JPH1073919A - Photosensitive resin composition containing optical acid generating agent having crosslinked cyclic alkyl group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive resin composition usable for far ultraviolet ray having a wavelength of 220nm or less by containing an optical acid generating agent formed of a specified alkyl sulfonium salt compound as the component. SOLUTION: This photosensitive resin composition contains an optical acid generating agent formed of a specified alkyl sulfonium salt compound as the component. Namely, the alkyl sulfonium salt compound used in the optical acid generating agent is represented by the formula. In the formula, at least one of R<1> , R<2> represents an alkyl group having a crosslinked cyclic hydrocarbon group or a monocyclic alkyl group, and the remainder represents a straight chain, branched, or monocyclic alkyl group. R<3> represents a monocyclic alkyl group having an oxo group in β-position or a crosslinked cyclic alkyl group having an oxo group in β-position. Y represents a pair ion. In this pattern forming method, the photosensitive resin composition is used, and patterning is performed by light emission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive resin composition containing a photoacid generator comprising a novel sulfonium salt compound and a method for forming a pattern using the same. Below 180nm
The present invention relates to a photosensitive composition suitable for the case where far ultraviolet rays are used as exposure light.

[0002]

2. Description of the Related Art In recent years, in the field of manufacturing various electronic devices that require microfabrication of semiconductor elements, integrated circuits, and the like, demands for high density and high integration of devices are increasing. For this reason, the demand for photolithography technology for realizing pattern miniaturization is becoming increasingly severe.

One method of miniaturizing a pattern is to shorten the wavelength of exposure light used in forming a pattern on a photoresist. Generally, the resolution (line width) R of an optical system can be represented by Rayleigh's formula, R = k · λ / NA (where λ is the wavelength of an exposure light source, NA is the numerical aperture of a lens, and k is a process factor). . From this equation, it can be seen that higher resolution can be achieved, that is, the value of R can be reduced by shortening the wavelength λ of the exposure light in lithography. For example, DR with an integration degree of up to 64M
AM (Dynamic Random Access Memory)
In the manufacture of, a minimum pattern size of 0.35 μm line-and-space resolution is required, and g-line (438 nm) and i-line (365 nm) of a high-pressure mercury lamp have been used as a light source until now. However, in the manufacture of a DRAM having a degree of integration of 256 M or more (processing size of 0.25 μm or less) requiring finer processing technology, an excimer laser (K
rF: 248 nm, KrCl: 222 nm, ArF: 193
It is considered that the use of shorter wavelength light (deep UV light, far ultraviolet light) such as F. nm, F2: 157 nm is effective (Takumi Ueno, Takao Iwayanagi, Saburo Nonogaki, Hiroshi Ito, Hiroshi Ito, C.I.
Grant Wilson (C. Grant Wills)
on) co-author, "Short Wavelength Photoresist Material-Microfabrication for ULSI", pp. 172 to 197, Bunshin Publishing, 1988), and KrF excimer laser lithography is currently being actively studied.

As for the photoresist, a method of high integration by using a multi-layer (two-layer or three-layer) resist method instead of the conventional single-layer resist is being studied. 2
As the layer resist, for example, Journal of Vacuum Science and Technology (Journ)
al of Vacuum Science andT
Wilkins, described in B3, pp. 306-309 (1985).
Kins) et al. (a two-layer resist using a silylated novolak resin for the upper layer).

[0005] Further, in addition to high resolution corresponding to miniaturization of processing dimensions, resist materials used for microprocessing are required.
The demand for higher sensitivity is increasing. This is because it is necessary to improve the cost performance of the laser because the gas life of the excimer laser, which is the light source, is short and the laser device itself is expensive. As a method for increasing the sensitivity of a resist, development of a chemically amplified resist using a photoacid generator as a photosensitive agent has been studied in detail as a resist for a KrF excimer laser [for example, Hiroshito, C.I. Grant Wilson (Gr
ant Willson), American Chemical Society Symposium Series (America)
n Chemical Society Sympos
iumSeries), 242, 11 to 23 (1
984)]. A photoacid generator is a substance that generates an acid upon irradiation with light. The characteristic of the chemically amplified resist is that the proton acid generated by the photoacid generator as a contained component is subjected to a heat treatment after exposure (post-exposure bake (Post Ex).
(Positive Bake, hereinafter abbreviated as PEB step) is to move in the resist solid phase, and to amplify the chemical change of the resist resin or the like by catalytic reaction several hundred times to several thousand times by the acid. In this way, the photoreaction efficiency (reaction per photon) is significantly higher than that of a conventional resist having less than 1. Examples of currently used photoacid generators include, for example, the Journal of the Organic Chemistry (Journal of the Organic Chemistry).
heOrganic Chemistry), 43 volumes,
No. 15, pages 3055 to 3058 (1978). V. Crivello (JV Crivell)
o) triphenylsulfonium salt derivatives, 2, 6
-Dinitrobenzyl esters [T. X. TX Neenan et al., SPIE Proceedings, 1086, 2-10 (1989) (Proc.
eating of SPIE, vol 1086, p
p. 2-10 (1989))], 1,2,3-tri (methanesulfonyloxy) benzene [Takumi Ueno et al.
Proceeding of PME '89, Kodansha, 41
3-424 (1990)].

At present, most of resists to be developed are of the chemical amplification type, and the use of a chemical amplification mechanism is indispensable for the development of a high-sensitivity material corresponding to a shorter wavelength of an exposure light source.

[0007]

One of the current technical problems in this field is that light having high transparency to far ultraviolet light of 220 nm or less and high photoreaction efficiency (photoacid generation efficiency). An object of the present invention is to develop a chemically amplified resist material using an acid generator and to develop a method for forming a pattern using the resist material.

In other words, a chemically amplified resist for a single layer, which is widely used at present, is used, and 220 μm is used for pattern miniaturization.
When an exposure light having a wavelength shorter than nm, for example, an ArF excimer laser (193 nm) is used, it is general that the absorption of the exposure light by the resist becomes extremely strong. Therefore, 0.
Most light is absorbed in the vicinity of the surface on the exposure light incident side of the single-layer resist having a film thickness of about 7 to 1.0 μm,
Light hardly reaches the resist portion near the substrate. For this reason, there is a problem that the photosensitive portion near the substrate is hardly exposed to light and the pattern is not separated. For this reason,
In lithography using an ArF excimer laser as a light source, which is currently expected to be a next-generation light source of KrF, the current resist does not resolve a pattern at all.

In the case of the base polymer compound (resin) in the resist, the base height of a novolak resin, which is a polymer compound used in most current i-line resists, or the base height of a chemically amplified resist currently used for KrF excimer laser exposure. Poly (p-vinylphenol), which is widely used as a molecular compound, has an aromatic ring in its molecular structure and exhibits dry etching resistance based on the aromatic ring. These resins have a strong absorption in a shorter wavelength region than the KrF excimer laser (248 nm). For this reason, it cannot be used as a lithography resist that uses light having a shorter wavelength than the KrF excimer laser, more specifically, light having a wavelength of 220 nm or less as exposure light. An alicyclic polymer (a copolymer of adamantyl methacrylate and tert-butyl methacrylate) has recently been reported as a resin having a wavelength of 220 nm or less and having dry etching resistance [Takechi et al., Journal of Photopolymer.・ Science ・
And Technology (Journal of Pho
toppolymer Science and Tec
hnology), 5 (3), 439-446 (1992)].

There is a similar problem in the case of a photosensitive agent. Kr
The photosensitive agent used in conventional lithography using exposure light having a longer wavelength than the wavelength of the F excimer laser light is 220 nm.
There is a similar problem that the following light absorption is strong and cannot be used for a lithography resist of 220 nm or less. For example, photoacid generators such as the triphenylsulfonium salt derivative of Krivero et al., Which are typical photosensitizers (photoacid generators) of chemically amplified resists, each have an aromatic ring in their structure. Therefore, it strongly absorbs light of 220 nm or less. For this reason, the current photoacid generators for the above reasons are:
It cannot be used for a chemically amplified resist using light having a wavelength of 220 nm or less, which can be expected to have higher resolution, as exposure light.

Although there are few reports of polymer compounds for lithography at a wavelength of 220 nm or less as described above, there is a report of a small number of such compounds, but they are indispensable for improving the cost performance of lasers that can be combined with these polymer compounds. There have been few reports of developing photoacid generators indispensable for the expression of chemical amplification. In order to solve this problem, the present inventors have already developed and applied for a novel photosensitizer (photoacid generator) having high transparency and high photoreactivity in the wavelength region of 180 nm to 220 nm. 5-1
74528). The photosensitive resin composition containing the invented compound has been demonstrated to have high resolution in lithography using an ArF excimer laser as exposure light (Japanese Patent Application No. 5-174532). By the way, the heating temperature in various processes generally used in a lithography process using a chemically amplified photosensitive resin composition (a prebake (PB) process, a PEB process, etc.) is usually 80 to 120.
It is preferable that the components constituting the photosensitive resin composition are stable at these process temperatures. Generally, the higher the processing temperature, the better. The high temperature treatment can be expected to promote the removal of the solvent by heating in the PB step and to increase the chemical amplification efficiency in the PEB step. These are extremely important from the practical viewpoint of not only achieving high resist resolution in lithography but also reducing the cost of exposure light (such as an ArF excimer laser) by increasing the chemical amplification efficiency. Further, the wafer on which a pattern is formed in a semiconductor manufacturing process is generally subjected to a baking process at a temperature of 100 to 120 ° C. in order to remove moisture and a solvent in the resist before the etching process. For this reason, the photosensitive resin composition as the pattern forming material needs to exhibit stability without breaking the shape even in this baking treatment. Therefore,
There is a further need for the development of photosensitive resin compositions and their component materials (especially photosensitive agents (photoacid generators)) that can be processed at higher temperatures in the lithography process.

[0012]

The inventors of the present invention have made intensive studies and as a result, have found that the above technical problem has been solved by a photosensitive resin composition containing a photoacid generator comprising an alkylsulfonium salt compound having the structure disclosed below and The present invention has been found to be solved by a patterning method characterized in that patterning is performed by light irradiation using the photosensitive resin composition.

The alkylsulfonium salt compound used for the photoacid generator of the photosensitive resin composition of the present invention is represented by the following general formula (1).

[0014]

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However, in the general formula (1), R ¹ and R ²
At least one of which is a C 7 to C 12 alkyl group having a C 7 to C 10 bridged cyclic hydrocarbon group (more specifically, a norcalanyl group (bicyclo [5.
1.0] heptyl group), norpinanyl group (bicyclo [3.1.0] heptyl group), norbornyl group (bicyclo [2.2.1] heptyl group), adamantyl group, bicyclo [2.2.2] octyl Group, bicyclo [3.2.
1] octyl group, tricyclo [2.2.1.0 ^2,6 ] heptyl group, tricyclo [5.2.1.0 ^2,6 ] decanyl group, tricyclo [5.3.1.1 ^2,6 ] A dodecyl group, a tricyclo [4.4.1.1 ^1,5 ] dodecyl group, a calanyl group, a pinanyl group, a bornyl group, and the like. ), The remainder being a linear, branched or monocyclic alkyl group having 1 to 7 carbon atoms (more specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec- Butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclopropylmethyl group,
Represents a 4-methylcyclohexyl group or a cyclohexylmethyl group. ), R ³ is β-C 5-7
An oxo monocyclic alkyl group (more specifically, a β-oxocyclopentyl group, a β-oxocyclohexyl group, or a β-oxocycloheptyl group is more preferable because of availability of raw materials or low cost).

Alternatively, at least one of R ¹ and R ² is a monocyclic alkyl group having 5 to 7 carbon atoms (more specifically, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a 4-methylcyclohexyl group or a cyclohexyl group). Represents a methyl group, etc.), and the remainder is a linear, branched or monocyclic alkyl group having 1 to 8 carbon atoms (more specifically, methyl, ethyl, n-propyl, isopropyl, n -Butyl group, sec-butyl group, ter
t-butyl group, pentyl group, hexyl group, heptyl group,
Represents an octyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclopropylmethyl group, a 4-methylcyclohexyl group, a cyclohexylmethyl group, or the like. ), R ³ is a bridged cyclic alkyl group having 7 to 10 carbon atoms having an oxo group at the β-position (more specifically,
-Oxonorcalanyl group (β-oxobicyclo [5.
1.0] heptyl group), β-oxonorpinanyl group (β
-Oxobicyclo [3.1.0] heptyl group), β-oxonorbornyl group (β-oxobicyclo [2.2.
1] heptyl group), β-oxoadamantyl group, β-oxobicyclo [2.2.2] octyl group, β-oxobicyclo [3.2.1] octyl group, β-oxotricyclo [2.2. 1.0 ^2,6 ] heptyl group, β-oxocaranyl group, β-oxopinanyl group, β-oxobornyl group and the like. ).

Y￣ represents a counter ion, and more specifically,
BF ₄ ￣ (tetrafluoroborate ion), AsF
₆ ¯ (hexafluoroarsenate ion), SbF
₆ ¯ (hexafluoroantimonate ion), PF
₆ ¯ (hexafluorophosphate ion), CF ₃
SO ₃ ¯ (trifluoromethanesulfonate ion), CH ₃ SO ₃ ¯ (methanesulfonate ion), ClO ₄ ¯ (perchlorate ion), Br (bromine ion), Cl (chlorine ions) or I¯ [Iodine ion] etc. [Inhibition of contamination of impurity ions in the manufacture of integrated circuits or suppression of scattering and disappearance of protonic acid from the resist in the heat treatment (PEB) applied in the resist pattern forming process. From the viewpoint, BF ₄ ￣ (tetrafluoroborate ion), AsF ₆ ￣ (hexafluoroarsenate ion), SbF ₆ ￣ (hexafluoroantimonate ion) and PF ₆ ￣ (hexafluorophosphate) Ion) and CF ₃ SO ₃ ￣ (trifluoromethanesulfonate ion) are more preferred] .

In particular, among the sulfonium salts which are constituents of the photosensitive resin composition of the present invention, R ¹ is a norbornyl group, an adamantyl group, or β-oxonorbornane-2-.
One of the yl groups, R ² is a methyl group, R ³
Are sulfonium salt compounds having a β-oxocyclohexyl group or a cyclohexyl group.

The sulfonium salt represented by the general formula (1) used as a photoacid generator, which is a component of the photosensitive resin composition of the present invention, is, for example, a journal of the American Chemical Society (Journal of the American Chemical Society). Journal
of the American Chemical
Society) 108 (7), 1579-1
DN Kevil for the sulfonium salts described on page 585 (1986).
1) It can be manufactured by applying the method of the above. In the case of the photosensitive compound represented by the general formula (1), a sulfide derivative represented by the general formula (2), the general formula (3), or the general formula (4), for example, a nitromethane solution is subjected to the general formula (5) or the general formula (5). An excess amount of the alkyl halide represented by the formula (6) or the general formula (7) (2 to 100 times (more preferably 5 to 20 times) the mol of the sulfide unit of the sulfide derivative) is added at room temperature to 0.5 mol. ~ 5 hours (preferably 1-2
Time) to react. Thereafter, a solution of an organic acid metal salt represented by the general formula (8) dissolved in nitromethane in an equimolar amount with respect to the sulfide unit of the sulfide derivative is added, and the mixture is further reacted at room temperature to 50 ° C. for 3 to 24 hours. Thereafter, the insoluble metal salt is separated by filtration, and the filtrate is concentrated, and then poured into a large amount of a poor solvent such as diethyl ether for reprecipitation. The target sulfonium salt compound (general formula (1)) can be obtained by repeating the operation of dissolving the obtained crystals in acetone and reprecipitating in diethyl ether several times.

R ¹ -SR ² (2) (wherein R ¹ and R ² are the same as above) R ² -SR ³ (3) (where R ² and R ³ are the same as above) R ¹ -SR ³ (4) (wherein R ¹ and R ³ are the same as above) R ¹ -W (5) (where R ¹ is the same as above, W is a halogen atom such as iodine and bromine) R ² -W (6) (wherein R ^2, W mother the same) R ³ -W (7) (wherein R ^3, W have the same meanings as defined ^{above) M + Y - (8)} ( wherein, M ⁺ Is Ag ⁺ , Y ^- is the same as above)

The sulfonium salt compound having a bridged cyclic alkyl group obtained in this manner can be used as a known photoacid generator (triphenylsulfonium trifluoromethanesulfonate (hereinafter abbreviated as TPS) described in the above document by Krivero et al. ), It was confirmed that light absorption in the far ultraviolet region of 180 nm to 220 nm was remarkably small.

In addition, these sulfonium salt compounds having a bridged cyclic alkyl group may be irradiated with radiation such as deep ultraviolet light or excimer laser (wavelength of 220 nm or less, preferably 180 nm to 180 nm).
Irradiation with far ultraviolet light (220 nm) confirmed that a protonic acid was generated.

Accordingly, a sulfonium salt compound having a bridged cyclic alkyl group is suitable as a photosensitizer for a photoresist (photosensitive resin composition) or an initiator for cationic photopolymerization utilizing short-wavelength light.

Further, the decomposition onset temperature of the sulfonium salt compound having a bridged cyclic alkyl group is higher than 150 ° C., and therefore, the processing temperature in the lithography step of the photosensitive resin composition using the compound is set to 150 ° C. It is possible to increase to near.

The photoacid generator [triphenylsulfonium trifluoromethanesulfonate (hereinafter abbreviated as TPS) described in the above document by Krivero et al.] Developed for KrF excimer laser lithography has extremely strong light absorption in the deep ultraviolet region of 220 nm or less. Has the property. Therefore, when used for a resist for ArF excimer laser lithography, the transparency of the resist is significantly reduced. When compared with this TPS, each of the above sulfonium salt derivatives described in the present invention has a remarkably low light absorption in the far ultraviolet region of 185.5 to 220 nm.
Obviously, it is suitable as a component of a resist for rF excimer laser lithography.

The basic constituents (components) of the photosensitive resin composition of the present invention are the alkylsulfonium salt compounds, polymer compounds and solvents described in the present invention.

It is characterized by containing a sulfonium salt having a bridged cyclic alkyl represented by the general formula (1) and a polymer compound capable of transmitting at least 40% of light having a wavelength of 180 to 220 nm in a thin film having a thickness of 1 μm. In the photosensitive resin composition of the present invention, the alkylsulfonium salt compound represented by the general formula (1) may be used alone,
A mixture of more than one species may be used. In the photosensitive resin composition of the present invention, the content of the alkylsulfonium salt compound represented by the general formula (1) is usually 0.1 to 40 parts by weight based on 100 parts by weight of a total solid content including itself. , Preferably 0.5 to 25 parts by weight. If the content is less than 0.1 part by weight, the sensitivity of the present invention is remarkably reduced, and it is difficult to form a pattern. On the other hand, when the amount exceeds 40 parts by weight, it becomes difficult to form a uniform coating film, and there is a problem that a residue (scum) is easily generated after development. Further, the content of the polymer compound of the present invention is 60 to 99.9 parts by weight, preferably 75 to 99 parts by weight, based on the total solid content including itself.

The high molecular compound which is a component of the present invention includes:
High transparency in the deep ultraviolet region of 220 nm or less,
In addition, a polymer having a functional group and a group unstable to an acid can be appropriately set and used. That is, for example, a polymer compound represented by the general formula (9) or (10) can be used.

[0029]

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[In the above formula, n is 5 to 1000.
A positive integer of (more preferably 10 to 200), R ⁴
Is a monocyclic or bridged cyclic hydrocarbon 1 shown in Table 1.
Valent group (specifically, tricyclo [5.2.1.0 ^2,6 ]
A decanyl group, a norbornyl group, an adamantyl group, or a cyclohexyl group), R ⁵ is a tert-butyl group,
A methyl group, an ethyl group, a propyl group, a tetrahydropyran-2-yl group, a tetrahydrofuran-2-yl group or a 3-oxocyclohexyl group, R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom or a methyl group, x + y + z
= 1, x is 0.1 to 0.9 (more preferably 0.3 to 0.9)
To 0.7), y is 0.1 to 0.7 (more preferably 0.3 to 0.5), and z is 0.01 to 0.5.
7 (more preferably 0.05 to 0.3). ]

[0031]

[Table 1]

Further, a high molecular compound mixture containing a plurality of the following formulas (10) as constituents can also be used.

[0033]

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[In the above formula, R ⁶ and R ⁷ are the same as above. R ⁹ is a hydrogen atom, a tert-butoxycarbonyl group, a tetrahydropyran-2-yl group, a tetrahydrofuran-2-yl group, a methyl group, an ethyl group, a propyl group,
a tert-butyl group or a 3-oxocyclohexyl group, R ¹⁰ and R ¹¹ are each independently a C 7 to C 12 hydrocarbon residue having an alicyclic hydrocarbon group;
1 to 0.99 (more preferably 0.4 to 0.8), m is 5 to 1000 (more preferably 10 to 200)
Represents a positive integer. ]

R ¹⁰ and R ¹¹ are a divalent group of a hydrocarbon having 7 to 12 carbon atoms having a bridged cyclic hydrocarbon group as shown in Table 2, and more specifically, for example, tricyclo [ 5.2.1.0 ^2,6 ] decane-4,8-dimethylene group, norbornane-2,6-dimethylene group, tricyclo [5.2.1.0 ^2,6 ] decanediyl group, adamantanediyl group, norbornane -2,3-diyl group, norbornane-2,3-dimethylene group, norbornane-2,5-
Dimethylene group, bicyclo [2.2.2] octene-2,
3-dimethylene group, and the like.

[0036]

[Table 2]

Further, the general formula (9) or the general formula (1)
A polymer compound mixture containing a plurality of the polymer compounds represented by the formula (0) as constituents can also be used.

Preferred examples of the solvent used in the present invention are organic solvents in which components consisting of a polymer compound and an alkylsulfonium salt are sufficiently dissolved, and the solution is capable of forming a uniform coating film by spin coating. Any solvent may be used as long as it is used. Moreover, you may use individually or in mixture of 2 or more types. Specifically, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert
-Butyl alcohol, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monoethyl ether acetate, methyl lactate, ethyl lactate,
2-methoxybutyl acetate, 2-ethoxyethyl acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, N
-Methyl-2-pyrrolidinone, cyclohexanone, cyclopentanone, cyclohexanol, methyl ethyl ketone, 1,4-dioxane, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether , Diethylene glycol dimethyl ether, and the like, but are not limited thereto.

The "basic" constituents of the photosensitive resin composition of the present invention are the above-mentioned alkylsulfonium salt compounds, polymer compounds and solvents, but if necessary, surfactants, dyes and stabilizers Other components such as a coating improver and a dye may be added.

As a developer for forming a fine pattern using the present invention, an appropriate organic solvent or a mixed solvent thereof or an appropriate solvent depending on the solubility of the polymer compound used in the present invention is used. An alkaline aqueous solution having a concentration or a mixture thereof with an organic solvent may be selected. Further, other components such as a surfactant may be added to the developer as needed. Examples of the organic solvent used include acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol, tetrahydrofuran, dioxane and the like. Examples of the alkaline solution used include inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium silicate, and ammonia, and organic alkalis such as ethylamine, propylamine, diethylamine, dipropylamine, trimethylamine, and triethylamine. Solutions containing amines, and organic ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylhydroxymethylammonium hydroxide, triethylhydroxymethylammonium hydroxide, and trimethylhydroxyethylammonium hydroxide, and aqueous solutions. However, the present invention is not limited to these.

[0041]

The operation of the present invention will be described. First, a coated film of the photosensitive resin composition of the present invention is formed, and exposed to far ultraviolet rays such as ArF excimer laser, the compound represented by the general formula (1) contained in the exposed portion of the coated film is An acid is generated according to the general formula (11).

[0042]

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(Wherein R ¹ , R ² and R ³ are as defined above. R
¹² , R ¹³ and R ¹⁴ are any of R ¹ , R ² and R ³ or residues related thereto. )

In the present invention, for example, a resin represented by the general formula (9) (where R ⁵ is a tetrahydropyran-2-yl group, R ⁶ is a hydrogen atom, and R ⁷ and R ⁸ are methyl groups) is used. At this time, the protonic acid generated by the light irradiation causes a chemical change of the tetrahydropyranyl group of the resin according to the reaction formula of the following formula (12) to generate a carboxylic acid group, 3,4-dihydro-2H-pyran, Induces significant changes in resist solubility.

[0045]

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When a heat treatment (PEB step) subsequent to the exposure is performed at a predetermined temperature, the deprotection group reaction occurs catalytically, and the sensitivity is amplified. The higher the processing temperature, the more the sensitivity is amplified. Since the resin whose functional group has been changed to a hydroxyl group by this reaction becomes alkali-soluble, the resin is melted by using an alkaline developer, and as a result, the exposed portion is melted to form a positive pattern.

As shown in the examples, it was confirmed that when the above alkylsulfonium salt was irradiated with an ArF excimer laser (wavelength: 193 nm), which was far ultraviolet light, protonic acid was generated.

Further, as shown in Examples, when the photosensitive resin composition of the present invention is used, a good rectangular fine pattern is formed with high sensitivity in a resolution experiment using, for example, an ArF excimer laser as exposure light. I was sure that.

That is, the photosensitive resin composition using the sulfonium salt compound having a bridged cyclic alkyl of the present invention as a photoacid generator can be used to form a fine pattern in lithography using far ultraviolet rays of 180 nm to 220 nm as exposure light. It can be used as a photo resist.

[0050]

EXAMPLES The present invention will be described in more detail with reference to Synthesis Examples, Examples and Reference Examples, but the present invention is not limited to these Examples.

(Synthesis Example 1) Synthesis of β-oxocyclohexylmethyl (2-norbornyl) sulfonium trifluoromethanesulfonate

[0052]

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The following synthesis operation was performed under a yellow lamp.

In an eggplant type flask (for 300 ml), 2
7.07 g of chlorocyclohexanone (0.053 mol
1) is dissolved in 50 ml of ethanol. Then, 25 ml of a 15% aqueous solution of methyl mercaptan sodium salt was added dropwise using a dropping funnel, and the mixture was stirred at room temperature for 3 hours. The reaction mixture is poured into 300 ml of water, and the organic layer is extracted with methylene chloride. After drying over magnesium sulfate, methylene chloride is distilled off. This was distilled under reduced pressure to obtain 6.0 g of methylmercapto-2-chlorocyclohexanone (bp 46.5-47.5 ° C / 0.3 mmHg, yield 78%).

Next, in an eggplant-shaped flask (for 300 ml), 1 g of methyl mercapto-2-cyclohexanone was added.
(0.0078 mol) was dissolved in 5 ml of nitromethane and stirred with a Teflon stirrer / magnetic stirrer. There 10 g of 2-bromonorbornane (0.05 g)
7 mmol) using a dropping funnel.
Stirred for hours. Next, silver trifluoromethanesulfonate 2
g (0.0078 mol) dissolved in 100 ml of nitromethane was gradually added dropwise using a dropping funnel. After stirring for 3 hours, the precipitated silver bromide was filtered off, and the nitromethane solution was concentrated to 20 ml. And put it in diethyl ether 30
Add in 0 ml. After washing the precipitated crystals several times with diethyl ether, the operation of dissolving the residue in acetone and reprecipitating in ether is repeated three times to obtain white crystals.
15 g was obtained (38% yield). The target structure is ¹ H-NM
R measurement (AMX-400 type NMR apparatus manufactured by Bruker),
It was confirmed by IR measurement (IR-470 manufactured by Shimadzu Corporation), elemental analysis and the like.

Melting point: 111-113 ° C. Decomposition starting temperature: 152 ° C. ¹ H-NMR (CDCl ₃ , internal standard substance: tetramethylsilane): δ (ppm) 1.35-2.28 (m, 16)
H) 2.30-3.09 (m, 5H), 3.67-
3.78 (m, 1H), 4.95-5.31 (m, 1
H) IR (KBr tablet, cm ^-1 ) 3020, 2940 (ν
_CH ), 1746 (ν _{C = O} ), 1420 (ν _CH ), 1
260 (ν _CF ), 1160, 1032 (ν _{S = O} ) Elemental analysis C H S actual value (% by weight) 46.55 5.60 16.42 Theoretical value (% by weight) 46.62 5.48 16.59 (However, the theoretical value is C ₁₅ H ₂₁ O ₄ F ₃ S ₂ (MW 38
Calculated value for 6.44))

Synthesis Example 2 Cyclohexylmethyl (β-
Synthesis of oxonorbornyl) sulfonium trifluoromethanesulfonate

[0058]

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The following synthesis operation was carried out under a yellow lamp.

An eggplant type flask with a reflux condenser (300 m
8.03 g of cyclohexyl mercaptan
(0.069 mol), 2.8 g of sodium hydroxide
(0.07 mol) and 80 ml of ethanol are heated to reflux. When all the sodium hydroxide has dissolved, cool to room temperature. There 10 g of 3-chloronorbornanone (0.
(069 mol) using a dropping funnel, and further stirred at 50 ° C. room temperature for 1 hour. 300 m of water in the reaction mixture
and extract the organic layer with methylene chloride. After drying over magnesium sulfate, methylene chloride is distilled off. 2. Cyclohexylmercapto-β-oxonorbornane was subjected to column separation using methylene chloride as a developing solvent.
8 g was obtained (35% yield).

Next, in an eggplant type flask (for 300 ml), 2.0 g (0.0093 mol) of cyclohexylmercapto-β-oxonorbornane was added to 15 ml of nitromethane.
The mixture was dissolved in the resulting solution and stirred with a Teflon stirrer / magnetic stirrer. 13.2 g of methyl iodide (0.
093 mol) was added using a dropping funnel, and after the addition, the mixture was stirred at room temperature for 3 hours. Next, 2.39 g (0.0093 mol) of silver trifluoromethanesulfonate was added to nitromethane 10
A solution dissolved in 0 ml was gradually dropped using a dropping funnel. After stirring for 3 hours, the precipitated silver iodide was separated by filtration and the nitromethane solution was concentrated to 20 ml. It is added in 200 ml of diethyl ether. After washing the precipitated crystals several times with diethyl ether, the operation of dissolving the residue in acetone and reprecipitating in ether was repeated three times to obtain 1.28 g of white crystals (36% yield). The structure of the target substance was measured by ¹ H-NMR measurement (AMX-400 type NMR apparatus manufactured by Bruker) and IR measurement (IR-47 manufactured by Shimadzu Corporation).
0), and confirmed by elemental analysis and the like.

Melting point: 110-113 ° C. Decomposition starting temperature: 151 ° C. ¹ H-NMR (CDCl ₃ , internal standard substance: tetramethylsilane): δ (ppm) 1.35-2.28 (m, 1
7H), 2.30-3.09 (m, 4H), 3.67-
3.78 (m, 1H), 4.95-5.31 (m, 1
H) IR (KBr tablet, cm ^-1 ) 3020, 2940 (ν
_CH ), 1746 (ν _{C = O} ), 1420 (ν _CH ), 1
260 (ν _CF ), 1160, 1032 (ν _{S = O} ) Elemental analysis CH S observed (wt%) 46.41 5.71 6.22 theoretical (wt%) 46.62 5.48 16.59 (However, the theoretical value is C ₁₅ H ₂₁ O ₄ F ₃ S ₂ (MW 38
Calculated value for 6.44))

(Synthesis Example 3) Synthesis of adamantylmethyl (β-oxocyclohexyl) sulfonium trifluoromethanesulfonate

[0064]

Embedded image

In the same manner as in Example 1, except that 10 g (0.057 mol) of 2-bromonorbornane was replaced by 12.13 g (0.057 mol) of 2-bromoadamantane to obtain 0.8 g (yield: 24%). ).

Melting point: 113-115 ° C. Decomposition starting temperature: 155 ° C. IR (cm ⁻¹ ) (KBr tablet) 3020, 2940 (ν
_CH ), 1746 (ν _{C = O} ), 1420 (ν _CH ), 1
260 (ν _CF ), 1160, 1032 (ν _{S = O} ) Elemental analysis CH S observed value (% by weight) 50.20 6.18 14.82 Theoretical value (% by weight) 50.45 6.36 14.94 (However, the theoretical value is C ₁₈ H ₂₇ O ₄ F ₃ S ₂ (MW 42
8.55)

Example 1 Measurement of transmittance of an alkylsulfonium salt-containing resin film Poly (methyl methacrylate) (manufactured by Aldrich Chemical Company, Inc., average molecular weight 12,000, 6 g of ethylcellosolve acetate, hereinafter referred to as PMMA) )
1.5 g and 0.075 g of the alkylsulfonium salt obtained in Synthesis Example 1 (the alkylsulfonium salt was 5% by weight based on PMMA) were dissolved, and the solution was further filtered through a membrane filter having a pore size of 0.2 μm. It was spin-coated on a quartz substrate and baked on a hot plate at 100 ° C. for 120 seconds. By this operation, a thin film having a thickness of about 1 μm was obtained. The wavelength dependence of the transmittance of the obtained film was measured using a UV-365 UV-visible spectrophotometer manufactured by Shimadzu Corporation.
The results are shown in FIG. As a comparative example, a measured spectrum under the same conditions when a known compound, triphenylsulfonium trifluoromethanesulfonate (hereinafter abbreviated as TPS) is used instead of the PMMA-only film and the alkylsulfonium salt is also shown.

From the results of this example, it was found that TPS-containing PMMA
In the film, the transmittance is extremely reduced in the wavelength region of 220 nm or less. However, the alkylsulfonium salt of Example 1, which is a component of the present invention, has a high transmittance, and these compounds have an exposure wavelength of 220 nm. It was shown to be effective as a material for the following chemically amplified resist for lithography.

(Example 2) ArF excimer laser light (1
PMMA film (thickness: 1.0 μm)
In m), the amount of photoacid generated and the efficiency of the alkylsulfonium salt compound obtained in Synthesis Example 1 were measured. A film similar to that of Example 1 is formed on a 3-inch silicon wafer,
The thin film was irradiated with ArF excimer laser (EX-700 manufactured by Lumonics) light having a center wavelength of 193.3 nm. At this time, the exposure amount is 40 mJ · cm ⁻² and the exposure area is 20 cm ² . After irradiation, the thin film was dissolved in acetonitrile, and the solution was added to an acetonitrile solution containing a sodium salt of tetrabromophenol blue, and the visible absorption spectrum was measured. [Quantification of the generated acid was determined by Analytical Chemistry 48]
Volume (No. 2), pages 450 to 451 (1976), and determined from the change in absorbance at 619 nm]. Generated acid amount is 3
0 nmol was confirmed to be a sufficient value for pattern resolution.

From the above results, it was shown that the alkylsulfonium salt compound obtained in Example 1 was effective as a photoacid generator.

(Example 3) In the same manner as in Example 2, except that the alkylsulfonium salt compound obtained in Synthesis Example 2 was used instead of the alkylsulfonium salt compound obtained in Synthesis Example 1, the photoacid generation amount and The efficiency was measured. As a result, it was confirmed that the amount of generated acid was 28 nmol, which was a sufficient value for pattern resolution.

From the above results, it was shown that the alkylsulfonium salt compound obtained in Example 2 was effective as a photoacid generator.

Example 4 In the same manner as in Example 2, except that the alkylsulfonium salt compound obtained in Example 3 was used in place of the alkylsulfonium salt compound obtained in Synthesis Example 1, the photoacid generation amount and The efficiency was measured. As a result, it was confirmed that the amount of generated acid was 25 nmol, which was a sufficient value for pattern resolution.

From the above results, it was shown that the alkylsulfonium salt compound obtained in Example 3 was effective as a photoacid generator.

(Example 5) ArF excimer laser contact exposure experiment using the photosensitive resin composition according to the present invention The following experiment was conducted under a yellow lamp.

A resist material having the following composition was prepared. (A) 2.97 g of poly (tricyclo [5.2.1.0 ^2,6 ] decanyl acrylate-co-tetrahydropyranyl methacrylate-co-methacrylic acid) (resin: polymer compound of Reference Example 2) ) Β-oxocyclohexylmethyl (2-norbornyl) sulfonium trifluoromethanesulfonate (photoacid generator: compound of Example 1) 0.03 g (c) 12.00 g of propylene glycol monomethyl ether acetate (solvent)

The above mixture was filtered using a 0.2 μm Teflon filter to prepare a resist. The pattern forming method will be described below (see FIG. 2). The above resist material is spin-coated on a 3-inch silicon substrate,
Baking was performed on a hot plate at 05 ° C. for 60 seconds to form a thin film having a thickness of 0.7 μm [FIG.
(A)]. At this time, the transmittance per 1 μm of film thickness was 73.2%, which was sufficiently high transparency as a single-layer resist. Next, as shown in FIG. 3, the formed wafer was allowed to stand in a simple exposure experiment machine sufficiently purged with nitrogen. A mask in which a pattern was drawn with chrome on a quartz plate was brought into close contact with the resist film, and ArF excimer laser light was irradiated through the mask [FIG. 2 (b)]. Immediately thereafter, bake on a hot plate at 120 ° C. for 40 seconds, develop with an alkaline developing solution (1.0% by weight aqueous solution of tetramethylammonium hydroxide) at a liquid temperature of 23 ° C. for 60 seconds, and then rinse with pure water for 60 seconds. I did each. As a result, only the exposed portion of the resist film was dissolved and removed in the developing solution, and a positive pattern was obtained [FIG.
(C)]. In this experiment, the exposure energy was 35 mJ
/ Cm ² , a resolution of 0.25 μm line and space was obtained.

Example 6 A resist material was prepared in the same manner as in Example 5 except that the alkylsulfonium salt compound of the present invention obtained in Synthesis Example 2 was used as an acid generator, and then a pattern was formed. A resolution of 0.25 μm line and space was obtained.

Example 7 A resist was prepared in the same manner as in Example 5 except that the alkylsulfonium salt compound of the present invention obtained in Synthesis Example 3 was used as an acid generator, and then a pattern was formed. A resolution of 0.25 μm line and space was obtained.

(Reference Example 1) As in Example 5, except that
Instead of the alkylsulfonium salt synthesized in Synthesis Example 1, 1
-Adamantyl dimethylsulfonium trifluoromethanesulfonate (literature DN Kevil, SW Anderson (DN Kevil and SW An)
derson), Journal of the American Chemical Society (Journal of the
he American Chemical Soci
ety), 108, 1599-1585, 19
1986) was used to measure the amount of acid generated. The proton acid generation amount was 1 nmol, and the efficiency was as low as 1/30 of the acid generation amount in the case of the compound of Example 1 under the same conditions.

From the comparison between Example 5 and this Reference Example, it was found that the structure of the ketone group (β-oxoalkyl group of the bridged cyclic hydrocarbon and the monocyclic hydrocarbon) in the alkylsulfonium compound was far ultraviolet light (in this case, ArF excimer laser light (193
It is evident that the photoacid generation according to (nm)) increases the efficiency.

Reference Example 2 Poly (tricyclo [5.2.
1.0 ^2,6 ] decanyl acrylate-co-tetrahydropyranyl methacrylate-co-methacrylic acid)

In a 300 ml eggplant type flask equipped with a three-way stopcock, dry tetrahydrofuran (TH
F) 14.0 g (0.068 mol) of tricyclo [5.2.1.0 ^2,6 ] decane acrylate and 6.8 g (0.04 mol) of tetrahydropyranyl methacrylate in 80 ml
mol), 0.52 g of methacrylic acid (0.006 mol)
l) was dissolved. There, AIBN (initiator) 0.91
8 g (0.015 mol) of a THF solution (30 ml) was added, and the mixture was heated at 60 to 65 ° C. for 1 hour. Thereafter, reprecipitation was performed twice by pouring into 500 ml of hexane. The deposited precipitate was collected by filtration and dried under reduced pressure overnight to obtain 8.5 g of a white powder. The ratio of the obtained tricyclodecanyl acrylate unit, tetrahydropyranyl methacrylate unit and methacrylic acid unit is 60:35:
It was 5. From GPC measurement, the average molecular weight was 43,000.
(In terms of polystyrene).

Reference Example 3 ArF Excimer Laser Contact Exposure Experiment Using the Photosensitive Resin Composition According to the Present Invention The following experiments were conducted under a yellow lamp.

A resist material having the following composition was prepared. (A) 2.85 g of poly (tricyclo [5.2.1.0 ^2,6 ] decanyl acrylate-co-tetrahydropyranyl methacrylate-co-methacrylic acid) (resin: polymer compound of Reference Example 2) ) Synthesis of 2-oxocyclohexyl [methyl (2-cyclohexyl) sulfonium trifluoromethanesulfonate] (photoacid generator) 0.15 g (c) Propylene glycol monomethyl ether acetate (solvent) 12.00 g

The above mixture was filtered using a 0.2 μm Teflon filter to prepare a resist. The pattern forming method will be described below (see FIG. 2). The above resist material is spin-coated on a 3-inch silicon substrate,
Baking was performed on a hot plate at 05 ° C. for 60 seconds to form a thin film having a thickness of 0.7 μm [FIG.
(A)]. At this time, the transmittance per 1 μm of film thickness was 70%, which was sufficiently high transparency as a single-layer resist. Next, as shown in FIG. 3, the formed wafer was allowed to stand in a simple exposure experiment machine sufficiently purged with nitrogen. A mask in which a pattern was drawn with chrome on a quartz plate was brought into close contact with the resist film, and ArF excimer laser light was irradiated through the mask [FIG. 2 (b)]. Immediately afterwards 105
Baking on a hot plate for 90 seconds at 23 ℃
Was developed for 60 seconds with an alkali developing solution (2.0% by weight of tetramethylammonium hydroxide aqueous solution), and then rinsed with pure water for 60 seconds.
As a result, the pattern could not be resolved.

[0087]

As apparent from the above description, the photosensitive resin composition containing the alkylsulfonium salt compound of the present invention has high transparency in the far ultraviolet region of 180 nm to 220 nm. In addition, it exhibits high sensitivity and resolution to exposure light of far ultraviolet light, and is useful as a photoresist using far ultraviolet light of 180 nm to 220 nm as exposure light. Furthermore, by using the photosensitive resin composition of the present invention,
It is possible to form a fine pattern necessary for manufacturing a semiconductor device.

[Brief description of the drawings]

FIG. 1 shows the results of ultraviolet-visible spectrophotometry of a compound obtained in Synthesis Example 1 or a PMMA film containing TPS, and a PMMA film.

FIG. 2 is a process cross-sectional view of a positive pattern forming method using a photosensitive resin composition according to the present invention.

FIG. 3 is a schematic view of a simple exposure experiment machine used in an exposure experiment shown in a fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Thin film of photosensitive resin composition 2a Resin pattern according to the present invention 3 Chromium material of pattern mask (light shielding portion) 4 Quartz plate portion of transmission pattern mask (transmission portion) 5 ArF excimer laser beam 6 Glove box 7 Homogenizer 8 Mask 9 Wafer 10 Nitrogen suction port 11 Nitrogen exhaust port, 12 XY stage

Claims (10)

[Claims] 1. A photoacid generator comprising a sulfonium salt compound having a bridged cyclic alkyl group in at least one of the substituents represented by the general formula (I), and a resin comprising: Resin composition. Embedded image (At least one of R ¹ and R ^{2 represents} an alkyl group having a bridged cyclic hydrocarbon group, the rest represents a linear, branched or monocyclic alkyl group, and R ³ represents an oxo group at the β-position. A monocyclic alkyl group or a bridged cyclic alkyl group having an oxo group at the β-position, and Y￣ represents a counter ion.) 2. A photoacid generator comprising a sulfonium salt compound having a bridged cyclic alkyl group as one of the substituents represented by the general formula (II), and a photosensitive resin comprising a resin Composition. Embedded image (At least one of R ¹ ′ and R ² ′ represents a monocyclic alkyl group, the rest represents a linear, branched or monocyclic alkyl group, and R ³ ′ is a bridged ring having an oxo group at the β-position. Represents a formula alkyl group, and Y represents a counter ion.) 3. A photosensitive resin composition comprising a photoacid generator comprising the sulfonium salt compound represented by the general formula (I) according to claim 1 and a resin (provided that the general formula (I) In I), at least one of R ¹ and R ² is an alkyl group having 7 to 12 carbon atoms having a bridged cyclic hydrocarbon group having 7 to 10 carbon atoms, and the rest is a linear chain having 1 to 8 carbon atoms; Represents a branched or monocyclic alkyl group,
R ³ represents a monocyclic alkyl group having an oxo group at the β-position or a bridged cyclic alkyl group having an oxo group at the β-position, and Y￣ represents a counter ion. ). 4. A photosensitive resin composition comprising a photoacid generator comprising a sulfonium salt compound represented by the general formula (II) according to claim 2 and a resin (provided that:
In the general formula (II), at least one of R ¹ ′ and R ² ′ is a monocyclic alkyl group having 5 to 7 carbon atoms, and the rest is a linear, branched or monocyclic alkyl group having 1 to 8 carbon atoms. , R ³ 'represents a bridged cyclic alkyl group having an oxo group at the β-position having 7 to 10 carbon atoms, and Y￣ represents a counter ion. ). 5. A photo-acid generator comprising a sulfonium salt compound having a bridged cyclic alkyl group represented by the general formula (III), and a photosensitive resin composition comprising a resin (However, in the general formula (III), Y￣ is a counter ion, R ¹ ″ is a norbornyl group,
An adamantyl group or β-oxonorbornane-2
-Yl group, R ² ″ is a methyl group, R ³ ″ is a β-oxocyclohexyl group or a cyclohexyl group). Embedded image 6. A counter ion represented by Y￣ is BF ₄ }, As
F ₆ ￣, SbF ₆ ￣, PF ₆ ￣ or CF ₃ SO ₃ ￣
A photosensitive resin composition comprising the photoacid generator according to any one of claims 1 to 5 and a resin. 7. A resin having a thickness of 180 nm in a thin film having a thickness of 1 μm.
7. The photosensitive resin composition according to claim 1, which is a polymer compound capable of transmitting 40% or more of light having a wavelength of about 220 nm. 8. The photosensitive resin composition according to claim 1, comprising 0.1 to 40 parts by weight of a photoacid generator and 60 to 99.9 parts by weight of a resin. 9. A thin film is formed on a substrate by using the photosensitive resin composition according to claim 1, exposed to light having a wavelength of 180 nm to 220 nm, and patterned by a developing process. Pattern forming method. 10. The pattern forming method according to claim 9, wherein the exposure light is ArF excimer laser light.