyl; alcohols such as cyclohexanol and 1-octanol; ethylene carbonate and γ-butyrolactone. These solvents can be used alone or in combination of two or more.

Next, the photoacid generator used in the present invention will be described. The photoacid generator can be arbitrarily selected from those which can be used as an acid generator for a chemically amplified resist composition. The photoacid generators can be used alone or in combination of two or more.

Specific examples include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonate compounds, quinonediazide compounds and diazomethane compounds. Among them, onium salt compounds are preferred,
For example, sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts and the like can be mentioned.

As specific examples, triphenylsulfonium triflate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium naphthalene sulfonate, (hydroxyphenyl) benzylmethylsulfonium toluenesulfonate, diphenyliodonium triflate, diphenyliodonium pyrene sulfonate, diphenyliodonium Dodecylbenzene sulfonate, diphenyliodonium hexafluoroantimonate and the like can be mentioned.

The amount of the photoacid generator used is appropriately determined depending on the type of the photoacid generator used, and is usually 0.1 to 20 parts by weight, preferably 100 parts by weight, per 100 parts by weight of the resin which becomes soluble in an aqueous alkali solution by an acid. Is 0.5 to 10 parts by weight. If the amount of the photoacid generator is too small, it may be difficult to sufficiently generate a chemical reaction due to the catalytic action of the acid generated by exposure, and if the amount is too large, the stability of the resist composition decreases. Or unevenness in application of the composition, or scum or the like during development.

Further, various additives such as a surfactant, a quencher, a sensitizer, an antihalation agent, a storage stabilizer, and an antifoaming agent may be added to the chemically amplified resist composition of the present invention, if necessary. You can also.

Examples of the surfactant include nonionic surfactants such as polyoxyethylene lauryl ether and polyethylene glycol dilaurate. 75 (manufactured by Kyoeisha Yushi Kagaku Kogyo),
Megafax F173 (manufactured by Dainippon Ink and Chemicals),
Surflon SC-105 (made by Asahi Glass), L-70001
(Manufactured by Shin-Etsu Chemical Co., Ltd.).

Next, a method of using the chemically amplified resist composition of the present invention will be described. During pre-bake (soft bake) after resist coating or PEB (post-exposure bake) after exposure, the blocking agent comes off, and if isocyanate is regenerated, the resolution may be reduced. Therefore, when performing pre-baking or PEB, a blocking agent having a dissociation temperature higher than the heat treatment temperature may be selected, or the heat treatment may be performed at a temperature lower than the dissociation temperature of the blocking agent.

When a pattern is formed using the chemically amplified resist composition of the present invention, the formed resist is
Before dry etching, irradiation with actinic rays such as UV, DUV and EB and / or heat treatment for a certain period of time using a heat source such as far infrared rays or a hot plate may dissociate the blocking agent to regenerate polyisocyanate groups. preferable. The details of the mechanism of action of this treatment are unknown, but an acid is generated from the photoacid generator by irradiation with actinic rays or an electron beam, and a hydroxyl group or a carboxyl group generated by removing the protective group of the resist resin, and a polyisocyanate. It is presumed that it reacts with a group to form a three-dimensional cross-linked structure and has improved dry etching resistance.

Therefore, it is most preferable to perform a heat treatment by irradiating an actinic ray again after forming a pattern by exposure, PEB and development.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Here, “parts” means “parts by weight” unless otherwise specified. The measurement of the physical properties of the copolymer and the evaluation of the resist were performed by the following methods.

<Weight average molecular weight> Gel permeation
It was determined by chromatography (GPC) in terms of polymethyl methacrylate. Chloroform or tetrahydrofuran was used as the solvent.

<Average copolymer composition (mol%) of copolymer> ¹ H
-Determined by NMR measurement. Heavy chloroform or heavy acetone was used as the solvent.

<Sensitivity> Immediately after exposing the resist film formed on the silicon wafer, post-exposure baking was performed, then developed with an alkali developing solution, washed with water, and dried to form a resist pattern. The exposure was measured as the sensitivity to form a line and space pattern (L / S = 1/1) with a line width of 1/1.

<Resolution> The minimum dimension (μm) of the resist pattern resolved when exposed at the above exposure amount was defined as the resolution.

<Dry Etching Resistance> The resist film formed on the silicon wafer was etched, and the etching rate of each resist (normalized with the etching rate of novolak resin as 1) was measured from the decrease in film thickness. Etching conditions were as follows: using an etching machine manufactured by Tokyo Electron, using a gas mixture of C ₄ F ₈ / Ar / O _{2 as a} gas;
The operation was performed at 00 W and 50 mTorr for 50 seconds.

Further, the resist surface after etching was observed with an electron microscope, and the resist surface having no irregularities was evaluated as “「 ”, and the one having irregularities and rough was evaluated as“ X ”.

(Synthesis Example 1) A flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer was placed in a nitrogen atmosphere under a nitrogen atmosphere.
20.0 parts of 1,4-dioxane was added, and the temperature of the hot water bath was raised to 80 ° C. while stirring. pt-butoxystyrene (abbreviation: PTBST, molecular weight = 176) 22.0 parts, p-hydroxystyrene (abbreviation: HS, molecular weight = 120) 15.0
, 62.5 parts of 1,4-dioxane and 1.9 parts of azobisisobutyronitrile were dropped into the flask at a constant rate over 6 hours, and then the temperature was 80 ° C. For 2 hours. Then, the obtained reaction solution was diluted about 2-fold with tetrahydrofuran, and added dropwise to about 10-fold amount of water while stirring to obtain a white precipitate (copolymer A-
A precipitate of 1) was obtained. The resulting precipitate is filtered off and dried under reduced pressure.
Dried at 40 ° C. for about 40 hours.

Next, each physical property of the obtained copolymer A-1 was measured. The weight average molecular weight was 12,000, and the copolymer composition ratio was PTBST / HS = 51/49 mol%.

(Synthesis Example 2) A flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer was placed under a nitrogen atmosphere.
20.0 parts of 1,4-dioxane was added, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 2-methacryloyloxy-2-methyladamantane (abbreviation: MAdMA, molecular weight
= 234) 29.3 parts, β-methacryloyloxy-γ-butyrolactone (abbreviation: HGBMA, molecular weight = 170)
A monomer solution obtained by mixing 2 parts, 62.5 parts of 1,4-dioxane, and 1.9 parts of azobisisobutyronitrile was dropped into the flask at a constant speed over a period of 6 hours.
Was maintained for 2 hours. Then, the obtained reaction solution was diluted about 2-fold with tetrahydrofuran, and added dropwise to about 10-fold amount of methanol with stirring to obtain a white precipitate (copolymer A-2). The obtained precipitate was separated by filtration and dried under reduced pressure at 60 ° C. for about 40 hours.

Next, each physical property of the obtained copolymer A-2 was measured. The weight average molecular weight was 11,000, and the copolymer composition ratio was MAdMA / HGBMA = 50/50 mol%.

Examples 1 to 4 and Comparative Examples 1 to 2 The components shown in Table 1 were mixed to form a uniform solution, which was then filtered through a membrane filter having a pore size of 0.1 μm to prepare a resist composition solution. Thereafter, each composition solution was spin-coated on a silicon wafer, and then prebaked at 120 ° C. for 60 seconds using a hot plate to form a 0.5 μm-thick resist film. Then, KrF
After exposure using an excimer laser exposure machine or an ArF excimer laser exposure machine, a post-exposure bake was performed at 120 ° C. for 60 seconds using a hot plate. Then
The resist was developed with a 2.38% by weight aqueous solution of tetramethylammonium hydroxide at room temperature, washed with pure water, and dried to form a resist pattern. Tables 2 and 3 show the evaluation results of the obtained resist patterns.

Then, using an ultra-high pressure mercury lamp, about 500 mJ
/ Cm ² of ultraviolet light and 180 ° on a hot plate.
Heat treatment was performed at 60 ° C. for 60 seconds. Tables 2 and 3 show the results of measuring the etching rate of each resist under the conditions described above.

As described above, in the examples, the dry etching resistance was improved without significantly lowering the sensitivity and the resolution, and the resist surface after etching was not roughened. On the other hand, in the comparative example, the dry etching resistance was not sufficient, and the surface of the resist after etching was rough.

[0061]

【table 1】

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

As described above, the chemically amplified resist composition of the present invention comprises:
Roughness of the resist surface after etching does not occur, dry etching resistance is good, sensitivity and resolution are high, and a high-precision fine resist pattern can be stably formed. Therefore, for DUV excimer laser lithography and electron beam lithography, especially ArF
It can be suitably used for lithography using an excimer laser.

By using the pattern forming method of the present invention, higher dry etching resistance can be obtained.

Continued on the front page F term (reference) 2H025 AA01 AA02 AA09 AB16 AC04 AC06 AD03 BE00 BE10 CB14 CB15 CB41 CC17 FA17 FA29 FA41 4J034 BA03 DA01 DB03 DB07 DP03 DP18 HA01 HA07 HC03 HC17 HC22 HC26 HC35 HC46 HC52 HC61 HC64 HC67 HC71 HC73 HD73 HD06 HD07 HD12 HD15 JA21 KA01 KB02 KB04 KC23 KD11 KD14 KD21 KD24 KE02 LA23 LA33 QB11

Claims (5)

[Claims] Claims: 1. A chemically amplified resist composition containing a resin soluble in an aqueous alkali solution by an acid and a photoacid generator, wherein a block type polyisocyanate or a block type polyisocyanate isocyanurate isocyanate group protected with a blocking agent. A chemically amplified resist composition comprising an isocyanate compound. 2. The resist resin according to claim 1, wherein the resist resin soluble in an alkaline aqueous solution by an acid contains a monomer unit having an alicyclic skeleton and a monomer unit having a lactone skeleton. Chemically amplified resist composition. 3. The monomer unit having an alicyclic skeleton includes cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and dicyclopentadienyl ( 3. The chemically amplified resist composition according to claim 2, wherein the composition is at least one selected from the group consisting of meth) acrylates and derivatives thereof having a substituent on an alicyclic ring. 4. The monomer unit having a lactone skeleton is represented by δ
A (meth) acrylate having a valerolactone ring, γ
The chemical amplification according to claim 2 or 3, wherein the compound is at least one selected from the group consisting of (meth) acrylate having a -butyrolactone ring and derivatives of these monomers having a substituent on the lactone ring. -Type resist composition. 5. A resist is formed using the chemically amplified resist composition according to claim 1, and the resist is irradiated with actinic rays such as UV, DUV, EB and / or far infrared rays before performing dry etching. Alternatively, a method for forming a resist pattern, comprising performing heat treatment with a heat source.