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Resist composition for forming a pattern and method of forming a pattern wherein the composition 4-phenylpyridine as an additive - Kabushiki Kaisha Toshiba
Resist composition for forming a pattern and method of forming a pattern wherein the composition 4-phenylpyridine as an additive
United States Patent 5744281
A resist composition for forming a pattern, which comprises (a) a compound represented by the following formula (1) and satisfying the following inequalities, ##STR1## wherein R1 is hydrogen atom or methyl group, R2 is a monovalent organic group, m is 0 or a positive integer, n is a positive integer, and m and n satisfying a condition of 0.03≤n/(m+n)≤1, (b) a compound capable of generating an acid when irradiated with light, and (c) 4-phenylpyridine, wherein a weight-average molecular weight, Mw and a number-average molecular weight, Mn satisfy the following inequality, 4,000≤Mw≤50,000, 1.10≤Mw/Mn≤2.50 (Mw and Mn respectively represent value converted in styrene).
Niki, Hirokazu (Yokohama, JP)
Wakabayashi, Hiromitsu (Yokohama, JP)
Hayase, Rumiko (Yokohama, JP)
Oyasato, Naohiko (Kawaguchi, JP)
Sato, Kazuo (Yokohama, JP)
Chiba, Kenji (Yokohama, JP)
Hayashi, Takao (Tokyo, JP)
08/848747
430/176, 430/179, 430/191, 430/910
G03F7/004; G03F7/039; (IPC1-7): G03F7/039; G03F7/004A
430/270.1, 430/176, 430/179, 430/191, 430/910
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5679495 Radiation sensitive resin composition 1997-10-21 Yamachika et al. 430/270.1
5658706 Resist composition for forming a pattern comprising a pyridinium compound as an additive 1997-08-19 Niki et al. 430/270.1
5580695 Chemically amplified resist 1996-12-03 Murata et al. 430/270.1
5556734 Radiation sensitive resin composition comprising copolymer of isopropenylphenol and T-butyl(meth)acrylate 1996-09-17 Yamachika et al. 430/270.1
5403695 Resist for forming patterns comprising an acid generating compound and a polymer having acid decomposable groups 1995-04-04 Hayase et al. 430/192
5130392 Radiation-sensitive polymers 1992-07-14 Schwalm et al. 430/270.1
5100768 Photosensitive composition 1992-03-31 Niki et al. 430/270.1
4491628 Positive- and negative-working resist compositions with acid generating photoinitiator and polymer with acid labile groups pendant from polymer backbone 1985-01-01 Ito et al. 430/270.1
This application is a continuation-in-part of application Ser. No. 08/781,512 filed Jan. 9, 1997, now abandoned; which was a continuation of application Ser. No. 08/302,319 filed Sep. 8, 1994, now U.S. Pat. No. 5,658,706.
1. A resist composition for forming a pattern, which comprises:
(a) a compound represented by the following formula (1) and satisfying the following inequalities; ##STR17## wherein R1 is hydrogen atom or methyl group, R2 is a monovalent organic group, m is 0 or a positive integer, n is a positive integer, and m and n satisfying a condition of 0.03≤n/(m+n)≤1; 4. 000≤Mw≤50,000
1.10≤Mw/Mn≤2.50
wherein Mw and Mn respectively represent a weight-average molecular weight and number-average molecular weight as they are converted in styrene;
(c) 4-phenylpyridine.
2. The resist composition for forming a pattern according to claim 1, which further comprises (d) an alkali-soluble polymer.
3. The resist composition for forming a pattern according to claim 2, wherein a content of the component (b) is in the range of from 0.01% by weight to 30% by weight based on a total amount of the component (a) and the component (d).
4. The resist composition for forming a pattern according to claim 1, wherein a content of the component (c) is in the range of from 2 mole % to 60 mole % based on the number of mole calculated from the content of the component (b).
5. The resist composition according to claim 1, wherein said component (a) is a compound represented by the following formula (2): ##STR18## wherein p and q are numbers satisfying a condition of 0.10≤q/(p+q)≤0.60.
6. The resist composition for forming a pattern according to claim 1, wherein a content of the component (b) is in the range of from 0.01% by weight to 30% by weight based on an amount of the component (a).
In the processing of this pattern exposure, a reduced projection type exposure apparatus of a step-and-repeat system, which is generally called as a stepper is widely used. In this case, the g-line (436 nm in wavelength), h-line (405 nm in wavelength) or i-line (365 nm in wavelength) of a mercury vapor lamp, or an excimer laser, such as KrF (248 nm in wavelength), ArF (193 nm in wavelength) or F2 (157 nm in wavelength) is used as a light source. The shorter the wavelength of light used is, the finer is the pattern that will be produced. Accordingly, it is advantageous to employ a deep UV such as an excimer laser. Further, if an electron ray or an X-ray, which are still shorter in wavelength is employed, a still finer pattern will be obtained.
However, since the conventional resist is large in absorbency to the deep UV, it is impossible in the case of the conventional resist to allow the exposure light to pass into the full depth of the resist film. Accordingly, the sectional shape of pattern to be formed with the conventional resist is different in width between the surface and the bottom thereof. Tamely, if the resist is of positive type, the width at the surface thereof is smaller than that of the bottom, and if the resist is of negative type, the width at the bottom thereof is smaller than that of the surface. In either cases, it raises a problem of deterioration in effectiveness of the resist as an etching mask.
Examples of this chemically amplified resist are a positive type resist comprising a polymer wherein a hydroxyl group of poly(p-hydroxystyrene) is blocked by a butoxycarbonyl group, and an onium salt, which is a photo-acid generator (H. Ito, C. G. Wilson, J. M. J. Frechet, U.S. Pat. No. 4,491,628 (1985)); a positive type resist comprising an m-cresol novolak resin, naphthalene-2-carboxylic acid-tert-butylester and a triphenylsulfonium salt (a photo-acid generator) (M. J. O'Brien, J. V. Crivello, SPIE Vol. 920, Advances in Resist Technology and Processing, p42, (1988)); and a positive type resist comprising 2,2-bis(4-tert-butoxycarbonyloxyphenyl) propane or polyphthalaldehyde and an onium salt (a photo-acid generator) (H. Ito, SPIE Vol. 920, Advances in Resist Technology and Processing, p33, (1988)).
However, since the chemically amplified resists are highly sensitive, it is vulnerable to airborne basic substances and other minority components in the atmosphere. This vulnerability of the resist is reported for example by S. A. MacDonald, et. al., SPIE vol. 1466, Advance in Resist Technology and Processing P2, (1991). For example, dimethylaniline in the atmosphere inactivates the acid generated on the surface of the resist film. As a result, so-called sparingly soluble layer which is very slow in solubility rate to a developing solution is formed on the surface of the resist film. This sparingly soluble layer is left remained in the shape of "T-top" on the surface of the resist pattern after the development step. On the other hand, the sectional shape of the resist pattern to be obtained will be such that the width of opening on the substrate side becomes wider than that on the surface thereof, i.e. the angle between the side wall of the pattern and the surface of the substrate is more likely to become smaller than the ideal angle of 90° so that it would be impossible to form a pattern of rectangular shape in cross section.
Further, many of photo-acid generators in a chemically amplified resist composition react with the above mentioned basic compounds as these basic compounds are mixed into the resist thereby losing its capability of generating an acid. Even if the basic compound is weak in basicity, the reaction between the photo-acid generator and the basic compound proceeds slowly depending on the magnitude of the basicity. Because of this, it is difficult to obtain a resist which is capable of maintaining a stabilized property for a long period of time.
The object of the present invention is to provide a resist composition which is capable of forming a fine pattern having a more proper rectangular cross-section with a high resolution.
(a) a compound represented by the following formula (1) and satisfying the following inequalities; ##STR2## wherein R1 is hydrogen atom or methyl group, R2 is a monovalent organic group, m is 0 or a positive integer, n is a positive integer, and m and n satisfying a condition of 0.03≤n/(m+n)≤1;
4,000≤Mw≤50,000
The accompanying drawings, which are incorporated in and constitutes a part of the specification, illustrates a presently preferred embodiments of the invention and, together with the general description given above and the detailed description of the preferred embodiments given below, serves to explain the principles of the invention.
FIG. 1 is a sectional view of a resist pattern.
FIG. 2 are sectional views of patterns formed by use of a resist of Example (I-17), obtained on the basis of an X-ray photograph;
FIG. 3 are sectional views of patterns formed by use of a resist of Control (I-4), obtained on the basis of an X-ray photograph; and
FIG. 4 are sectional views of patterns formed by use of a resist of Control (I-5), obtained on the basis of an X-ray photograph.
The present inventors have found that the deterioration degree in shape of pattern due to the formation of the sparingly soluble layer on the surface of a resist film differs depending on the kinds of polymer, the kinds of the substituent group that inhibits the dissolution by protecting the alkali-soluble group, and the protection ratio of the alkali-soluble group. This invention has been accomplished on the basis of these findings.
R2 in the Formula (1) may be any kinds of monovalent organic group, examples of which are methyl, ethyl, p-propyl, iso-propyl, n-butyl, tert-butyl, iso-butyl, sec-butyl and benzyl.
If the value of molecular distribution Mw/Mn (Mn represents a number-average molecular weight as converted in styrene) is less than 1.10, a phase separation may be caused thus hindering the formation of uniform film. On the other hand, if the value of molecular distribution Mw/Mn exceeds over 2.5, the angle between the side wall of resist pattern and the surface of substrate becomes so small, thus resulting in a poor sectional shape of the pattern. Accordingly, the value of Mw/Mn should preferably be in the range of from 1.2 to 2.0.
Most preferable example of the compound represented by the Formula (1) is a compound represented by the following Formula (2); ##STR3## where q/(p+q) may range from 0.10 to 0.60.
The compound which is the (b) component of the resist composition according to the first invention, and capable of generating an acid when irradiated with chemical radiation can be selected from any of the known compounds. For example, various salts such as a diazonium salt, phosphonium salt, sulfonium salt and iodonium salt which accompany as a counter anion, such as CF3 SO3-, p-CH3 PhSO3-, p-NO2 PhSO3-- (where Ph is a phenyl group); an organic halogen compounds; ortho naphthoquinonediazido sulfonic ester can be used. Since an organic halogen compound, which is known as a photoinitiator for forming a free radical, is capable of forming a hydroacid halogenide, it can be used as a compound generating an acid under irradiation in the resist composition of the first invention.
As mentioned above, the resist composition according to the first invention comprises a polymer (component (a)) which is narrow in molecular distribution and capable of confining alkali-soluble group-protection ratio to a specific range, and a nitrogen-containing compound (component (c)). Through the employment of this resist composition, it is possible to prevent the formation of a pattern of poor sectional shape due to the formation of sparingly soluble-layer on the surface of a resist film, and to obtain, in a high sensitivity, a fine pattern having a more rectangular sectional shape when the resist is heated and developed after the exposure.
Examples of the nitrogen-containing compound (component (c)) are methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine,. di-n-propylamine, tri-n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, cyclohexylamine, di-n-butyulamine, tri-n-butylamine, benzylamine, α-phenylethylamine, β-phenylethylamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, aniline, methylaniline, dimethylaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, triphenylamine, o-toluidine, m-toluidine, o-anisidine, m-anisidine, p-anisidine, o-chloroaniline, m-chloroaniline, p-chloroaniline, o-bromoaniline, m-bromoaniline, p-bromoaniline, o-nitroaniline, m-nitroaniline, p-nitroaniline, 2,4-dinitroaniline, 2,4,6-trinitroaniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, benzidine, p-aminobenzoic acid, sulfanilic acid, sulfanilamide, pyridine, benzylpyridine, trimethylpyridine, 4-dimethylaminopyridine, piperidine, piperazine, urea, quinoline, methylquinoline, methoxyquinoline, isoquinoline, pyrazole, pyrazolone, imidazole, methylimidazole, triphenylimidazole, benzimidazole, nicotinamide, 2-benzimidazolinone, pyridazine, pyrimidine, triazole, nitrone, benzotriazole, purine, oxazole, indole, indazole, diaminodiphenyl sulfone, 1,3-bis(y-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and pyridinium salt. Among them, a pyridine compound is preferable. In particular, the following compounds are most preferable.
(2) A pyridine compound (a second pyridine compound) wherein two or more of substituted or non-substituted pyridine rings are combined to each other directly or indirectly through a divalent organic group consisting of carbon atom and hydrogen atom.
Examples of the pyridine compound having a substituent group such as the organic groups as mentioned above are 2-propylpyridine, 4-isopropylpyridine, 3-butylpyridine, 5-ethyl-2-methylpyridine, 5-butyl-2-methylpyridine, 2,4,6-trimethylpyridine, 2,4,6-triethylpyridine, 2-phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, 2,6-di-tert-butylpyridine, 2-(p-tolyl) pyridine, 2,6-diphenylpyridine, 2,6-di-p-tolylpyridine, 4-(1-butylpentyl) pyridine, 2-benzylpyridine, 2-(3-pentenyl) pyridine, 2-methoxypyridine, 2-butoxypyridine, and 2,6-dimethoxypyridine.
These polymer or copolymer can be synthesized according for example to the method described in the publication of "Shin Jikken Kagaku Kouza 19, High molecular chemistry I!, page 279 (1979), Nihon Kagakukai".
Examples of the group useful in protecting the alkali-soluble group in the compound of the component (e) are those groups which are unstable to an acid, e.g. a group having tertiary carbon atom such as a tert-butyl ester or tert-butyl carbonate of carboxylic acid as disclosed in Japanese Patent Unexamined Publication Hei-2-26660; a group having secondary carbon atom such as cyclohexyl, sec-butyl, or isopropyl as shown in Japanese Patent Unexamined Publication Sho-63-13943; trialkylsilyl or phenylsilyl as shown Japanese Patent Unexamined Publication Sho-60-52845; and tetrahydropyranyl or methylmethoxy as shown in Japanese Patent Unexamined Publication Hei-2-19847.
The solution of a resist composition prepared by dissolving the above mentioned components in an organic solvent is coated on the surface of a substrate by means of a spin-coating method. Then, the coated layer is dried at a temperature of 150° C. or less in general, or preferably at a temperature of 70° to 120° C. thereby forming a photosensitive resin layer (a resist film). The substrate to be employed in this case may be for example a silicon wafer; a silicon wafer having a stepped portion formed of insulating films, electrodes or interconnections; or a blank mask.
The resist film thus pattern-exposed is then subjected to a baking step generally at a temperature of about 40° to 160° C. for 30 to 600 seconds. If the baking temperature is less than 40° C., the acid generated from the component (b) can not be sufficiently reacted with the component (a). On the other hand, if the baking temperature exceeds beyond 160° C., a thermal decomposition may proceed even at the unexposed portion of the resist film thereby lowering the contrast of resist pattern to be finally obtained. Preferred baking temperature is in the range of about 70° to 140° C.
As for the etching gas to be used for a dry etching, for example CF4, C2 F6, CCl4, BCl3, Cl2 or HCl may be employed. These gases may be used in combination thereof.
Preferable examples of the component (a) are the compounds represented by the following formula (1). ##STR4##
wherein R1 is hydrogen atom or methyl group, R2 is a monovalent organic group, m is 0 or a positive integer, n is a positive integer, and m and n satisfying a condition of 0.03≤n/(m+n)≤1;
Examples of ester or ether which can be employed for introducing a substituent group (a protecting group) to be decomposed by an acid into the above mentioned phenol compound are methylester, ethylester, n-propylester, iso-propylester, tert-butylester, n-butylester, iso-butylester, benzylester, tetrahydropyranylether, benzylether, methylether, ethylether, n-propylether, iso-propylether, tert-butylether, allylether, methoxymethylether, p-bromophenacylether, trimethylsilylether, benzyloxycarbonylether, tert-butoxycarbonylether, tert-butylacetate, and 4-tert-butylbenzylether.
As for the compound which is capable of generating an acid upon irradiation of a chemical radiation, i.e. the component (b), there is no restriction, and any of known compounds can be employed. For example, various salts such as a diazonium salt, phosphonium salt, sulfonium salt and iodonium salt which accompany as a counter anion, such as CF3 SO3-, p-CH3 PhSO3-, p-NO2 PhSO3- (where Ph is a phenyl group); an organic halogen compounds; ortho naphthoquinonediazido sulfonic ester can be used in the same way as in the first invention.
Examples of the pyridinium salts are pyridinium-p-toluenesulfonate, 2-methylpyridinium-p-toluenesulfonate, 2-chloro-1-methylpyridinium-p-toluenesulfonate, 2,4,6-collidine-p-toluenesulfonate, 1-ethylpyridiniumchloride, 1-pentylpyridiniumchloride, 1-dodecylpyridiniumchloride, 1-hexadecylpyridiniumchloride, 1-benzyl-3hydroxypyridiniumchloride, 1-carboxymethylpyridiniumchloride, 2,6-dimethyl-1-methylpyridiniumchloride, 1,1'-dimethyl-4,4'-dipyridiniumdi chloride, 1,1'-dimethyl-4,4'-dimethyl-2,2'-dipyridiniumdichloride, 2,4'-dipyridiniumdichloride, 2,3'-dipyridiniumdichloride, 1,2-bis(4-pyridinium)ethane dichloride, 1,2-bis(2-pyridinium)ethylene dichloride, 2,2'-dithio bispyridiniumdichloride, and di-2-pyridinium ketone dichloride.
As examples of the component (c) of the second invention, the compounds represented by the following formula (3) to (6) are preferred. ##STR5##
wherein R3 is a non-substituted or substitute alkyl group having 1 to 30 carbon atoms; R4 to R11 may be the same with or different from each other, and represent individually hydrogen atom, non-substituted or substitute alkyl group, alkoxy group, acyl group, alkenyl group, hydroxyl group, amino group, dialkylamino group, nitro group, carboxy group, methoxycarbonyl group, ethoxycarbonyl group, carboxymethyl group, carboxyethyl group, carbamoyl group, phenyl group, tolyl group, xylyl group, mesityl group, benzyl group, styryl group, cinnamyl group, mercapto group, cyano group, and halogen atom; X- is an anion; Z represents divalent organic group; Y represents non-substituted or substituted alicyclic compound, aromatic compound or heterocyclic compound; and r is a positive integer.
The anion, X- in the pyridinium salts represented by the general formula (3) to (6) may be selected from halogen atoms, sulfate ion, perchlorate ion, sulfonate on, or an anion of halogen compounds of boron, aluminum, iron, zinc, arsenic, antimony and phosphorus.
These pyridinium salts can be synthesized according for example to the method described in the publication of "Jikken Kagaku Kouza 21, Synthesis of organic Compounds III, page 290 (1958), Nihon Kagakukai".
Among the pyridinium salts represented by the general formula (3) to (6), pyridinium salts with alkyl group represented by R3 having 10 or more carbon atoms are preferable in view of inhibiting the generation of the sparingly soluble layer. Namely, pyridinium salts with alkyl group represented by R3 having 10 or more carbon atoms act as a cation surfactant thus increasing the permeability of a developing solution to the sparingly soluble layer. Accordingly, the development process would proceed more smoothly. As the number of carbon atom in the above alkyl group represented by R3 is increased, the hydrophobic property of the pyridinium is proportionately enhanced, thereby lowering the dissolving rate of the resist film. Due to this reason, a difference in dissolution rate at the surface of the resist film is minimized so as to alleviate the influence of the sparingly soluble layer.
The solution of a resist composition prepared by dissolving the above mentioned components in an organic solvent is coated on the surface of a substrate by means of a spin-coating method. Then, the coated layer is dried under a temperature of 150° C. or less in general, or preferably at a temperature of 70° to 120° C. thereby forming a photosensitive resin layer (a resist film). The substrate to be employed in this case may be the same as explained in the case of the first invention. For example, a silicon wafer; a silicon wafer having a stepped portion formed of insulating films, electrodes or interconnections; or a blank mask. Additionally, it is possible to use a III-V group compound semiconductor wafer such as GaAs wafer and AlGaAs, or a piezoelectric wafer such as quartz and lithium tantalate.
The resist film thus pattern-exposed is then subjected to a baking step generally at a temperature of about 70° to 160° C., preferably at a temperature of 80° to 150° C. If the baking temperature is less than 70° C., the acid generated from the component (b) can not be sufficiently reacted with the component (a). On the other hand, if the baking temperature exceeds beyond over 160° C., a thermal decomposition or curing may proceed at the unexposed portion of the resist film as well as at the exposed portion thereof.
First, there will be explained about the resist composition of the first invention with references and controls.
The hydroxyl group of poly-4-hydroxystyrene was allowed to react with tert-butylbromoacetate to obtain a polymer having 30% of hydroxyl group thereof being introduced with tert-butoxycarbonylmethyl group. When GPC of this polymer was measured, the weight average molecular weight (Mw) thereof was found to be 25,000, and Mw/Mn was found to be 1.5 (Mn: number average molecular weight; Mw and Mn being converted in polystyrene). The polymer thus obtained will be referred to as a compound (A-1) hereinafter.
50 g of the compound (A-1), 0.65 g of tri-phenylmethanesulfonium tri-fluoromethane sulfonate (B-1), 88 mg of tri-n-butylamine (C-1) and 15 g of poly-4-hydroxystyrene (Mw: 7,000) (D-1) were dissolved into 260 g of ECA to obtain a solution. This solution was then filtered by using 0.2 μm mesh fluoroplastic membrane filter, thereby obtaining a solution (R-1) containing the resist composition of this invention.
This resist solution (R-1) was coated on the surface of a silicon wafer, and dried for 90 seconds by using a hot plate heated to 95° C., thereby obtaining a resist film 1.0 μm in thickness. Then, the resist film was exposed through a mask of prescribed pattern to light by using a reduced projection exposure apparatus provided with a light source of KrF excimer laser (248 nm), and then baked for 90 seconds on a hot plate heated to 95° C.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.25 μm in fineness had been formed with a light exposure of 50 mJ/cm2, that the angle of side wall 0.30 μm in width was 89.5°, and that the focus depth of the pattern was 1.6 μm. The angle of side wall herein indicated is an angle "a" between the substrate (1) and the side wall of pattern (2) as indicated in Figure.
Component (a) Examples of the compound represented by general formula (1) n/(m + n) Mw Mw/Mn
A-1 0.30 25,000 1.5
A-2 0.45 7,000 1.4
A-3 0.20 14,000 1.6
A-4 0.33 16,000 1.8
R2 = C(CH3)3
Component (b) Photo-acid generator
Component (c) Nitrogen-containing compounds
C-1 tri-n-butyl amine
C-2 tri-phenyl imidazole
C-3 2,4,6-tri-methyl pyridine
C-4 4,4'-di-amino-di-phenyl sulfone
C-5 2,2'-bipyridine
C-6 4,4'-bipyridine
C-7 5-butyl-2-methylpyridine
C-8 4-(1-butylpentyl)pyridine
C-9 2-benzylpyridine
C-10 4-tert-butylpyridine
C-11 1,2-bis(4-pyridyl)ethane
C-12 poly(4-vinylpyridine)
C-13 2-vinylpyridine-styrene copolymer
C-14 diphenyl amine
C-15 4,4'-di-amino-di-phenylmethane
C-16 pyridine
C-17 2-methyl pyridine
C-18 2-hydroxypyridine
C-19 nicotine amide
Component (d) Alkali-soluble polymer
D-1 poly-4-hydroxystyrene Mw 7,000
D-2 poly-4-hydroxystyrene Mw 2,000
D-3 m,p-cresol novolak Mw 2,300
D-4 styrene/acrylic acid copolymer (1/1)
Mw 5,000
D-5 poly-4-hydroxystyrene Mw 5,000
A resist solution was prepared in the same way as in the Example I-1, excepting that poly-4-hydroxystyrene (Mw: 20,000, Mw/Mn: 2.8) having 30% of hydroxyl group thereof being protected by tert-butoxycarbonylmethyl group (Compound P-1) was employed in place of the Compound A-1. This resist solution was employed in the same manner as in the Example I-1 to form a resist pattern. When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.30 μm in fineness could be formed, but a pattern of 0.25 μm in fineness could not be formed. The angle of side wall 0.30 μm in width was 85°, and that the focus depth of the pattern was 0.2 μm. It will be understood from the results that the resist pattern thus obtained was inferior in resolution, the angle of side wall and focus depth to the those of the Example I-1. The light exposure in this case was 48 mJ/cm2.
50 g of the Compound (A-1), 0.675 g of Compound (B-1), 91 mg of Compound (C-1), 17.5 g of Compound (D-1) and 1.4 g of Compound (E-1) as the component (e) were dissolved into 270 g of methyl-3-methoxypropionate (MMP) to obtain a solution. This solution was then filtered by using 0.2 μm mesh fluoroplastic membrane filter, thereby obtaining a solution (R-2) containing the resist composition of this invention.
When this resist pattern was evaluated of its exposure performance under the same conditions as in Example I-1, it indicated a resolution of 0.225 μm in width of patterned line. The angle of side wall 0.30 μm in width was 89.7°, and the focus depth of the pattern was 2.0 μm. The light of exposure was 45 mJ/cm2.
(Examples I-3 to I-12)
Various kinds of resist solutions having various compositions were prepared, and evaluated of their exposure performances under the same conditions as in Example I-1. The light exposure, resolution, and the angle of side wall of the pattern 0.30 μm in line width were shown in the following Table 4 together with the compositions of each resist solution.
Exposure Angle of side Component Component Component Component Component amount Resolution wall of pattern* (a) (b) (c) (d) (e) Solvent (mJ/cm2) (μm) (deg.)
A-1 B-1 C-1 D-1 ECA
I-1 50 g 0.65 g
88 mg 15 g 260 g 50 0.25 89.5
A-1 B-1 C-1 D-1 E-1 MMP
I-2 50 g 0.675 g
91 mg 17.5 g
270 g 45 0.225 89.7
A-1 B-1 C-1 D-2 E-1 MMP
I-3 50 g 0.65 g
88 mg 15 g 1.30 g
260 g 50 0.225 89.2
A-1 B-1 C-2 D-1 E-2 MMP
I-4 50 g 0.95 g
13 g 1.26 g
252 g 45 0.25 88.0
A-1 B-2 C-3 D-1 E-3 ECA
I-5 50 g 0.65 g
37 mg 15 g 1.95 g
260 g 60 0.225 89.0
A-1 B-2 C-4 D-4 E-4 ECA
I-6 50 g 0.68 g
39 mg 18 g 1.70 g
272 g 47 0.25 88.5
A-2 B-1 C-1 D-1 E-5 PGMEA
I-7 50 g 1.30 g
15 g 0.65 g
260 g 44 0.25 88.2
A-2 B-1 C-2 D-1 E-1 EL
I-8 50 g 1.00 g
18 g 3.40 g
332 g 37 0.25 88.7
A-2 B-2 C-3 D-2 E-2 EL
I-9 50 g 0.75 g
67 mg 13 g 3.15 g
308 g 52 0.225 89.0
A-2 B-3 C-4 D-2 E-3 ECA
I-10 50 g 1.26 g
89 mg 13 g 1.58 g
252 g 57 0.25 88.0
A-3 B-1 C-1 D-1 E-4 MMP
I-11 50 g 1.36 g
18 g 1.36 g
272 g 48 0.25 87.5
A-3 B-1 C-2 D-4 E-5 EEP
I-12 50 g 0.65 g
260 g 32 0.25 87.0
P-1 B-1 C-1 D-1 ECA
*0.30 μm in line width
50 g of the Compound (A-1), 4.8 g of Compound (B-1), 0.111 g of 2-benzyl pyridine and 18 g of Compound (D-1) were dissolved into 275 g of methyl-3-methoxypropionate (MMP) to obtain a solution. This solution was then filtered by using 0.2 μm mesh fluoroplastic membrane filter, thereby obtaining a solution (R-3) containing the resist composition of this invention.
This resist solution (R-3) was coated on the surface of a silicon wafer, and dried for 60 seconds by using a hot plate heated to 100° C., thereby obtaining a resist film 1.0 μm in thickness. Then, the resist film was exposed through a mask of prescribed pattern to X-rays, and then baked for 20 seconds on a hot plate heated to 80° C.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.15 μm in fineness had been formed with a light exposure of 170 mJ/cm2, and that the angle of side wall 0.30 μm in width was 89.0°.
(Example I-14)
The resist solution (R-3) of Example I-13 was coated on the surface of a silicon wafer, and dried for 60 seconds by using a hot plate heated to 110° C., thereby obtaining a resist film 0.80 μm in thickness. Then, the resist film was exposed to electron-rays, 20 kv in accelerating voltage to draw a pattern, and then baked for 120 seconds on a hot plate heated to 70° C.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.12 μm in fineness had been formed with a light exposure of 12 μC, and that the angle of side wall 0.30 μm in width was 89.5°.
(Example I-15)
50 g of the Compound (A-1), 9 g of Compound (B-4), 0.336 g of indole and 10 g of Compound (D-1) were dissolved into 240 g of methyl-3-methoxypropionate (MMP) to obtain a solution. This solution was then filtered by using 0.2 μm mesh fluoroplastic membrane filter, thereby obtaining a solution (R-4) containing the resist composition of this invention.
This resist solution (R-4) was coated on the surface of a silicon wafer, and dried for 90 seconds by using a-hot plate heated to 90° C., thereby obtaining a resist film 1.0 μm in thickness. Then, the resist film was exposed through a mask of prescribed pattern to light by using a reduced projection exposure apparatus provided with a light source of i-line (365 nm), and then baked for 60 seconds on a hot plate heated to 120° C.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.34 μm in fineness had been formed with a light exposure of 80 mJ/cm2, and that the angle of side wall 0.30 μm in width was 88.5°. The focus depth of this pattern was found to be 0.4 μm.
(Example I-16)
50 g of the Compound (A-1), 0.65 g of tri-phenylmethanesulfonium tri-fluoromethanesulfonate, (B-1), 0.88 mg of tri-n-butylamine (C-1), 29 mg of nicotinamide (C-19) and 15 g of poly-4-hydroxystyrene (Maruzen Sekiyu Kagaku Co. Ltd., linker PHM-C, Mw: 5,000) were dissolved into 320 g of ethyl lactate to obtain a solution. This solution was then filtered by using 0.2 μm mesh fluoroplastic membrane filter, thereby obtaining a solution of the resist composition of this invention.
This resist solution was coated on the surface of a silicon wafer, and dried for 90 seconds by using a hot plate heated to 100° C., thereby obtaining a resist film 1.0 μm in thickness. Then, the resist film was exposed through a mask of prescribed pattern to light by using a reduced projection exposure apparatus provided with a light source of KrF excimer laser (248 nm), and then is baked for 90 seconds on a hot plate heated to 90° C.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.225 μm in fineness had been formed with a light exposure of 60 mJ/cm2, and that the angle of side wall 0.30 μm in width was 89.5°. The focus depth of this pattern was found to be 2.0 μm.
A resist solution was prepared in the same way as in the Example I-15, excepting that poly-4-hydroxystyrene (Mw: 4,200, Mw/Mn: 1.7) having 30% of hydroxyl group thereof being protected by tert-butoxycarbonylmethyl group was employed in place of the Compound (A-1). This resist solution was employed in the same manner as in the Example I-15 to form a resist pattern. When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.40 μm in fineness could be formed, but a pattern of 0.34 μm in fineness could not be formed.
A resist solution was prepared in the same way as in the Example I-1, excepting that polyhydroxystyrene (Mw: 55,000, Mw/Mn: 1.5) having 28% of hydroxyl group thereof being protected by tert-butoxycarbonylmethyl group was employed in place of the Compound (A-1). This resist solution was coated on the surface of a silicon wafer, and dried over a hot plate heated to 95° C. for 90 seconds. When the section of this resist pattern was observed, the surface of the resist film was found to be non-uniform, and an irregular surface due to a phase separation was found all over the surface of the wafer.
EXAMPLE I-17)
As a component (a), a polymer expressed by the following chemical formula was prepared. ##STR13## The polymer had a weight-average molecular weight Mw of 27,000, Mw/Mn=1.51 (Mn: number average molecular weight), and n/(m+n)=0.28. Then, 10 g of the polymer, 0.13 g of triphenyl sulfonium trifluoromethane sulfonate as a component (b), 0.017 g of 4-phenylpyridine (triphenylsulfoniumtrifluoromethanesulfonate/4-phenylpyridine=1:0.35, in molar ratio) as a component (c) and 3 g of poly-4-hydroxystylene (Mw=8,000, Mw/Mn=2.3) as component (d) were dissolved into 72 g of ethyl lactate to obtain a solution. The solution was filtrated with a membrane filter having a mesh of 0.2 μm, thus obtaining a resist solution of Example (I-17).
With use of the resist solution thus obtained, a resist pattern was obtained in the following manner. First, an anti-reflection film was formed on a silicon wafer having a diameter of 8 inches. The obtained resist solution was applied on the anti-reflection film, and dried by heat on a hot plate at a temperature of 98° C. for 120 seconds. Subsequently, via a mask having a predetermined pattern, the resist film was exposed by a KrF excimer laser stepper (NA=0.5). After the exposure, the resist film was baked on the hot plate at a temperature of 98° C. for 120 seconds. Then, after the baking, the resist film was developed by a developer solution (AD-10 of Tama Kagaku (Chemicals) Corporation) for 60 seconds, thus obtaining a resist pattern.
A cross section of thus obtained resist pattern was observed under a scanning-type electron microscope (SEM), and the following fact was found. That is, a pattern of 0.20 μm in line width was formed at a light exposure of 46 mJ/cm2 and the height of the pattern was 0.91 μm. With regard to this 0.20 μm-pattern, no footing was observed on the surface of the substrate. The angle of the side wall of the pattern of 0.30 μm in line width was 89.3°.
FIG. 2 show sectional views of the resist pattern formed by use of the resist of this example, on the basis of a photograph thereof, taken under the microscope. FIG. 2A shows a pattern of 0.30 μm in line width, and FIG. 2B shows a pattern of 0.20 μm in line width. As can be understood from these figures, with the use of the resist of this example, the pattern 3 having a line width of 0.30 μm can be formed with a sufficiently large angle of a side wall, and the pattern 4 having a line width of 0.20 μm can be formed without thinning of film or footing on the surface of the substrate 1.
(Control I-4)
A resist solution was prepared in the same manner as that of Example (I-17) above, except that 4-phenyl pyridine was replaced by 0.017 g of 2-phenyl pyridine. With the use of thus obtained resist solution, the application of solution, exposure and development were carried out in the same manner as those of the above Example, thus obtaining a resist pattern.
From the observation of a cross section of thus obtained pattern under a SEM, it was found that a pattern of 0.225 μm in line width was formed with a light exposure of 39 mJ/cm2. In the pattern of 0.20 μm in line width, a footing occurred on the surface of the substrate, and patterns adjacent to each other are brought into contact with each other at a region close to the substrate. A desired pattern was not resolved. The height of this 0.20 μm pattern was 0.56 μm, and the thinning of film occurred in great deal as compared to the case of Example (I-17). The angle of side wall of the pattern of 0.30 μm in line width was 88.0°.
FIG. 3 show sectional views of the resist pattern formed by use of this comparative example, on the basis of a photograph thereof taken under the microscope. FIG. 3A shows a pattern of 0.30 μm in line width, and FIG. 3B shows a pattern of 0.20 μm in line width. As can be understood from these figures, with use of the resist of this comparative example, the pattern 5 having a line width of 0.30 μm can be formed with a small angle of a side wall, and the pattern 6 having a line width of 0.20 μm can be formed with footing created on the surface of the substrate 1, and a great amount of thinning of the film occurred.
(Control I-5)
A resist solution was prepared in the same manner as that of the Example (I-17) above, except that 4-phenyl pyridine was replaced with 0.019 g of 2-phenyl pyridine. With the use of the thus obtained resist solution, the application of the solution, exposure and development were carried out in the same manner as those of the above Example, thus obtaining a resist pattern.
From the observation of a cross section of thus obtained pattern under a SEM, it was found that a pattern of 0.20 μm in line width was formed with a light exposure of 50 mJ/cm2. The height of this 0.20 μm-pattern was 0.55 μm, and the thinning of the film occurred in great deal as compared to the case of Example (I-17). The angle of the side wall of the pattern of 0.30 μm in line width was 88.3°.
FIG. 4 show sectional views of the resist pattern formed by use of the resist of this comparative example, on the basis of a photograph thereof taken under the microscope. FIG. 4A shows a pattern of 0.30 μm in line width, and FIG. 4B shows a pattern of 0.20 μm in line width. As can be understood from these figures, with the use of the resist in this comparative example, the pattern 7 having a line width of 0.30 μm can be formed with a great amount of thinning of the film.
Followings are examples where pyridine compounds are used as the component (c) of the resist composition of the first invention.
(Examples II-1 to II-10, and Controls II-1 to II-7)
(Synthesis of a compound to be decomposed by an acid)
50 g of polyvinylphenol (Mw=13,000) was dissolved into 200 ml of acetone in a four-necked flask purged with nitrogen gas, thus obtaining a solution. To this solution were added 17.63 g of potassium carbonate, 8.48 g of potassium iodide and 24.38 g of tert-butylbromoacetate, and the resultant mixture was refluxed for 7 hours under stirring. After removing insolubles through filtration, acetone was removed through a distillation, thereby leaving a residue, which was subsequently dissolved into 150 ml of ethanol. The solution thus obtained was dripped into 1,500 ml of water, thereby precipitating a polymer. After being filtered, the polymer was washed 5 times with 300 ml of water, and then dried in air for 12 hours.
Subsequently, the polymer was again dissolved into 220 ml of ethanol, and processed in the same manner as explained above thereby to re-precipitate and refine the polymer. The refined polymer was dried for 24 hours in a vacuum desiccator heated to 50° C. to obtain 50.0 g of polymer. It was found as a result of measurement of this polymer by 1 H-NMR spectrum that 33% of hydroxyl group in polyvinyl phenol had been converted into tert-butoxycarbonyl methylether. By the way, when the GPC of this polymer was measured, the weight average molecular weight was found to be 16,000, and Mw/Mn was found to be 1.8 (Mn: number average molecular weight; Mw and Mn being converted in polystyrene). The polymer thus obtained is denoted as Compound (A-4), has the following chemical formula. ##STR14## (Preparation of a resist composition)
Exposure Angle of side Component Component Component Component amount Resolution wall of pattern* (a) (b) (c) (d) Solvent (mJ/cm2) (μm) (deg.)
A-4 B-5 C-5 -- EL
II-1 23.0 g
0.8 g 20 mol % 76.2 g
53 0.30 88.5
A-4 B-4 C-6 D-5 ECA
II-2 21.0 g
2.8 g 20 mol %
3.0 g 73.2 g
60 0.30 88.5
A-4 B-1 C-7 D-5 MMP
II-3 14.0 g
0.3 g 35 mol %
6.0 g 79.7 g
40 0.25 89.0
A-4 B-1 C-3 D-5 MMP
II-4 14.0 g
29 0.25 89.5
A-4 B-1 C-8 D-5 MMP
II-5 14.0 g
37 0.25 89.0
A-4 B-1 C-9 D-5 MMP
II-6 14.0 g
40 0.25 89.5
A-4 B-1 C-10 D-5 MMP
II-7 14.0 g
55 0.25 89.5
A-4 B-1 C-11 D-5 MMP
II-8 14.0 g
0.3 g 15 mol %
42 0.25 89.0
A-4 B-1 C-12 D-5 MMP
II-9 14.0 g
0.3 g 0.1 wt %
30 0.25 89.9
A-4 B-1 C-13 D-5 MMP
II-10 14.0 g
22 0.25 89.5
A-4 B-5 C-14 -- EL
II-11 23.0 g
76 0.35 88.0
A-4 B-4 C-15 D-5 ECA
II-12 21.0 g
85 0.35 88.5
A-4 B-1 C-16 D-5 MMP
II-13 14.0 g
42 0.30 87.0
A-4 B-1 C-17 D-5 MMP
II-14 14.0 g
36 0.25 87.0
A-4 B-1 C-18 D-5 MMP
II-15 14.0 g
50 0.30 87.0
A-4 B-1 C-19 D-5 MMP
II-16 14.0 g
78 0.30 86.0
A-4 B-1 C-20 D-5 MMP
II-17 14.0 g
82 0.25 88.5
P-1 B-4 C-6 D-5 EL
II-1 21.0 g
3.0 g 85.0 g
65 0.30 85.5
P-2 B-1 C-7 D-5 MMP
II-2 14.0 g
35 0.40 Not patterned
P-3 B-1 C-3 D-5 MMP
32 0.30 85.5
MW MW/Mn n/(m + n)
P-1 20,000 2.8 0.30
P-2 3,000 2.0 0.65
P-3 12,000 2.9 0.17
The compounds shown in Tables 5 and 6 (Examples II-1, 2, 11, and 12) were spin-coated on the surface of a silicon wafer 6 inches in diameter, and subsequently pre-baked for 90 seconds over a hot plate heated to 100° C. thereby forming a resist film 1.0 μm in thickness. Then, this resist film was exposed to light by using an i-line stepper (NA=0.50) to form a pattern of exposure. Subsequently, the resist film was baked for 90 seconds over a hot plate heated to 100° C. Then, the baked resist film was subjected to a developing process by immersing it in a 2.38% aqueous solution of TMAH for 45 seconds, and washing it with water, thereby obtaining a resist pattern.
The-compounds shown in Tables 5 and 6 (Examples II-3 to II-10 and II-13 to 17) were spin-coated on the surface of a silicon wafer 6 inches in diameter, and subsequently pre-baked for 90 seconds over a hot plate heated to 95° C. thereby forming a resist film 1.0 μm in thickness. Then, this resist film was exposed to light by using a KrF excimer laser stepper (NA=0.45) to form a pattern of exposure. Subsequently, the resist film was baked for 90 seconds over a hot plate heated to 95° C. Then, the baked resist film was subjected to a developing process by immersing it in a 2.38% aqueous solution of TMAH for 60 seconds, and washing it with water, thereby obtaining a resist pattern.
The resist composition of the second invention will be explained in detail with reference to the following Examples and Controls.
(Examples III-1 to III-6, and Controls III-1 to III-4)
(Preparation of a resist composition)
Component Component Component Component Maintenance (a) (b) (c) (d) Solvent factor (%)
A-5 B-5 CC-1 -- EL 100
III-1 23.0 g
2.0 g 20 mol% 75.0 g
A-5 B-5 CC-2 -- EL 100
III-2 23.0 g
2.0 g 20 mol % 75.0 g
A-5 B-5 CC-2 -- EL 99
III-3 23.0 g
2.0 g 30 mol % 75.9 g
A-6 B-4 CC-3 DD-2 ECA 100
III-4 16.2 g
60 g 75.0 g
A-5 B-1 CC-4 DD-1 MMP 100
III-5 21.0 g
1.0 g 15 mol %
3.0 g 75.0 g
A-5 B-1 CC-5 DD-1 MMP 100
III-6 21.0 g
A-5 B-5 C-14 -- EL 88
A-5 B-5 C-15 -- EL 80
A-6 B-4 C-18 DD-2 ECA 85
III-3 16.2 g
6.0 g 75.0 g
A-6 B-4 C-19 DD-2 ECA 82
Compounds having a substituent group to be decomposed by an acid ##STR15##
Pyridinium salts CC-1 2,4,6-collidine-p-toluenesulfonate CC-2 cetylpyridinium chloride CC-3 dodecylpyridinium chloride CC-4 1,1'-diheptyl-4,4'-bipyridinium chloride CC-5 1,1'-dibenzyl-4,4'-bipyridinium chloride Alkali-soluble polymer DD-1 DD-2 ##STR16##
The resist composition having the same composition of Example III-5 described in the Table 8 was spin-coated on the surface of a silicon wafer 6 inches in diameter, and subsequently pre-baked for 90 seconds over a hot plate heated to 100° C. thereby forming a resist film 1.0 μm in thickness. Then, this resist film was exposed to light by using a KrF excimer laser stepper (NA=0.45) to form a pattern of exposure. Subsequently, the resist film was baked for 90 seconds over a hot plate heated to 95° C. Then, the baked resist film was subjected to a developing process by immersing it in a 2.38% aqueous solution of TMAH for 50 seconds, and washing it with water, thereby obtaining a resist pattern.
When the section of this resist pattern was observed with a scanning type electron microscope, it was found that a pattern of 0.25 μm in fineness had been formed with a light exposure of 32 mJ/cm2. Further, the sectional shape of the pattern was rectangular, and the generation of overhang was not admitted at all.
The resist composition having the same composition of Example III-2 described in the Table 8 was spin-coated on the surface of a silicon wafer 6 inches in diameter, and subsequently pre-baked for 90 seconds over a hot plate heated to 100° C. thereby forming a resist film 1.0 μm in thickness. Then, this resist film was exposed to light by using an i-line stepper (NA=0.50) to form a pattern of exposure. Subsequently, the resist film was baked for 90 seconds over a hot plate heated to 100° C. Then, the baked resist film was subjected to a developing process by immersing it in a 2.38% aqueous solution of TMAH for 40 seconds, and washing it with water, thereby obtaining a resist pattern.
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