JP2776204B2 - Alkylsulfonium salt, photosensitive resin composition for deep ultraviolet exposure, and pattern forming method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel alkyl sulfo
The present invention relates to a lithium salt, a photosensitive resin composition and a pattern forming method using the same, and more specifically,
An alkylsulfonium salt, a photosensitive resin composition, and a pattern forming method using the same, which are preferably used when far ultraviolet rays having a wavelength of 220 nm or less 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, D with a degree of integration up to 64M
The manufacture of RAM (Dynamic Random Access Memory) requires a minimum pattern size of 0.35 μm line and space resolution. Until now, g-line (438 nm) and i-line (365 nm) of high-pressure mercury lamps have been used as light sources. It has been. 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 a finer processing technology, an excimer laser (KrF: 248 nm, KrCl: 222 nm, A
It is considered that the use of shorter wavelength light (deep UV light, far ultraviolet light) such as rF: 193 nm, F ₂ : 157 nm is effective (Takumi Ueno, Takao Iwayanagi, Saburo Nonogaki, Hiroshi Ito, C Grant Wilson,
"Short Wavelength Photoresist Materials-Microfabrication for ULSI-", Bunshin Publishing, 1988), now KrF
Lithography is 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
technology) B3, pages 306 to 309 (1
985) Wilkins
ns) 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, pp. 11-23 (19
1984)]. A photoacid generator is a substance that generates an acid upon irradiation with light. The characteristic of the chemically amplified resist is that the protonic acid generated by the photoacid generator as a component is moved within the resist solid phase by heat treatment after exposure, and the acid catalytically reacts with the chemical change of the resist resin etc. Amplification is several hundred times to several thousand times. 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, Journal of the Organic Chemistry (Journal).
of the Organic Chemistry) 4
Vol. 3, No. 15, pp. 3055-3058 (1978)
Described in J. et al. V. Crivello (JV Criv)
ello) et al., a triphenylsulfonium salt derivative,
2,6-Dinitrobenzyl esters [ T. X. Noona
(TX Neenan) et al., SPIE Procedure
(Proceedings of SPIE), 1
086, pp. 2-10 (1989)] , 1, 2 , 3-
Tri (methanesulfonyloxy) benzene [Takumi Ueno et al., Proceeding of PME '89 (Pr
receiveds of PME'89), Kodansha,
413-424 (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]

At present, a chemically amplified resist for KrF excimer laser exposure generally has a thickness of 1 μm.
Is 60% or more, and in a resist, the transmittance at the exposure wavelength is important for pattern resolution.

[0008] However, currently widely used g-line, i
When exposing a single-layer chemically amplified resist for X-ray or KrF excimer laser exposure with exposure light having a wavelength shorter than 220 nm, for example, ArF excimer laser (193 nm),
In general, the pattern cannot be resolved because the resist absorbs the exposure light so strongly. That is, 0.7 ~
Most of the light of a single-layer resist having a thickness of about 1.0 μm is absorbed in the vicinity of the surface on the side where the exposure light is incident, and the 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 expected to be a next-generation light source of rF, the existing resist does not resolve the pattern at all. The photoacid generators described above, including the triphenylsulfonium salt derivative of Krivero et al., Which is a component of the chemically amplified resist, all have an aromatic ring in their structure, so
Strongly absorbs light of nm or less. For this reason, the current photoacid generator can be expected to have higher resolution for the above-mentioned reasons.
It cannot be used for a chemically amplified resist using light having a wavelength of 0 nm or less as exposure light.

[0009] Similarly, the same problems as those of the photoacid generator also occur with respect to the base polymer compound in the resist.
Novolak resin, which is a polymer compound used for most of the current i-line resists, or poly (p-vinylphenol), which is currently frequently used as a base polymer for chemically amplified resists for KrF excimer laser exposure, is used. It has an aromatic ring in its molecular structure. This is because in order for the resist resin to exhibit sufficient resistance to the dry etching step, which is a process after pattern formation in the semiconductor manufacturing process, it is necessary to include many unsaturated bonds, which are strong bonds, in the molecular structure of the resin. It is. For this reason, aromatic rings have been used in resist polymer compounds as an indispensable structure that sufficiently satisfies the purpose. As mentioned earlier, the required dimensions for microfabrication have become smaller, and KrF resists for light sources with wavelengths shorter than the i-line, which are being actively studied, are now being replaced by polystyrene instead of novolak resins having strong absorption at 248 nm. (P-vinylphenol) has come to be frequently used. However, this resin is a KrF excimer laser (248
nm) (transparency is about 70% when the film thickness is 1 μm), but has strong absorption in a shorter wavelength region because the structure contains an aromatic ring. Therefore, for the same reason as described above, it cannot be used for a resist for lithography using light having a wavelength shorter than KrF, specifically, light having a wavelength of 220 nm or less, as exposure light. Examples of the resin that is transparent in a wavelength region of 220 nm or less include a methacrylic resin such as poly (methyl methacrylate). By removing the aromatic ring from the resin structure in this way, a polymer compound that is transparent to light of 220 nm or less can be obtained, but the property that can withstand the above-mentioned dry etching process is not obtained, and as a result, it is also used as a resist. Is not available. As an attempt to solve this problem, a resist using an alicyclic polymer has been reported. [Takechi et al., Journal of Photopolymer Science and Technology (Journal of Phototop)
oligomer Science and Techno
5) (No. 3), pp. 439-446 (19)
1992)]. That is, a copolymer of poly (adamantyl methacrylate) and poly (tert-butyl methacrylate), which are alicyclic polymers, has been proposed as a polymer compound having transparency to 193 nm and resistance to dry etching.

As described above, although there are few reports on the number of polymer compounds for lithography at a wavelength of 220 nm or less, there are reports, but it is essential to improve 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.

One of the current technical challenges in this field is:
Develop a chemically amplified resist material using a photoacid generator that has high transparency to far ultraviolet light of 220 nm or less and high photoreaction efficiency (photoacid generation efficiency), and forms a pattern using it. Is to develop a method.

[0012]

SUMMARY OF THE INVENTION The inventors have result of intensive studies, the technical problem, alkyl sulfonium salt compound of the structures disclosed in the following and the photosensitive resin composition and photosensitive resin it with the ingredients The present invention was found to be solved by performing patterning by light irradiation using the composition, and reached the present invention.

The alkylsulfonium salt compound of the present invention is represented by the following general formula (I).

[0014]

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However, in the general formula (I), at least one of R ¹ and R ² is a cyclic group having 5 to 7 carbon atoms.
An alkyl group (more specifically, a cyclopentyl group,
Rohexyl, cycloheptyl, cyclopropylmethyl
Group, 4-methylcyclohexyl group or cyclohexyl
And the other is a linear or branched alkyl group having 1 to 8 carbon atoms ( more specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-
Butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, etc.)
Alternatively , it represents a cyclic alkyl group having 5 to 7 carbon atoms .

R ³ is a 2-oxo cyclic group having 5 to 7 carbon atoms
An alkyl group (more specifically, R ³ is 2-oxocyclo
Pentyl group, 2-oxocyclohexyl group or 2-
Oxocycloheptyl group, etc.)
2-oxo linear or branched alkyl group of chair 8
(More specifically, a 2-methyl-2-oxoethyl group,
2-ethyl-2-oxoethyl group, 2-isopropyl-
2-oxoethyl group or 2-hexyl-2-oxo
Ethyl group) is preferably used.

Particularly excellent thermal stability as a photoacid generator
(High decomposition start temperature) and high melting point
In view of this, at least one of R ¹ and R ² is a cyclic
It must be a alkyl group.

[0018] Y ^- as a counter ion represented by the, BF ₄
^- (Tetrafluoroborate ion), AsF
₆ ^- (hexafluoroarsenate ion), SbF
₆ ^- (hexafluoroantimonate ion), PF
₆ ^- (hexafluorophosphate ion), CF ₃ S
O ₃ ^- (trifluoromethanesulfonate ion),
Cl ^- (chlorine ions), Br ^- (bromine ion) or I ^- (iodide ion), CH ₃ SO ₃ ^- (methanesulfonate ion), and the like. From the viewpoint of suppressing impurity ion contamination in the integrated circuit manufacturing process or suppressing scattering and disappearance of protonic acid from the resist in post-exposure bake heat treatment applied in the resist pattern forming step. Of the counterions, BF ₄
^- (Tetrafluoroborate ion), AsF
₆ ^- (hexafluoroarsenate ion), SbF
₆ ^- (hexafluoroantimonate ion), PF
₆ ^- (hexafluorophosphate ion), CF ₃
SO ₃ ^- (trifluoromethanesulfonate ion)
Is more preferred.

The alkylsulfonium salt derivative of the present invention can be obtained, for example, from the Journal of the American Chemical Society (Journal of the A).
merchandise Chemical Society)
108 (No. 7), pp. 1579-1585 (1986
) On the sulfonium salts listed in
It can be produced by applying the method of DN Kevil et al. That is, the general formula (II) or (I
In a nitromethane solution of a sulfide derivative represented by II), for example, an alkyl halide represented by the general formula (IV) or (V) is added in an excess amount [2 to 100 times mol (more preferably 5 to 20 times) with respect to the sulfide derivative] Mol)]
In addition, 0.5-5 hours at room temperature (preferably 1-2 hours)
react. Thereafter, a solution prepared by dissolving an organic acid metal salt represented by the general formula (VI) in nitromethane in an equimolar amount with respect to the sulfide derivative is added.
To 24 hours. Thereafter, the insoluble metal salt is filtered off, and the filtrate is concentrated, and then poured into a large amount of a poor solvent such as diethyl ether to be reprecipitated. The resulting precipitate is recrystallized from a suitable solvent (such as ethylcellosolve acetate) to obtain the desired alkylsulfonium salt derivative [general formula (I)].

R ³ -SR ¹ (II) (wherein R ¹ and R ³ are the same as above) R ³ -SR ² (III) (where R ² and R ³ are the same as above) R ^2- W (IV) (wherein R ² is the same as above, W is a halogen atom such as iodine and bromine) R ¹ -W (V) (where R ¹ and W are the same as above) M ⁺ Y ⁻ ( VI) (wherein M ⁺ is K ⁺ , Na ⁺ , or Ag ⁺ , Y ⁻ is the same as above) A photoacid generator developed for KrF excimer laser lithography [triphenylsulfonium described in Krivero et al. Trifluoromethanesulfonate (hereinafter TP
S) is extremely intense in the deep ultraviolet region of 220 nm or less and cannot be used as a component of a resist for ArF excimer laser lithography. When compared with this TPS, each of the above sulfonium salt derivatives described in the present invention is 185.5 to 220 n.
The light absorption in the far ultraviolet region of m is remarkably low, and it is clear that it can be used as a component of a resist for ArF excimer laser lithography in terms of transparency to exposure light.

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

In the photosensitive resin composition of the present invention characterized by containing the alkylsulfonium salt represented by the general formula (I), the alkylsulfonium salt compound represented by the general formula (I) may be used alone. It is used, but two or more kinds may be used as a mixture. In the photosensitive resin composition of the present invention, the content of the alkylsulfonium salt compound represented by the general formula (I) is usually 0.1 to 40 parts by weight based on 100 parts by weight of the total solid content including itself. , Preferably 1 to 25 parts by weight. This content is 0.
If the amount is less than 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.

The high molecular compound which is a component of the present invention includes:
A polymer having high transparency in the deep ultraviolet region of 220 nm or less and 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 (VII) can be used.

[0024]

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[In the above formula, n is 5 to 1000
A positive integer of (more preferably 10 to 200), R ⁴
Represents a tricyclodecanyl group, a dicyclopentenyl group, a dicyclopentenyloxyethyl group, as shown in Table 1,
A cyclohexyl group, a norbornyl group or an adamantyl group, R ⁵ is a tert-butyl group, a methyl group, an ethyl group,
A propyl group, a tetrahydropyranyl group or a 3-oxocyclohexyl group, and x represents 0.1 to 1 (more preferably 0.2 to 0.7). ]

[0026]

[Table 1]

Further, a high molecular compound mixture containing a plurality of the above formula (VII) as a constituent element can also be used.

A preferred solvent used in the present invention is an organic solvent in which a component comprising a polymer compound and an alkylsulfonium salt is sufficiently dissolved, and the solution is capable of forming a uniform coating film by a spin coating method. 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" constituent components 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, a dye, and a crosslinking agent may be added.

In the case where a fine pattern is formed by 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 solution or an alkaline aqueous solution having a concentration may be selected. As the organic solvent used, acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol,
Examples include tetrahydrofuran and dioxane. 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 or aqueous solutions containing amines, and organic ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylhydroxymethylammonium hydroxide, triethylhydroxymethylammonium hydroxide, and trimethylhydroxyethylammonium hydroxide are included. However, the present invention is not limited to these.

[0031]

The operation of the present invention will be described. First, a coating 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 specified by the general formula (I) contained in the exposed portion of the coating film is formed as follows: Generates an acid according to formula (VIII).

[0032]

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(In the formula, R ¹ , R ² and R ³ are the same as above.) In the present invention, for example, when a resin represented by the formula (VII) (where R ⁵ is a tert-butyl group) is used, The protonic acid generated by irradiation has the following formula (IX)
Causes a chemical change of the tert-butyloxy group of the resin to generate a carboxylic acid group and 2-butene, and eventually induces a change in the solubility of the resist.

[0034]

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When a heat treatment (post-exposure bake) subsequent to the exposure is performed at a predetermined temperature, the deprotection group reaction occurs catalytically, and 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-mentioned alkylsulfonium salt was irradiated with an ArF excimer laser (wavelength: 193 nm), which was far ultraviolet light, protonic acid was generated.

Further, when the photosensitive resin composition of the present invention is used as shown in the realization example, 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 containing the alkylsulfonium salt derivative obtained in the present invention as a constituent can be used as a photoresist for forming a fine pattern in lithography using far ultraviolet rays of 220 nm or less as exposure light.

[0039]

Next, the present invention will be described in more detail with reference to examples and reference examples, but the present invention is not limited to these examples.

Example 1 Synthesis of cyclohexylmethyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate

[0041]

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The following synthesis operation was performed under a yellow lamp.

In an eggplant type flask (for 300 ml), 2
-(Cyclohexylmercapto) cyclohexanone 1
0.0 g (41.1 mmol) of nitromethane 30 ml
And stirred with a Teflon stirrer / magnetic stirrer. 54 g of methyl iodide (380 mmo
l) was added using a dropping funnel, and after the addition, the mixture was stirred at room temperature for 1 hour. Next, 12.1 g of silver trifluoromethanesulfonate
(41.1 mmol) dissolved in 200 ml of nitromethane was gradually added dropwise using a dropping funnel. After stirring for 15 hours, the precipitated silver iodide was filtered off, and the nitromethane solution was concentrated to 20 ml. Diethyl ether 20
Added in 0 ml. After the precipitated crystals were washed several times with diethyl ether, the residue was reconstituted from ethyl cellosolve acetate to obtain 11.2 g of the desired product (63% yield).
Obtained. The structure of the target compound was measured by ¹ H-NMR measurement (Vulker-
AMX-400 NMR apparatus manufactured by Shimadzu Corporation, IR measurement (IR-470 manufactured by Shimadzu Corporation), elemental analysis and the like. Melting point: 91-93 ° C. ¹ H-NMR (CDCl ₃ , internal standard: tetramethylsilane): δ (ppm) 1.22-1.35 (m, 1
H), 1.40-1.78 (m, 6H), 1.84-
2.27 (m, 8H), 2.54-2.64 (m, 2
H) 2.70-2.80 (m, 1H), 2.81
(S, 1.5H), 2.92 (s, 1.5H), 3.6
2 (tt, 0.5H), 3.73 (tt, 0.5),
5.17 (t, 0.5H), 5.18 (t, 0.5H) IR (KBr tablet, cm ^-1 ) 2950, 2870 (v
_C-H ), 1710 (vC _{= O} ) 1450
(Ν _{C -H} ), 1276, 1256 (ν _{C -F} ), 11
48, 1034 (ν _{SO 3} ) Elemental analysis C H S actual value (% by weight) 44.43 6.38 16.84 Theoretical value (% by weight) 44.67 6.16 17.03 (However, the theoretical value is C ₁₄ H _{2 3} O ₄ S ₂ F ₃ (MW3
Calculation value for 78.4485) Decomposition onset temperature: 142 ° C (Example 2) Synthesis of dicyclohexyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate

[0044]

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Synthesized in the same manner as in Example 1 except that cyclohexyl iodide was used instead of methyl iodide (yield: 16%). Melting point: 172-174 ° C. ¹ H-NMR (CDCl ₃ , internal standard substance: Tetramethylsilane): δ (ppm) 0.97-2.3 (m, 24
H) 2.33-2.80 (m, 4H), 3.97-
4.47 (m, 2H), 5.20-5.35 (m, 1
H) IR (KBr tablet, cm ^-1 ) 2932, 2860,
(Ν _{C -H} ), 1700 (ν _{C = O} ) 1444 (ν
_C-H ), 1276, 1256 (vC- _F ), 116
8, 1050 (ν _{SO 3} ) Elemental analysis C H S actual value (% by weight) 51.58 6.75 14.74 Theoretical value (% by weight) 51.33 7.03 14.42 (However, the theoretical value is C ₁₉ H _{3 1} O ₄ S ₂ F ₃ (MW4
Calculation value for 44.5667) Decomposition onset temperature: 185 ° C (Example 3) Synthesis of cyclopentylmethyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate

[0046]

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The procedure of Example 1 was repeated, except that 2- (cyclohexylmercapto) cyclohexanone was replaced with 2
It was synthesized using-(cyclopentylmercapto) cyclohexanone (yield 93%, oil). ¹ H-NMR (CDCl ₃ , internal standard: tetramethylsilane): δ (ppm) 1.50-2.50 (m, 1
4H), 2.51-2.80 (m, 2H), 2.85
(S, 1.5H), 2.95 (s, 1.5H), 3.6
7-4.23 (m, 1H), 4.87-5.37 (m, 1H)
1H) IR (KBr tablet, cm ^-1 ) 2950, 2880 (ν
_C-H ), 1710 (ν _{C = O} ), 1448, 1424
(Ν _{C -H} ), 1264 (ν _{C -F} ), 1156,10
30 (ν _{SO 3} ) (However, theoretical value _{C 1 3 H 2 1 O 4} S 2 F 3 (MW3
(Calculated value for 62.4217)) (Example 4) Synthesis of cycloheptylmethyl (2-oxocyclopentyl) sulfonium trifluoromethanesulfonate

[0048]

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As in Example 1, except that 2- (cyclohexylmercapto) cyclohexanone was used instead of 2- (cyclohexylmercapto) cyclohexanone.
- was synthesized using (cycloheptyl mercapto) cyclopentanone (20% yield) mp: 97-99 ° C. (provided that the theoretical value is _{C 14 H 23 O 4 S 2} F 3 (MW3
76.4485)

[0050]

[0051]

[0052]

[0053]

[0054]

Example 5 Measurement of Transmittance of Alkyl Sulfonium Salt-Containing Resin Film The following film forming operation and resolution experiment were performed under a yellow lamp. 1.5 g of poly (methyl methacrylate) (manufactured by Aldrich Chemical Company, having an average molecular weight of 12,000, hereinafter abbreviated as PMMA) was added to 6 g of ethylcellosolve acetate and the alkylsulfonium salt obtained in Examples 1 to 4 together with 1.5 g of poly (methyl methacrylate). After dissolving 0.079 g, the solution was filtered through a membrane filter having a pore size of 0.2 μm. The obtained filtrate was spin-coated on a 3-inch quartz substrate, and baked at 100 ° C. for 120 seconds on a hot plate. 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
Although the transmittance in a wavelength 220nm or less area in film is extremely decreased, to Examples 1 a containing component of the present invention 4
The alkylsulfonium salts of (1) and (2) maintain high transmittance, indicating that these compounds are effective as a material for a chemically amplified resist for lithography having an exposure wavelength of 220 nm or less.

Example 6 The amount of photoacid generated and the efficiency of a PMMA film (film thickness: 1.0 μm) containing an alkylsulfonium salt when irradiated with ArF excimer laser light (193 nm) were measured.
The photoacid generator used is the compound shown in Examples 1 to 4 . The alkylsulfonium salt was contained at 5% by weight based on PMMA. Example on 3 inch silicon wafer
5 and forming a similar film, the center wavelength of 193.3 nm A
The thin film was irradiated with an rF excimer laser (EX-700 manufactured by Lumonix). At this time, the exposure amount is 40 mJ · c.
m ⁻² and the exposure area is 20 cm ² . After irradiation, the thin film was dissolved in acetonitrile, the solution was added to an acetonitrile solution containing sodium salt of tetrabromophenol blue, and the visible absorption spectrum was measured. [Quantification of the generated acid was determined by Analytical Chemistry (Analytical).
al Chemistry), Vol. 48 (No. 2), pages 450 to 451 (1976), and was determined from the change in absorbance at 619 nm]. Table 2 shows the results.

[0058]

[Table 2]

From the above results, it was shown that the alkylsulfonium salt which is a component of the present invention is effective as a photoacid generator. Furthermore, it is clear that the ketone group (2-oxocycloalkyl group) structure in the alkylsulfonium salt compound enhances the photoacid generation efficiency by far ultraviolet light (in this case, ArF excimer laser light).

Reference Example 1 Poly (tricyclodecanyl methacrylate-tert-)
Synthesis of butyl methacrylate 21.80 g of tricyclodecanyl methacrylate (0.
10 mol) and tert-butyl methacrylate 8.8.
In a 120 g toluene solution of 0 g (0.05 mol), 0.48 g (0.003 m) of azoisobutyronitrile was added.
ol) was dissolved in 10 ml of a toluene solution. Thereafter, a polymerization reaction was performed at 70 ° C. for 1 hour. After returning the reaction solution to room temperature, it was poured into 1 liter of methanol and washed.
The precipitate was collected by suction filtration. After repeating this washing operation three times, the product was dried under reduced pressure to obtain poly (tricyclodecanyl methacrylate-tert-butyl methacrylate) 1
4.52 g was obtained as a white powder (48.4% yield).
The obtained tricyclodecanyl methacrylate unit and te
The ratio of rt-butyl methacrylate units was 65:35. This copolymerization ratio was determined by ¹ H-NMR measurement. From GPC measurement, the average molecular weight was 53,000 (in terms of polystyrene).

(Example 7) ArF 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) poly ( tricyclodecanyl methacrylate -tert-butyl methacrylate) (resin: polymer compound of Reference Example 1 ) 2.85 g (b) cyclohexylmethyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate (Photoacid generator: compound of Example 1) 0.15 g (c) Cyclohexanone (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 resist material was spin-coated on a 3-inch silicon substrate and baked on a hot plate at 90 ° C. for 60 seconds to form a thin film having a thickness of 0.7 μm (FIG. 2A). At this time, the transmittance per 1 μm of film thickness was 73.2%, which was sufficiently high 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 with a pattern drawn with chrome on a quartz plate is stuck on the resist film,
ArF excimer laser light was irradiated through the mask [FIG. 2 (b)]. Immediately thereafter, it is baked on a hot plate at 100 ° C. for 90 seconds, developed with an alkali developing solution (2.0% by weight of tetramethylammonium hydroxide aqueous solution) at a liquid temperature of 23 ° C. for 60 seconds, and subsequently rinsed 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. 2 (c)]. In this experiment, when the exposure energy was about 68.5 mJ / cm ² , the value was set at 0.
A resolution of 25 μm line and space was obtained.

Examples 8 to 10 The same procedures as in Example 1 except that the alkylsulfonium salt compound of the present invention obtained in Examples 2 to 4 and 1-adamantyldimethylsulfonium trifluoromethanesulfonate were used as acid generators, respectively. A resist material was prepared in the same manner, and a pattern was formed in the same manner as in Example 7 . Table 3 shows the experimental conditions and results.

Based on the acid generation efficiency (the amount of acid generation at the same exposure amount) shown in Example 6 , the content of the photoacid generator in the resist was set to an amount that could sufficiently resolve the pattern. That is, the photoacid generator having a low photoacid generation efficiency was used in a larger amount than the others.

[0065]

[Table 3] *) 1-adamantyl dimethylsulfonium trifluoromethanesulfonate: Reference (DNKevill and S.
W. Anderson, J. Am. Chem. Soc., 108, 1579-1585 (19
86)).

[0066]

Embedded image

[0067]

As is apparent from the above description, the photosensitive resin composition containing the alkylsulfonium salt of the present invention has high transparency in the deep ultraviolet region of 220 nm or less, and It exhibits high sensitivity and resolution to exposure light of far ultraviolet rays, and is useful as a photoresist using far ultraviolet rays of 220 nm or less as exposure light. Further, 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 compounds obtained in Examples 1 and 2 , or TPS
1 shows the results of UV-visible spectrophotometry of a PMMA film containing, and a PMMA film.

FIG. 2 is a cross-sectional view showing steps 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 for an exposure experiment shown in Example 9.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 thin film of photosensitive resin composition 3 chrome material of pattern mask (light shielding portion) 4 quartz plate portion of pattern mask (transmission portion) 5 ArF excimer laser beam 6 glove box 7 homogenizer 8 mask 9 wafer 10 nitrogen inlet 11 Nitrogen exhaust port 12 XY stage 2a Resin pattern according to the present invention

Continuation of the front page (72) Inventor Etsuo Hasegawa 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-5-213861 (JP, A) JP-A-3-95556 ( JP, A) JP-A-3-148257 (JP, A) JP-A-64-35433 (JP, A) JP-A-5-222257 (JP, A) JP-A-7-25846 (JP, A) Tetrahedron ( 1973), Vol. 29, No. 14, p. 2065-2076 Bull. Chem. Soc. Jap. (1971), Vol. 44, no. 11, p. 3155-3158 Chemical Abstracts (1971), Vol. 71, 12542u, Angew. Chem. (1981), Vol. 93, no. 10, p. 933-934 J.C. Org. Chem. (1970), Vol. 35, No. 8, p. 2532-2358 J.P. Chem. Soc. , Chem. Commun. (1974), No. 22, p. 919-920 J.C. Chem. Soc. , Perkin Trans. 2 (1980), No. 6, p. 931-936 (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 381/12 CA (STN) REGISTRY (STN)

Claims (6)

(57) [Claims] 1. An alkylsulfonium salt represented by the following general formula (I). Embedded image (However, at least one of R ¹ and R ² is cyclic
An alkyl group, the other is a linear, branched or cyclic alkyl group, R ³ is a 2-oxo cyclic alkyl group or a 2-oxo linear or branched alkyl group, and Y ⁻ is a counter ion. Represents ) ^{2. At} least one of R ¹ and R ² is charcoal.
A cyclic alkyl group having a prime number of 5 to 7, and the other is a linear, branched, or C 5 to C 7 -C 8 alkyl group.
And R ³ is a 2-oxo cyclic alkyl group having 5 to 7 carbon atoms, or a 2-oxo cyclic alkyl group having 3 to 8 carbon atoms.
The alkylsulfonium salt according to claim 1, which is an oxo linear or branched alkyl group. 3. The counter ion represented by Y ⁻ is BF ₄ ⁻ , AsF
_{^{6 -, SbF 6 -, PF}} 6 - or CF ₃ SO ₃ ^- alkyl sulfonium salt according to claim 1 or 2 wherein the. 4. The method according to claim 1, wherein
Photosensitivity characterized by containing a killsulfonium salt
Resin composition. 5. A pattern comprising: forming a thin film on a substrate using the photosensitive resin composition according to claim 4 ; and performing patterning through exposure and development with light having a wavelength of 220 nm or less. Forming method. 6. The pattern forming method according to claim 5, wherein the exposure light is ArF excimer laser light.