A positive photoresist composition which comprises (A) a resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution, and (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation.

The present invention relates to a positive photosensitive composition for use in the production of a lithographic printing plate, a semiconductor such as IC, a circuit board for liquid crystal and thermal head and in other photofabrication processes.
As the photosensitive composition for use in the production of a lithographic printing plate, a semiconductor such as IC, a circuit board for liquid crystal and thermal head and in other photofabrication processes, various compositions are known and photoresist photosensitive compositions are ordinarily employed. The photoresist compositions are widely divided into positive photoresist compositions and negative photoresist compositions.
One of the positive photoresist photosensitive compositions is a chemical amplification-type resist composition as described in U.S. Pat. No. 4,491,628 and European Patent No. 249,139. The chemical amplification-type positive resist composition is a pattern formation material which generates an acid in an exposed area upon irradiation with a radiation such as a far ultraviolet ray and due to a reaction using the acid as a catalyst, solubility in a developing solution differentiates in the area irradiated with the active radiation from the non-irradiated area to form a pattern on a substrate.
Examples of such a resist composition include combinations of a compound capable of generating an acid by photolysis with an acetal or O,N-acetal compound as described in JP-A-48-89003 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), with an ortho ester or amide acetal compound as described in JP-A-51-120714, with a polymer having an acetal or ketal group on the main chain as described in JP-A-53-133429, with an enol ether compound as described in JP-A-55-12995, with an N-acyliminocarbonic acid compound as described in JP-A-55-126236, with a polymer having an ortho ester group on the main chain as described in JP-A-56-17345, with a tertiary alkyl ester compound as described in JP-A-60-3625, with a silyl ester compound as described in JP-A-60-10247 or with a silyl ether compound as described in JP-A-60-37549 and JP-A-60-121446. These combinations exhibit high photosensitivity since they have in principle a quantum yield exceeding 1.
A system which is stable at a room temperature but decomposes by heating in the presence of an acid to become alkali-soluble is also known and examples thereof include combinations of a compound capable of generating an acid on exposure with an ester or carbonic acid ester compound having a tertiary or secondary carbon (e.g., tert-butyl or 2-cyclohexenyl) as described, for example, in JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240, JP-A-63-250642, Polym. Eng. Sce., Vol. 23, page 1012 (1983), ACS. Sym., Vol. 242, page 11 (1984), Semiconductor World, November, 1987, page 91, Macromolecules, Vol. 21, page 1475 (1988), and SPIE, Vol. 920, page 42 (1988). Since such a system has high photosensitivity and a little absorption in a far ultraviolet region, it is suitable for ultra fine fabrication using a light source having a shorter wavelength.
In general, the chemical amplification-type positive photoresist composition is roughly divided into two types. Specifically, there are a chemical amplification positive photoresist of three-component type comprising an alkali-soluble resin, a compound capable of generating an acid upon irradiation with a radiation (hereinafter also referred to as a xe2x80x9cphoto-acid generatorxe2x80x9d sometimes) and a compound which has an acid-decomposable group and prevents the alkali-soluble resin from dissolution and a chemical amplification positive photoresist of two-component type comprising a resin having a group capable of being decomposed by a reaction with an acid to become alkali-soluble and a photo-acid generator.
The two-component or tree-component chemical amplification positive photoresist composition is subjected to exposure to generate an acid from the photo-acid generator, heat treatment and development thereby obtaining a resist pattern.
These chemical amplification-type positive photoresist compositions are suitable for ultra fine fabrication using a light source having a shorter wavelength as described above. However, further improvements in resolution and process allowance such as exposure margin and depth of focus have been desired.
A basic sulfonium compound is described as a photo-acid generator in JP-A-6-242606. A basic iodonium compound is described as a photo-acid generator in JP-A-7-333844. Also, the use of a compound generating a carboxylic acid together with a compound generating an acid other than a carboxylic acid is described as a photo-acid generator in JP-A-11-125907.
However, such a technique is still insufficient for meeting the ultra fine fabrication today and further improvements in resolution and process allowance such as exposure margin and depth of focus have been desired.
Therefore, an object of the present invention is to provide a positive photoresist composition which is improved in resolution and process allowance such as exposure margin and depth of focus in a lithographic technology using a light source having a short wavelength capable of conducting the ultra fine fabrication and a chemical amplification-type positive photoresist.
Other objects of the present invention will become apparent from the following description.
It has been found that the objects of the present invention are accomplished by the following positive photoresist compositions:
(1) a positive photoresist composition which comprises (A) a resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution, and (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation,
(2) the positive photoresist composition as described in item (1) above, wherein the composition further comprises (D) a compound having a molecular weight of not more than 3,000 which decomposes by the action of an acid to increase solubility in an alkaline developing solution,
(3) a positive photoresist composition which comprises (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation, (D) a compound having a molecular weight of not more than 3,000 which decomposes by the action of an acid to increase solubility in an alkaline developing solution, and (E) an alkali-soluble resin,
(4) the positive photoresist composition as described in any one of items (1) to (3) above, wherein the composition further comprises (C) a compound which generates a sulfonic acid upon irradiation with an actinic ray or radiation,
(5) the positive photoresist composition as described in any one of items (1) to (4) above, wherein the composition further comprises (F) a nitrogen-containing basic compound and (G) a fluorine-base or silicon-base surface active agent,
(6) the positive photoresist composition as described in any one of items (1) to (5) above, wherein (B) the compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation is a compound represented by the following formula (I), (II) or (III):
wherein R1 to R37, which may be the same or different, each represents a hydrogen atom, a straight chain, branched chain or cyclic alkyl group, a straight chain, branched chain or cyclic alkoxy group, a hydroxy group, a halogen atom or an xe2x80x94Sxe2x80x94R38 group (wherein R38 represents a straight chain, branched chain or cyclic alkyl group or an aryl group); and Xxe2x88x92 represents an anion of an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom,
(7) the positive photoresist composition as described in item (6) above, wherein Xxe2x88x92 represents an anion of a perfluoro aliphatic carboxylic acid or a perfluoro aromatic carboxylic acid,
(8) the positive photoresist composition as described in item (6) above, wherein Xxe2x88x92 represents an anion of a perfluoro alkyl carboxylic acid having not less than 4 carbon atoms,
(9) the positive photoresist composition as described in any one of items (1), (2) and (4) to (8) above, wherein (A) the resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution is a resin containing a repeating unit represented by formula (IV) shown below and a repeating unit represented by formula (V) shown below.
wherein L represents a hydrogen atom, a straight-chain, branched chain or cyclic alkyl group which may be substituted or an aralkyl group which may be substituted; Z represents a straight-chain, branched chain or cyclic alkyl group which may be substituted or an aralkyl group which may be substituted; or Z and L may be combined with each other to form a 5-membered or 6-membered ring,
(10) the positive photoresist composition as described in item (9) above, wherein Z in formula (IV) represents a substituted alkyl group or a substituted aralkyl group, and
(11) the positive photoresist composition as described in any one of items (1) to (10) above, wherein the composition further comprises (Bxe2x80x2) a compound which generates a carboxylic acid which is not substituted with a fluorine atom upon irradiation with an actinic ray or radiation.
As described above, the use of a compound generating a carboxylic acid together with a compound generating an acid other than a carboxylic acid as a photo-acid generator is described in JP-A-11-125907. The compound generating a carboxylic acid does not directly contribute to decomposition of an acid-decomposable group, since the carboxylic acid generated is a weak acid. Accordingly, when the compound generating a carboxylic acid is used alone as a photo-acid generator, severe problems in that an image cannot be formed and in that sensitivity remarkably decreases occur. Therefore, the compound generating a carboxylic acid cannot be used alone as a photo-acid generator and it must be used together with a photo-acid generator which generates a strong acid.
The present inventors have found that the compound generating a carboxylic acid can be used alone by introducing a specific substituent thereto to solve these problems successfully and provide a photoresist composition having excellent performance.
The photoresist composition of the present invention also has excellent performance when an electron beam is used as a light source for exposure. In the case of exposing a photoresist to an electron beam, the incident electron has an electric charge and interacts with an atomic nucleus and electron of a substance constituting the resist. Therefore, scattering of the electron beam is sure to occur during the incidence of the electron beam to the resist film. As a result, a problem of degradation of pattern profile occurs. Even when a beam diameter is stopped down at the time of exposure in order to resolve a fine pattern, the exposed area is expanded due to the scattering and a problem of deterioration of resolution occurs. These problems on the exposure with an electron beam can also be solved splendidly according to the photoresist composition of the present invention.
The positive photoresist composition of the present invention includes
(1) a positive photoresist composition comprising (A) a resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution and (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation as the indispensable components (hereinafter also referred to as a xe2x80x9cfirst compositionxe2x80x9d) and
(2) a positive photoresist composition comprising (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation, (D) a compound having a molecular weight of not more than 3,000 which decomposes by the action of an acid to increase solubility in an alkaline developing solution and (E) an alkaline-soluble resin as the indispensable components (hereinafter also referred to as a xe2x80x9csecond compositionxe2x80x9d).
The term xe2x80x9cpositive photoresist compositionxe2x80x9d or xe2x80x9ccompositionxe2x80x9d used hereinafter includes both the first composition and the second composition.
The components including the compounds and resins for use in the positive photoresist composition of the present invention will be described in greater detail below.
 less than Components Included in the Positive Photoresist Composition greater than
[1] (B) A compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation (Component (B)):
The positive photoresist composition contains the component (B) as the indispensable component.
Specific examples of the aliphatic carboxylic acid substituted with a fluorine atom of component (B) include a fluorine-substituted compound of an aliphatic carboxylic acid, for example, acetic acid, propionic acid, n-butyric acid, isobutyric acid, valerianic acid, trimethylacetic acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, undecanoic acid, dodecanoic acid and tridecanoic acid. The aliphatic carboxylic acid may have a substituent, for example, a hydroxy group, an alkoxy group or a halogen atom (excluding a fluorine atom). Further, the aliphatic carboxylic acid which contains a linking group, for example, an oxygen atom, a sulfur atom, a carbonyl group, a carboxy group or a sulfonyl group in the aliphatic chain thereof is preferred.
Preferred examples of the aliphatic carboxylic acid substituted with a fluorine atom include those represented by the following formula (VI):
Lxe2x80x94(CH2)p(CF2)q(CH2)rxe2x80x94COOHxe2x80x83xe2x80x83(VI)
wherein L represents a hydrogen atom or a fluorine atom; p and r, which may be the same or different, each represents an integer of from 0 to 15; and q represents an integer of from 1 to 15.
The hydrogen atom or fluorine atom on the alkyl chain present in the compound represented by formula (VI) may be substituted with an alkyl group preferably having from 1 to 5 carbon atoms which may be substituted with a fluorine atom, an alkoxy group preferably having from 1 to 5 carbon atoms which may be substituted with a fluorine atom or a hydroxy group.
The aliphatic carboxylic acid substituted with a fluorine atom preferably includes a fluorine-substituted saturated aliphatic carboxylic acid having from 2 to 20 carbon atoms, preferably from 4 to 20 carbon atoms. By the use of the fluorine-substituted saturated aliphatic carboxylic acid having not less than 4 carbon atoms, diffusibility of the carboxylic acid generated decreases and change in line width due to the lapse of time from exposure to post baking is further prevented. Of the aliphatic carboxylic acids substituted with a fluorine atom, a fluorine-substituted compound of a saturated straight-chain or branched chain aliphatic carboxylic acid having from 4 to 18 carbon atoms is preferred.
The aromatic carboxylic acid substituted with a fluorine atom preferably includes a fluorine-substituted aromatic carboxylic acid having from 7 to 20 carbon atoms, preferably from 7 to 15 carbon atoms and more preferably from 7 to 11 carbon atoms.
Specific examples thereof include a fluorine-substituted compound of an aromatic carboxylic acid, for example, benzoic acid, a substituted benzoic acid, naphthoic acid, a substituted naphthoic acid, anthracenecarboxylic acid or a substituted anthracenecarboxylic acid (wherein the substituent including, for example, an alkyl group, an alkoxy group, a hydroxy group, a halogen atom (excluding a fluorine atom), an aryl group, an acyl group, an acyloxy group, a nitro group, an alkylthio group or an arylthio group). Of the aromatic carboxylic acids substituted with a fluorine atom, a fluorine-substituted compound of benzoic acid or a substituted benzoic acid is preferred.
The aliphatic or aromatic carboxylic acid substituted with a fluorine atom is a compound wherein at least one hydrogen atom attached to the skeleton other than the carboxylic group is substituted with a fluorine atom. Particularly, an aliphatic or aromatic carboxylic acid wherein all of hydrogen atoms attached to the skeleton other than the carboxylic group are substituted with fluorine atoms (preferably a perfluoro saturated aliphatic carboxylic acid or a perfluoro aromatic carboxylic acid) is preferred. The perfluoro aliphatic or aromatic carboxylic acid is excellent for further improvement in sensitivity.
Preferred components (B) include an onium salt compound (e.g., sulfonium salt or iodonium salt) having an anion of the aliphatic or aromatic carboxylic acid substituted with a fluorine atom described above as a counter anion, an imidocarboxylate compound having a carboxylic acid ester and a nitrobenzyl ester compound.
Compounds represented by formula (I), (II) or (III) described above are more preferred for the component (B). These compounds are excellent for further improvement in sensitivity, resolution and exposure margin. The compound generates an aliphatic (preferably an aliphatic) or aromatic carboxylic acid substituted with at least one fluorine atom corresponding to Xxe2x88x92 in formula (I), (II) or (III) upon irradiation with an actinic ray or radiation thereby acting as a photo-acid generator.
In formulae (I), (II) and (III), examples of the straight-chain or branched chain alkyl group represented by R1 to R38 include those having from 1 to 4 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group) which may have a substituent. Examples of the cyclic alkyl group represented by R1 to R38 include those having from 3 to 8 carbon atoms (e.g., a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group) which may have a substituent. Examples of the straight-chain or branched chain alkoxyl group represented by R1 to R37 include those having from 1 to 4 carbon atoms (e.g., a methoxy group, an ethoxy group, a hydroxyethoxy group, a propoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group) which may have a substituent.
Examples of the cyclic alkoxyl group represented by R1 to R37 include those having from 5 to 6 carbon atoms (e.g., a cyclopentyloxy group, and a cyclohexyloxy group).
Examples of the halogen atom represented by R1 to R37 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Example of the aryl group represented by R38 include those having from 6 to 14 carbon atoms (e.g., a phenyl group, a tolyl group, a methoxyphenyl group, and a naphthyl group) which may have a substituent.
Examples of the substituent for the above-described group include an alkoxyl group having from 1 to 4 carbon atoms, a halogen atom (e.g., a fluorine atom, a chlorine atom, and an iodine atom), an aryl group having from 6 to 10 carbon atoms, an alkenyl group having from 2 to 6 carbon atoms, a cyano group, a hydroxy group, a carboxy group, an ankoxycarbonyl group, and a nitro group.
The iodonium compound or sulfonium compound represented by formula (I), (II) or (III) for use in the present invention has an anion of the aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom as the counter anion represented by Xxe2x88x92. Such an anion is an anion (xe2x80x94COOxe2x88x92) formed by releasing a hydrogen atom from the carboxylic acid (xe2x80x94COOH).
Specific examples of the compound (photo-acid generator) of component (B) are set forth below, however, the present invention should not be construed as being limited thereto.
Specific examples (I-1) to (I-36) of the photo-acid generator represented by formula (I):
Specific examples (II-1) to (II-67) of the photo-acid generator represented by formula (II):
Specific examples (III-1) to (III-4) of the photo-acid generator represented by formula (III):
Specific examples (VI-1) to (V-4) of the photo-acid generator other than those represented by formulae (I) (II) and (III):
The compounds of component (B) may be used individually or in combination of two or more thereof.
The compound represented by formula (I) of component (B) can be synthesized by reacting an aromatic compound with a periodate and subjecting the resulting iodonium salt to salt exchange with a corresponding carboxylic acid.
The compound represented by formula (II) or (III) can be synthesized, for example, by a method comprising reacting an aryl Grignard reagent such as arylmagnesium bromide with a substituted or unsubstituted phenyl sulfoxide and subjecting the resulting triarylsulfonium halide to salt exchange with a corresponding carboxylic acid, a method comprising condensing a substituted or unsubstituted phenyl sulfoxide and a corresponding aromatic compound using an acid catalyst, e.g., methanesulfonic acid/diphosphorus pentaoxide or aluminum chloride and subjecting the resulting product to salt exchange, or a method comprising condensing diaryliodonium salt and diaryl sulfide using a catalyst, e.g., copper acetate and subjecting the resulting product to salt exchange.
The salt exchange can be conducted by a method wherein the halide salt formed is converted to a carboxylic acid salt using a silver reagent such as silver oxide or a method using an ion-exchange resin. The carboxylic acid or carboxylic acid salt for use in the salt exchange can be selected from commercially available compounds or can be obtained by a method of hydrolyzing a commercially available carboxylic acid halide.
As the fluorine-substituted carboxylic acid for the anion portion of the compound of component (B), that derived from fluoro-aliphatic compound prepared by a telomerization method (also referred to as a telomer method) or an oligomerization method (also referred to as an oligomer method) is also preferably used. Methods for the preparation of the fluoro-aliphatic compound are described, for example, in Nobuo Ishikawa ed., Fussokagobutsu no Gosei to Kino (Syntheses and Functions of Fluorine Compounds), pages 117 to 118, CMC Co., Ltd. (1987) and Chemistry of Organic Fluorine Compounds II (Monograph 187, Ed. by Milos Hudlicky and Attila E. Pavlath, American Chemical Society 1995), pages 747 to 752.
The telomerization method is a method in which a fluorine-containing vinyl compound such as tetrafluoroethylene is subjected to a radical polymerization using an alkyl halide having a large chain transfer constant such as an iodide as a telogen to prepare a telomer (shown in Scheme 1 below). In the preparation by the telomer method, a mixture of plural compounds each having a different carbon chain length is obtained. The mixture may be used as it is or after purification.
The terminal iodinated telomer is usually subjected to appropriate terminal chemical modification as shown in Scheme 2 below to prepare a fluoro-aliphatic compound. The resulting compound is further converted to a compound having the desired structure, if desired, and is employed for the preparation of the fluoro-aliphatic compound.
The content of the compound of component (B) is preferably from 0.1 to 20% by weight, more preferably from 0.5 to 10% by weight, still more preferably from 1 to 7% by weight, based on the solid content of the positive photoresist composition of the present invention.
[2] (C) A photo-acid generator which can be used together with the compound of component (B) (Component (C)):
In the positive photoresist composition of the present invention, a photo-acid generator other than the compound of component (B) can be used together with the compound of component (B).
The photo-acid generator which is used together with the compound of component (B) can be appropriately selected from photoinitiators for photo-cation polymerization, photoinitiators for photo-radical polymerization, photo-achromatizing agents for dyes, photo-discoloring agents, and compounds which generate an acid by radiation conventionally used in a microresist or the like (an ultraviolet ray or far ultraviolet ray of from 200 to 400 nm, particularly preferably, a g-line, h-line, i-line or KrF excimer laser beam), an ArF excimer laser beam, an electron beam, an X ray, a molecular beam or an ion beam. A mixture of these compounds can also be used.
Other examples of the photo-acid generator used together with the compound of component (B) include onium salts such as diazonium salts, ammonium salts, phosphonium salts, iodonium salts, sulfonium salts, selenonium salts or arsonium salts, organic halide compounds, organic metal/organic halide compounds, photo-acid generators having an o-nitrobenzyl-type protective group, compounds which photolyze to generate a sulfonic acid, represented by iminosulfonate and the like, disulfone compounds, diazoketosulfone compounds and diazodisulfone compounds.
Also, polymer compounds having the group or compound generating an acid by irradiation introduced into the main or side chain thereof may be used.
Further, compounds which generate an acid by irradiation as described in V. N. R. Pillai, Synthesis, (1), 1 (1980), A. Abad et al., Tetrahedron Lett., (47) 4555 (1971), D. H. R. Barton et al., J. Chem. Soc., (C), 329 (1970), U.S. Pat. No. 3,779,778 and European Patent 126,712 may be used.
Among the above-described compounds which decompose upon irradiation with an actinic ray or radiation to generate an acid, those which can be particularly effectively used include compounds represented by formula (PAG3), (PAG4), (PAG6) or (PAG7) described below.
In formulae (PAG3) and (PAG4), Ar1 and Ar2, which may be the same or different, each represents a substituted or unsubstituted aryl group. Preferred examples of the substituent include an alkyl group, a haloalkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitro group, a carboxyl group, an alkoxycarbonyl group, a hydroxy group, a mercapto group and a halogen atom.
R203, R204 and R205, which may be the same or different, each represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, preferably an aryl group having from 6 to 14 carbon atoms, an alkyl group having from 1 to 8 carbon atoms, or a substituted derivative thereof. Preferred examples of the substituent include, for the aryl group, an alkoxy group having from 1 to 8 carbon atoms, an alkyl group having from 1 to 8 carbon atoms, a nitro group, a carboxyl group, a hydroxyl group and a halogen atom, and for the alkyl group, an alkoxy group having from 1 to 8 carbon atoms, a carboxyl group and an alkoxycarbonyl group.
Zxe2x88x92 represents a counter anion. Examples of the counter anion include BF4xe2x88x92, AsF6xe2x88x92, PF6xe2x88x92, SbF6xe2x88x92, SiF62xe2x88x92, ClO4xe2x88x92, a substituted or unsubstituted alkanesulfonate anion, a perfluoroalkanesulfonate anion, a substituted or unsubstituted benzene sulfonate anion, a substituted or unsubstituted naphthalenesulfonate anion, a substituted or unsubstituted anthracene sulfonate anion and a substituted or unsubstituted camphorsulfonate anion, however, the present invention should not be construed as being limited thereto. Preferred examples of the counter anion include an alkanesulfonate anion, a perfluoroalkanesulfonate anion, an alkyl-substituted benzenesulfonate anion and pentafluorobenzenesulfonate anion.
Alternatively, two of R203, R204 and R205 or Ar1 and Ar2 may be combined through a single bond or a substituent.
In formulae (PAG6) and (PAG7), R206 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, A represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group or a substituted or unsubstituted arylene group, and R represents a straight-chain, branched chain or cyclic alkyl group or an aryl group which may be substituted.
Specific examples thereof include the following compounds, however, the present invention should not be construed as being limited thereto.
Among the photo-acid generators used together with the compound of component (B), (C) a compound which generates a sulfonic acid upon irradiation with an actinic ray or radiation is preferred in view of attaining improved sensitivity and resolution.
The positive photoresist composition of the present invention may contain a compound which generates a carboxylic acid upon irradiation with an actinic ray or radiation other than the compound of component (B) (hereinafter also referred to as Component (Bxe2x80x2)). By the use of such a compound, pitch dependency is improved.
Examples of the compound of component (Bxe2x80x2) include a compound represented by formula (I), (II) or (III) described above in which Xxe2x88x92 represents an anion of an aliphatic (preferably a saturated aliphatic) carboxylic acid or aromatic carboxylic acid, which is not substituted with a fluorine atom. Specific examples thereof include compounds of the specific examples of component (B) in which the fluorine atoms in the anion portions are substituted with hydrogen atoms.
The photo-acid generator used together with the compound of component (B) in the photoresist composition of the present invention is preferably selected from the compounds represented by formulae (PAG3), (PAG4) and (PAG7) and the compounds of component (Bxe2x80x2).
The compound of component (C) and/or component (Bxe2x80x2) may be used in a range of not more than 5% by weight, preferably not more than 4% by weight, based on the solid content of the positive photoresist composition of the present invention.
[3] (A) A resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution (Component (A)):
The component (A) is the indispensable component in the first composition of the present invention. The resin of component (A) having a group which decomposes with an acid and increases solubility in an alkaline developing solution (hereinafter also referred to as an xe2x80x9cacid-decomposable groupxe2x80x9d sometimes) is a resin having introduced an acid-decomposable group into the polymer main chain or side chain, or both the polymer main chain and side chain. A resin having an acid-decomposable group in the side chain is more preferred.
Preferred examples of the group decomposable with an acid include a group represented by xe2x80x94COOA0 and a group represented by xe2x80x94Oxe2x80x94B0. Examples of group containing such a group include a group represented by xe2x80x94R0xe2x80x94COOA0 and a group represented by xe2x80x94Arxe2x80x94Oxe2x80x94B0.
In the above formulae, A0 represents xe2x80x94C(R01)(R02)(R03), xe2x80x94Si(R01)(R02)(R03) or xe2x80x94C(R04)(R05)xe2x80x94Oxe2x80x94R06, and B0 represents xe2x80x94A0 or xe2x80x94COxe2x80x94Oxe2x80x94A0 (wherein R0, R01, R02, R03, R04, R05, R06 and Ar each has the same meaning as defined hereinafter).
Preferred examples of the acid-decomposable group include a silyl ether group, a cumyl ester group, an acetal group, a tetrahydropyranyl ether group, an enol ether group, an enol ester group, a tertiary alkyl ether group, a tertiary alkyl ester group and a tertiary alkylcarbonate group. More preferred examples thereof include a tertiary alkyl ester group, a tertiary alkylcarbonate group, a cumyl ester group, an acetal group and a tetrahydropyranyl ether group. An acetal group is particularly preferred.
A parent resin in the case wherein the acid-decomposable groups are bonded as a side chain is an alkali-soluble resin having an xe2x80x94OH group or a xe2x80x94COOH group, preferably an xe2x80x94R0xe2x80x94COOH group or an xe2x80x94Arxe2x80x94OH group, in the side chain. For instance, the alkali-soluble resins described below can be exemplified as such parent resins.
An alkali-dissolution rate of the alkali-soluble resin is preferably not less than 170 angstrom/sec, more preferably not less than 330 angstrom/sec, when measured in 0.261 N tetramethylammonium hydroxide (TMAH) at 23xc2x0 C.
In view of attaining a rectangular profile, an alkali-soluble resin which highly transmit a far ultraviolet ray or an excimer laser beam is preferred. Specifically, an alkali-soluble resin whose 1 xcexcm-thick film has transmittance at 248 nm of from 20% to 90% is preferred.
Especially preferred examples of the alkali-soluble resin from such a standpoint include poly(o-, m-, or p-hydroxystyrene), copolymer of hydroxystyrene, hydrogenated poly(hydroxystyrene), halogen- or alkyl-substituted poly(hydroxystyrene), partially O-alkylated or O-acylated poly (hydroxystyrene), styrene/hydroxystyrene copolymer, xcex1-methylstyrene/hydroxystyrene copolymer and hydrogenated novolak resin.
The resin having the acid-decomposable group for use in the present invention can be obtained by reacting an alkali-soluble resin with a precursor of the acid-decomposable group or by copolymerizing a monomer for forming an alkali-soluble resin and having the acid-decomposable group bonded thereto with any of various monomers, as described, for example, in European Patent 254,853, JP-A-2-25850, JP-A-3-223860 and JP-A-4-251259.
Specific examples of the resin having the acid-decomposable group for use in the present invention are set forth below, but the present invention should not be construed as being limited thereto.
p-tert-Butoxystyrene/p-hydroxystyrene copolymer
p-(tert-Butoxycarbonyloxy)styrene/p-hydroxystyrene copolymer
p-(tert-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene copolymer
4-(tert-Butoxycarbonylmethyloxy)-3-methylstyrene/4-hydroxy-3-methylstyrene copolymer
p-(tert-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene (10% hydrogenated) copolymer
m-(tert-Butoxycarbonylmethyloxy)styrene/m-hydroxystyrene copolymer
o-(tert-Butoxycarbonylmethyloxy)styrene/o-hydroxystyrene copolymer
p-(Cumyloxycarbonylmethyloxy)styrene/p-hydroxystyrene copolymer
Cumyl methacrylate/methyl methacrylate copolymer
4-tert-Butoxycarbonylstyrene/dimethyl maleate copolymer
Benzyl methacrylate/tetrahydropyranyl methacrylate copolymer
p-(tert-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene/styrene copolymer
p-tert-Butoxystyrene/p-hydroxystyrene/fumaronitrile copolymer
p-tert-Butoxystyrene/hydroxyethyl methacrylate copolymer
Styrene/N-(4-hydroxyphenyl)maleimide/N-(4-tert-butoxycarbonyloxyphenyl)maleimide copolymer
p-Hydroxystyrene/tert-butyl methacrylate copolymer
Styrene/p-hydroxystyrene/tert-butyl methacrylate copolymer
p-Hydroxystyrene/tert-butyl acrylate copolymer
Styrene/p-hydroxystyrene/tert-butyl acrylate copolymer
p-(tert-Butoxycarbonylmethyloxy)styrene/p-hydroxystyrene/N-methylmaleimide copolymer
tert-Butyl methacrylate/1-adamantylmethyl methacrylate copolymer
p-Hydroxystyrene/tert-butyl acrylate/p-acetoxystyrene copolymer
p-Hydroxystyrene/tert-butyl acrylate/p-(tert-butoxycarbonyloxy)styrene copolymer
p-Hydroxystyrene/tert-butyl acrylate/p-(tert-butoxycarbonylmethyloxy)styrene copolymer
Of the resins of component A having the acid-decomposable group, resins containing a repeating unit represented by formula (IV) and a repeating unit represented by formula (V) described above are preferred. The resulting photoresist composition has high resolution and change in its performance with the lapse of time from exposure to baking is further restrained.
The straight-chain, branched chain or cyclic alkyl group for L and Z in formula (IV) includes that having from 1 to 20 carbon atoms, for example, methyl ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl and dodecyl.
Preferred examples of the substituent for the alkyl group include an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, a nitro group, an acyl group, an acylamino group, a sulfonylamino group, an alkylthio group, an arylthio group and aralkylthio group. Specific examples of the substituted alkyl group include cyclohexylethyl, alkylcarbonyloxymethyl, alkylcarbonyloxyethyl, aryl-carbonyloxyethyl, aralkylcarbonyloxyethyl, alkyloxymethyl, aryloxymethyl, aralkyloxymethyl, alkyloxyethyl, aryloxyethyl, aralkyloxyethyl, alkylthiomethyl, arylthiomethyl, aralkylthiomethyl, alkylthioethyl, arylthioethyl and aralkylthioethyl. The alkyl group contained theses groups is not particularly limited and includes any of straight-chain, branched chain or cyclic alkyl group. Examples of such alkyl-substituted group include, for example, cyclohexylcarbonyloxyethyl, tert-butylcyclohexylcarbonyloxyethyl and n-butyl cyclohexylcarbonyloxyethyl. The aryl group contained theses groups is also not particularly limited and may be substituted. Examples of such aryl-substituted group include, for example, phenyloxyethyl and cyclohexylphenyloxyethyl. The aralkyl group contained theses groups is also not particularly limited. Examples of such aralkyl-substituted group include, for example, benzylcarbonyloxyethyl.
The aralkyl group for L and Z in formula (IV) includes that having from 7 to 15 carbon atoms, for example, a substituted or unsubstituted benzyl group and a substituted or unsubstituted phenethyl group. Preferred examples of the substituent for the aralkyl group include an alkoxy group, a hydroxy group, a halogen atom, a nitro group, an acyl group, an acylamino group, a sulfonylamino group, an alkylthio group, an arylthio group and aralkylthio group. Specific examples of the substituted aralkyl group include alkoxybenzyl, hydroxybenzyl and phenylthiophenetyl.
It is preferred that Z represents a substituted alkyl group or a substituted aralkyl group, since further improvement in edge roughness is recognized. Preferred examples of the substituent for the alkyl group include a cyclic alkyl group, an aryloxyl group, an alkylcarboxy group, an arylcarboxy group and an aralkylcarboxy group. Preferred examples of the substituent for the aralkyl group include an alkyl group, a cyclic alkyl group and a hydroxy group.
The 5-membered or 6-membered ring formed by being combined with Z and L each other includes, for example, a tetrahydropyran ring and a tetrahydrofuran ring.
A molar ratio of the repeating unit represented by formula (IV)/the repeating unit represented by formula (V) present in the resin is preferably from 1/99 to 60/40, more preferably from 5/95 to 50/50 and still more preferably from 10/90 to 40/60.
The resin containing the repeating unit represented by formula (IV) and the repeating unit represented by formula (V) described above may further contain a repeating unit derived from other monomer(s).
Examples of the other monomer include a hydrogenated hydroxystyrene; a halogen-, alkoxy- or alkyl-substituted hydroxystyrene; styrene; a halogen-, alkoxy- acyloxy- or alkyl-substituted styrene; maleic anhydride; an acrylic acid derivative; a methacrylic acid derivative; and an N-substituted maleimide, but the present invention should not be construed as being limited thereto.
A molar ratio of the repeating unit represented by formula (IV) and the repeating unit represented by formula (V)/the repeating unit of other monomer, i.e., [(IV)+(V)]/[other monomer]present in the resin is ordinarily from 100/0 to 50/50, preferably from 100/0 to 60/40 and more preferably from 100/0 to 70/30.
Specific examples of the resin containing the repeating unit represented by formula (IV) and the repeating unit represented by formula (V) and other resin which can be used in the present invention are set forth below, bur the present invention should not be construed as being limited thereto.
In the above-described formulae, Me represents a methyl group, Et represents an ethyl group, n-Bu represents a n-butyl group, iso-Bu represents an isobutyl group and t-Bu represents a tert-butyl group.
In case of using an acetal group as the acid-decomposable group, crosslinking portions connected with polyfunctional acetal groups may be introduced into the polymer main chain by means of adding a polyhydroxy compound in the preparation step thereof in order to control an alkali-dissolution rate and to improve heat-resistance. The amount of the polyhydroxy compound added is preferably from 0.01 to 5 mol %, more preferably from 0.05 to 4 mol %, based on the content of hydroxy group in the resin. The polyhydroxy compound to be used has phenolic hydroxy groups or alcoholic hydroxy groups in an amount of 2 to 6, preferably from 2 to 4 and more preferably from 2 to 3.
Specific examples of the polyhydroxy compound are set forth below, bur the present invention should not be construed as being limited thereto.
The weight average molecular weight (Mw) of the resin of component (A) having the acid-decomposable group is preferably in a range of from 2,000 to 300,000. If it is less than 2,000, decrease in a film thickness of the unexposed area during development is large and on the other hand, if it exceeds 300,000, a dissolution rate of the resin per se to alkali decreases, resulting in lowering sensitivity. The weight average molecular weight is measured by gel permeation chromatography and defined in terms of polystyrene.
Two or more of the resins of component (A) having the acid-decomposable group may be used in the photoresist composition of the present invention.
The amount of the resin of component (A) is ordinarily from 40 to 99% by weight, preferably from 60 to 98% by weight, based on the solid content of the first composition of the present invention.
[4] (D) A compound having a molecular weight of not more than 3,000 which decomposes by the action of an acid to increase solubility in an alkaline developing solution (Component (D)):
The component (D) is the indispensable component in the second composition of the present invention, and is incorporated into the first component, if desired. The compound of component (D) is a low molecular weight compound which has a group decomposable with an acid, whose solubility in an alkaline developing solution is increased by the action of an acid, and which has a molecular weight of not more than 3,000, preferably from 200 to 2,000, and more preferably from 300 to 1,500. The compound of component (D) functions as a compound for inhibiting dissolution of the unexposed portion in the alkaline developing solution. The term xe2x80x9cacid-decomposable dissolution-inhibiting compoundxe2x80x9d has the same meaning as the compound of component (D) hereinafter.
The compound of component (D), i.e., acid-decomposable dissolution-inhibiting compound is preferably a compound containing at least two acid-decomposable groups in its structure wherein at least 8 connecting atoms other than acid-decomposable group are interposed between the acid-decomposable groups which are separated from each other at the greatest distance.
Preferred examples of the acid-decomposable dissolution-inhibiting compound include (a) a compound containing at least two acid-decomposable groups in its structure wherein at least 10, preferably at least 11, more preferably at least 12 connecting atoms other than acid-decomposable group are interposed between the acid-decomposable groups which are separated from each other at the greatest distance, and (b) a compound containing at least three acid-decomposable groups in its structure wherein at least 9, preferably at least 10, more preferably at least 11 connecting atoms other than acid-decomposable group are interposed between the acid-decomposable groups which are separated from each other at the greatest distance.
The upper limit of the number of the above-described connecting atoms is preferably 50, more preferably 30.
When the acid-decomposable dissolution-inhibiting compound contains three or more, preferably four or more acid-decomposable groups, even two acid-decomposable groups, its dissolution-inhibiting function to the alkali-soluble resin is remarkably enhanced as far as these acid-decomposable groups are separated from each other at the predetermined distance.
The distance between the acid-decomposable groups is represented by the number of connecting atoms interposed therebetween excluding the acid-decomposable groups. For, instance, in the case of compounds (1) and (2) described below, the distance between the acid-decomposable groups is four connecting atoms, respectively. In the case of compound (3) described below, the distance between the acid-decomposable groups is 12 connecting atoms.
Acid-decomposable group: xe2x80x94COOxe2x80x94A0 or xe2x80x94Oxe2x80x94B0
Further, the acid-decomposable dissolution-inhibiting compound may have a plurality of acid-decomposable groups on one benzene ring. Preferably, it is a compound formed by a skeleton having one acid-decomposable group on one benzene ring.
A group containing the acid-decomposable group, i.e., a group containing xe2x80x94COOxe2x80x94A0 group or xe2x80x94Oxe2x80x94B0 group is preferably a group represented by formula xe2x80x94R0xe2x80x94COOxe2x80x94A0 or xe2x80x94Arxe2x80x94Oxe2x80x94B0.
In the above formulae, A0 represents xe2x80x94C(R01)(R02)(R03), xe2x80x94Si(R01)(R02)(R03) or xe2x80x94C(R04)(R05)xe2x80x94Oxe2x80x94R06, and B0 represents xe2x80x94A0 or xe2x80x94COxe2x80x94Oxe2x80x94A0.
R01, R02, R03, R04 and R05, which may be the same or different, each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group, and R06 represents an alkyl group or an aryl group. However, at least two of R01 to R03 are not hydrogen atoms; and two of R01 to R03 may be bonded to each other to form a ring, and two of R04 to R06 may be bonded to each other to form a ring. R0 represents an aliphatic or aromatic hydrocarbon group having a valence of 2 or higher, which may be substituted, and xe2x80x94Arxe2x80x94 represents a monocyclic or polycyclic aromatic group having a valence of 2 or higher, which may be substituted.
Preferred examples of the alkyl group include those having from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, n-butyl, sec-butyl and tent-butyl. Preferred examples of the cycloalkyl group include those having from 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclohexyl and adamantly.
Preferred examples of the alkenyl group include those having from 2 to 4 carbon atoms, such as vinyl, propenyl, allyl and butenyl.
Preferred examples of the aryl group include those having from 6 to 14 carbon atoms, such as phenyl, xylyl, tolyl, cumenyl, naphthyl and anthracenyl.
Examples of the substituent include a hydroxy group, a halogen atom (e.g., fluorine, chlorine, bromine and iodine), a nitro group, a cyano group, the above-described alkyl group, an alkoxy group such as methoxy, ethoxy, hydroxyethoxy, propoxy, hydroxypropoxy, n-butoxy, isobutoxy, sec-butoxy and tert-butoxy, an alkoxycarbonyl group such as methoxycarbonyl and ethoxycarbonyl, an aralkyl group such as benzyl, phenethyl and cumyl, an aralkyloxy group, an acyl group such as formyl, acetyl, butyryl, benzoyl, cyanamyl and valeryl, an acyloxy group such as butyryloxy, the above-described alkenyl group, an alkenyloxy group such as vinyloxy, propenyloxy, allyloxy and butenyloxy, the above-described aryl group, an aryloxy group such as phenoxy, and an aryloxycarbonyl group such as benzoyloxy.
Preferred examples of the acid-decomposable group include a silyl ether group, a cumyl ester group, an acetal group, a tetrahydropyranyl ether group, an enol ether group, an enol ester group, a tertiary alkyl ether group, a tertiary alkyl ester group and a tertiary alkylcarbonate group. More preferred examples thereof include a tertiary alkyl ester group, a tertiary alkylcarbonate group, a cumyl ester group and a tetrahydropyranyl ether group.
The compound of component (D) includes compounds protected by connecting a part or all of phenolic hydroxy groups in polyhydroxy compounds as described, for example, in JP-A-1-289946, JP-A-1-289947, JP-A-2-2560, JP-A-3-128959, JP-A-3-158855, JP-A-3-179353, JP-A-3-191351, JP-A-3-200251, JP-A-3-200252, JP-A-3-200253, JP-A-3-200254, JP-A-3-200255, JP-A-3-259149, JP-A-3-279958, JP-A-3-279959, JP-A-4-1650, JP-A-4-1651, JP-A-4-11260, JP-A-4-12356, JP-A-4-12357, JP-A-4-271349, JP-A-5-45869, JP-A-5-158233, JP-A-5-224409, JP-A-5-257275, JP-A-5-297581, JP-A-5-297583, JP-A-5-303197, JP-A-5-303200, JP-A-5-341510, via the above-described group of xe2x80x94R0xe2x80x94COOxe2x80x94A0 or xe2x80x94B0. More preferred compounds are those formed from the polyhydroxy compounds as described in JP-A-1-289946, JP-A-3-128959, JP-A-3-158855, JP-A-3-179353, JP-A-3-200251, JP-A-3-200252, JP-A-3-200255, JP-A-3-259149, JP-A-3-279958, JP-A-4-1650, JP-A-4-11260, JP-A-4-12356, JP-A-4-12357, JP-A-5-224409, JP-A-5-297581, JP-A-5-297583, JP-A-5-303197, JP-A-5-303200, JP-A-5-34510.
Specific examples of the preferred compound skeleton for the compound of component (D) are set forth below, but the present invention should not be construed as being limited thereto.
In the above-described formulae of Compounds (1) to (44), R represents a hydrogen atom, xe2x80x94CH2COOC(CH3)2C6H5,xe2x80x94CH2COOC4C9-tert, xe2x80x94COOC4C9-tert or
with the proviso that at least two or three, depending on the structure, of R""s are groups other than a hydrogen atom and R""s may be the same or different.
In the first composition, the content of the component (D) is preferably from 3 to 45% by weight, more preferably from 5 to 30% by weight, and still more preferably from 10 to 20% by weight, based on the solid content of the first composition.
The content of the component (D) in the second composition is same as that in the first composition.
[5] (E) An alkali-soluble resin (Component (E)):
The alkali-soluble resin of component (E) is the indispensable component in the second composition of the present invention. The alkali-soluble resin is a component which may added to the first composition of the present invention. The alkali-soluble resin of component (E) is a resin which is water-insoluble but soluble in an alkaline developing solution and used for controlling the solubility of the second composition in alkali. The alkali-soluble resin dose not substantially have the acid-decomposable group.
Examples of the resin of component (E) include novolak resin, hydrogenated novolak resin, acetone-pyrogallol resin, o-polyhydroxystyrene, m-polyhydroxystyrene, p-polyhydroxystyrene, hydrogenated polyhydroxystyrene, halogen- or alkyl-substituted polyhydroxystyrene, hydroxystyrene/N-substituted maleimide copolymer, o/p- or m/p-hydroxystyrene copolymer, partially O-alkylated product of hydroxyl group in polyhydroxystyrene (e.g., 5 to 30 mol % O-methylated product, O-(1-methoxy)ethylated product, O-(1-ethoxy)ethylated product, O-2-tetrahydropyranylated product, O-(tert-butoxycarbonyl)methylated product), partially O-acylated product of hydroxyl group in polyhydroxystyrene (e.g., 5 to 30 mol % O-acetylated product, O-(tert-butoxy)carbonylated product), styrene/maleic anhydride copolymer, styrene/hydroxystyrene copolymer, xcex1-methylstyrene/hydroxystyrene copolymer, carboxyl group-containing methacrylic resin and derivative thereof, and polyvinyl alcohol derivative. However, the present invention should not be construed as being limited thereto.
Particularly preferred examples of the alkali-soluble resin include novolak resin, o-polyhydroxystyrene, m-polyhydroxystyrene, p-polyhydroxystyrene and copolymer thereof, alkyl-substituted polyhydroxystyrene, partially O-alkylated product of polyhydroxystyrene, partially O-acylated product of polyhydroxystyrene, styrene/hydroxystyrene copolymer, and xcex1-methylstyrene/hydroxystyrene copolymer. The above-described novolak resin can be obtained by subjecting a specific monomer as a main component to an addition condensation reaction with an aldehyde in the presence of an acid catalyst.
The weight average molecular weight of the novolak resin is preferably in a range of from 1,000 to 30,000. If the weight average molecular weight thereof is lower than 1,000, decrease in a film thickness of the unexposed area during development is large. On the other hand, if the weight average molecular weight thereof exceeds 30,000, a developing rate decreases. A particularly preferred range of the weight average molecular weight of the novolak resin is from 2,000 to 20,000.
The poly(hydroxystyrene)s and derivatives and copolymers thereof described above other than the novolak resin each has a weight average molecular weight of ordinarily not less than 2,000, preferably from 5,000 to 200,000, more preferably from 8,000 to 100,000. Further, from a standpoint of improvement in heat resistance of the resist film, the weight average molecular weight is preferably not less than 10,000.
The weight average molecular weight used herein means that measured by gel permeation chromatography and defined in terms of polystyrene.
In the composition of the present invention, the alkali-soluble resins may be used as a mixture of two or more thereof.
The content of the alkali-soluble resin is preferably from 40 to 97% by weight, more preferably from 60 to 90% by weight, based on the solid content of the second composition.
[6] (F) A nitrogen-containing basic compound (component (F)):
The nitrogen-containing basic compound of component (F) which is used in the positive photoresist composition of the present invention is preferably a compound which has basicity stronger than phenol. Among others, the nitrogen-containing basic compounds having a structure represented by formulae (A), (B), (C), (D) and (E) shown below are preferred. By the use of the nitrogen-containing basic compound, change in performance of the photoresist composition with the lapse of time from exposure to post-baking is restrained.
wherein R250, R251 and R252, which may be the same or different, each represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, an aminoalkyl group having from 1 to 6 carbon atoms, a hydroxyalkyl group having from 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having from 6 to 20 carbons atoms, or R251 and R252 may be combined with each other to form a ring;
wherein R253, R254, R255 and R256, which may be the same or different, each represents an alkyl group having from 1 to 6 carbon atoms.
Preferred examples of the nitrogen-containing basic compound include a substituted or unsubstituted guanidine, a substituted or unsubstituted aminopyridine, a substituted or unsubstituted aminoalkylpyridine, a substituted or unsubstituted aminopyrrolidine, a substituted or unsubstituted indazole, a substituted or unsubstituted pyrazole, a substituted or unsubstituted pyrazine, a substituted or unsubstituted pyrimidine, a substituted or unsubstituted purine, a substituted or unsubstituted imidazoline, a substituted or unsubstituted pyrazoline, a substituted or unsubstituted piperazine, a substituted or unsubstituted aminomorpholine, a substituted or unsubstituted aminoalkylmorpholine, a mono- di- or tri-amine, a substituted or unsubstituted aniline, a substituted or unsubstituted piperidine and a mono- or diethanolamine. Examples of the substituent includes preferably an amino group, an aminoalkyl group, an alkylamino group, an aminoaryl group, an arylamino group, an alkyl group, an alkoxy group, an acyl group, an acyloxy group, an aryl group, an aryloxy group, a nitro group, a hydroxyl group and a cyano group.
More preferred examples of the compound include guanidine, 1,1-dimethylguanidine, 1,1,3,3-tetramethylguanidine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-dimethylaminopyridine, 4-dimethylaminopyridine, 2-diethylaminopyridine, 2-(aminomethyl)pyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-6-methylpyridine, 3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine, piperazine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)piperidine, 4-amino-2,2,6,6-tetramethylpiperidine, 4-piperidinopiperidine, 2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine, pyrazole, 3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine, 2-(aminomethyl)-5-methylpyrazine, pyrimidine, 2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine, N-(2-aminoethyl)morpholine, 1,5-diazabicyclo[4,3,0]nona-5-ene, 1,8-diazabicyclo[5,4,0]undeca-7-ene, 2,4,5-triphenylimidazole, tri(n-butyl)amine, tri(n-octyl)amine, N-phenyldiethanolamine, N-hydroxyethylpiperidine, 2,6-diisopropylamine, N-cyclohexyl-Nxe2x80x2-morpholinoethylthiourea and N-hydroxyethylmorpholine. However, the present invention should not be construed as being limited thereto.
Of these compounds, 1,5-diazabicyclo[4,3,0]nona-5-ene, 1,8-diazabicyclo[5,4,0]undeca-7-ene, 2,4,5-triphenylimidazole, tri(n-butyl)amine, tri(n-octyl)amine, N-phenyldiethanolamine, N-hydroxyethylpiperidine, 2,6-diisopropylamine, N-cyclohexyl-Nxe2x80x2-morpholinoethylthiourea and N-hydroxyethylmorpholine are particularly preferred.
The nitrogen-containing basic compounds are used individually or in combination of two or more thereof.
The amount of the nitrogen-containing basic compound used is ordinarily from 0.001 to 10% by weight, preferably from 0.01 to 5% by weight, based on the solid content of the photoresist composition. If the amount used is less than 0.001% by weight, the effect owing to the addition of the nitrogen-containing basic compound can not be obtained, whereas if it exceeds 10% by weight, reduction in sensitivity or deterioration in developing property of the unexposed area is liable to occur.
[7] (G) A fluorine-base or silicon-base surface active agent (Component (G)):
It is preferred that the photoresist composition of the present invention contains Component (G). The surface active agent of component (G) is selected from a fluorine-base surface active agent, a silicon-base surface active agent and a surface active agent having both a fluorine atom and a silicon.
The positive photoresist composition containing the fluorine-base or silicon-base surface active agent according to the present invention is excellent in sensitivity, resolution, adhesion property to a substrate and dry etching resistivity when an exposure light source having a wavelength of 250 nm or less, particularly 220 nm or less is used. Also, the occurrence of particles during the preservation of the resist composition is restrained. Further, a resist pattern with less development defect and scum is obtained.
Examples of the fluorine-base or silicon-base surface active agent include those described, for example, in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432 and JP-A-9-5988. Commercially available surface active agents are also employed as they are.
Examples of commercially available surface active agents which can be used include fluorine-base surface active agents and silicon-base surface active agents, for example, F-Top EF301 and EF303 (manufactured by Shin Akita Chemical Co., Ltd.), Florard FC430 and FC431 (manufactured by Sumitomo 3M Ltd.), Megafac F171, F173, F176, F189 and R08 (manufactured by Dainippon Ink and Chemicals, Inc.), Serflon S-382, SC101, SC102, SC103, SC104, SC105 and SC106 (manufactured by Asahi Glass Co., Ltd.), and TROYSOL S-366 (manufactured by TROY CHEMICAL CO., LTD.). Also, polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) is employed as the silicon-base surface active agent.
The amount of the fluorine-base or silicon-base surface active agent added is ordinarily from 0.001 to 2% by weight, preferably from 0.01 to 1% by weight, based on the solid content of the photoresist composition of the present invention. The surface active agents may be used individually or in combination of two or more thereof.
[8] Other components usable in the photoresisit composition of the present invention:
The positive photoresist composition of the present invention may further contain, if desired, a dye, a pigment, a plasticizer, a surface active agent other than the fluorine-base or silicon-base surface active agent described above, a photosensitizer, a compound having two or more phenolic OH groups, which accelerates the solubility in a developing solution, and the like.
The compound containing two or more phenolic OH groups, which can be used in the present invention, is preferably a phenol compound having a molecular weight of not more than 1,000. The phenol compound needs to contain at least two phenolic hydroxyl groups in its molecule. However, if the number of phenolic hydroxyl groups contained in the phenol compound exceeds 10, the desired effect for improving development latitude is lost. Further, if the ratio of phenolic hydroxyl group to aromatic ring is less than 0.5, the dependence on film thickness becomes large and the development latitude tends to narrow. On the other hand, it is not preferred that the ratio exceeds 1.4, since stability of the resulting photoresist composition deteriorates and it is difficult to obtain high resolution and good dependence on film thickness.
The amount of the phenol compound added is preferably from 2 to 50% by weight, more preferably from 5 to 30% by weight, based on the weight of the alkali-soluble resin. If the amount of the phenol compound added exceeds 50% by weight, development residue increases adversely and a new problem disadvantageously arises such that the pattern deforms during the development.
The above-described phenol compound having a molecular weight of not more than 1,000 can be easily synthesized by one skilled in the art making reference to the methods described, for example, in JP-A-4-122938, JP-A-2-28531, U.S. Pat. No. 4,916,210 and European Patent 219,294.
Specific examples of the phenol compound are set forth below, however, the compound which can be used in the present invention should not be construed as being limited thereto.
Resorcinol, phloroglucinol, 2,3,4-trihydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, 2,3,4,3xe2x80x2,4xe2x80x2,5xe2x80x2-hexahydroxybenzophenone, acetone-pyrogallol condensed resin, phloroglucoside, 2,4,2xe2x80x2,4xe2x80x2-biphenyltetrol, 4,4xe2x80x2-thiobis(1,3-dihydroxy)benzene, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxydiphenyl ether, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxydiphenyl sulfoxide, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxydiphenylsulfone, tris(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4-(xcex1-methylbenzylidene)bisphenol, xcex1,xcex1xe2x80x2,xcex1xe2x80x3-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, xcex1,xcex1xe2x80x2,xcex1xe2x80x3-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene, 1,2,2-tris(hydroxyphenyl)propane, 1,1,2-tris(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2,5,5-tetrakis(4-hydroxyphenyl)hexane, 1,2-tetrakis(4-hydroxyphenyl)ethane, 1,1,3-tris(hydroxyphenyl)butane and para[xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetrakis (4-hydroxyphenyl)]xylene.
Each of the components contained in the photoresist composition of the present invention are described above.
 less than Preparation of the positive photoresist composition and use thereof greater than
A method for the preparation of positive photoresist composition and a method for the use thereof will be described below.
The photoresist composition of the present invention is dissolved in a solvent which can dissolve the above-described respective components, and then coated on a support. Examples of the solvent used includes preferably ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, xcex3-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and tetrahydrofuran. The solvents may be used individually or in combination of two or more thereof.
Of the solvents described above, 2-heptanone, xcex3-butyrolactone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, N-methylpyrrolidone and tetrahydrofuran are more preferably used.
It is preferred to add the fluorine-base or silicon-base surface active agent of component (G) described above to the solvent.
Further, a surface active agent other than the fluorine-base or silicon-base surface active agent of component (G) may be added. Specific examples of such a surface active agent include a nonionic surface active agent, for example, a polyoxyethylene alkyl ether such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether and polyoxyethylene oleyl ether, a polyoxyethylene alkylaryl ether such as polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether, a polyoxyethylene/polyoxypropylene block copolymer, a sorbitan fatty acid ester such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate and sorbitan tristearate, and a polyoxyethylene sorbitan fatty acid ester such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate and polyoxyethylene sorbitan tristearate, and an acrylic or methacrylic (co)polymer (Polyflow No. 75 and NO. 95 manufactured by Kyoei Yusi Kagaku Kogyo Co., Ltd.).
The amount of the surface active agent added is ordinarily not more than 2 parts by weight, preferably not more than 1 part by weight, based on 100 parts by weight of the solid content of the photoresist composition of the present invention.
The above-described photoresist composition is coated on a substrate (e.g., silicon/silicon dioxide coating) for use in the production of a precision integrated circuit element by an appropriate coating means such as a spinner or coater, exposed through a predetermined mask, baked and developed to thereby obtain a good resist pattern.
A developing solution which can be used for the photoresist composition according to the present invention is an alkaline aqueous solution of an inorganic alkali such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate and aqueous ammonia, a primary amine such as ethylamine and n-propylamine, a secondary amine such as diethylamine and di-n-butylamine, a tertiary amine such as triethylamine and methyldiethylamine, an alcohol amine such as dimethylethanolamine and triethanolamine, a quaternary ammonium salt such as tetramethylammonium hydroxide and tetraethylammonium hydroxide, and a cyclic amine such as pyrrole and piperidine.
To the alkaline aqueous solution, an appropriate amount of an alcohol or surface active agent may be added.
The positive photoresist composition of the present invention is improved in resolution and process allowance such as exposure margin and depth of focus in a lithographic technology using a light source having a short wavelength capable of conducting the ultra fine fabrication and a chemical amplification-type positive photoresist. Further, it exhibits the excellent performance when an electron beam is used as a light source for exposure.


A message transmission and page processing scheme for a hypermedia document processing system, in which the source information which contains a source server identifier for identifying a source server in the system, a source page identifier for identifying a source page in the system, a request page identifier for identifying the request page in the system, and a request target server identifier for identifying a request target server in the system, is transmitted from a client device to a server device either directly or through a relay server device. A prescribed processing according to the source information is then carried out at the server device. In a case of using the relay server device, the relay server device can counts a number of source information, or separate the source information from a request message transmitted from the client device, or generate the source information from the page message from the server device and the request message from the client device.

1. Field of the Invention
The present invention relates to a message transmission scheme and a page processing scheme to be used in a system for processing a hypermedia document formed by electronic text and links pointing to that text, and a client device, a server device, and a relay server device for realizing these message transmission scheme and page processing scheme.
2. Description of the Background Art
The hypermedia is a technique which provides means for flexibly accessing multifarious information by relating multimedia data, including such data as text, video, static image, figure, and speech data, through links. A hypermedia document is a multimedia document provided by using this hypermedia technique.
A device which stores and provides a hypermedia document is called server, while a device for acquiring and displaying a hypermedia document is called client.
Now, with reference to FIG. 1, a principle of the hypermedia technique will be described.
FIG. 1 shows three "pages" (page-1 19-1, page-2 19-2 and page-3 19-3) where a "page" is a unit of information provided by the hypermedia technique. Within each page, various information such as text and images are described, and in addition, an "anchor" (such as anchor-1 19-4 and anchor-2 19-5) for pointing to a related information page is embedded. For this reason, by using the anchor-1, for example, it is possible to acquire the page-2 from the page-1.
In order to comprehend a relation, it is often regarded as having a "link" (such as link-A 19-6 and link-B 19-7) which is virtually set up from the anchor-1 to the page-2. A user can acquire the relation information of the page-2 by tracing the link-A from the anchor-1 in the page-1. In addition, a user can also acquire the page-3 by tracing the link-B from the anchor-2 in the page-2. Here, a uniquely defined identifier is used for each page, so that a page can be specified from an anchor without a failure. A processing to search information by tracing links in this manner is called navigation.
As a page identifier for identifying a page and a server identifier for identifying a server which stores that page, the following two schemes are possible.
(1) A page identifier is defined as an information which can identify that page within a network. In this case, a page identifier can be given by a host name which can identify a server which stores that page, and a file, name or (directory name+file name) of that page, for example. PA1 (2) A page identifier is defined as an information which can identify that page within a server which stores that page. Also, a server identifier is defined as an information which can identify that server within a network. Consequently, each page can be identified within a network by a pair of a server identifier and a page identifier. PA1 transmitting from said one client device a request message requesting a second page of the hypermedia documents to be referred from the first page to a request target server which stores the second page, the request message including a request page information which contains a request page identifier for identifying the second page in the system and a request target server identifier for identifying the request target server in the system; transferring at the relay server device a page message for the first page from said one server device to said one client device, the page message including a source page information which contains a source server identifier for identifying said one server device in the system and a source page identifier for identifying the first page in the system; transferring at the relay server device the request message from said one client device to said one server device; generating at the relay server device a source information message including a source information which contains the source server identifier and the source page identifier obtained from the page message, and the request page identifier and the request target server identifier obtained from the request message; transmitting the source information message from the relay server device to said one server device; receiving the source information message from the relay server device at said one server device; and carrying out a prescribed processing according to the source information in the source information message at said one server device.
In the following description, a page identifier and a server identifier as defined in the above scheme (2) will be used, but (server identifier+page identifier) appearing in the following description can be considered as an equivalent of a page identifier in the above scheme (1).
Note that it is also possible to consider a case in which a server identifier alone is set up as a link pointed by an anchor while a default page identifier is set up at the server side, but in such a case, a page identifier corresponding to an anchor is set to be null.
Now, some terminologies which will be used throughout the present specification will be defined.
A "source page" is defined as a page which contains an anchor for generating a page request.
A "source server" is defined as a server which stores the source page.
A "source information" is defined as an information which contains at least an identifier of the source page and an identifier of the source server.
A "request page" is defined as a page which is requested to be acquired and displayed next.
A "request page information" is defined as an information which contains an identifier of the server which stores the request page, and an identifier of the request page.
Now, with reference to FIG. 2, examples of a conventional server and a conventional client will be described.
A server 1-1 has a reception unit 1-2 for receiving a page request (request message), a page memory unit 1-3 for storing hypermedia documents, a request processing unit 1-4 for reading out a necessary page from the page memory unit 1-3 according to a received page request, and a transmission unit 1-5 for transmitting a read out page to a request source.
A client 1-11 has a reception unit 1-12 for receiving a page, a page interpretation unit 1-13 for interpreting a received page in order to display it while outputting an information on a link target page which is requested by an anchor selection command in a currently displayed page, a display unit 1-14 for displaying an interpreted page, an input unit 1-15 for receiving a page request from a user given by an anchor selection command, a request generation unit 1-16 for generating a page acquisition request containing an identifier of a server which stores a request page and an identifier of a request page according to a command from the input unit 1-15 and an information from the page interpretation unit 1-13, a transmission unit 1-17 for transmitting a request message produced from a page acquisition request and a source information, and a source information generation unit 1-18 for producing a source information containing an identifier of a source server which acquired a currently displayed page and an identifier of a current displayed page at a time of requesting a new page.
Note that, in general, as shown in FIG. 2, the server 1-1 and the client 1-11 are connected through a network 1-19, but there may be a case in which functions of both the server 1-1 and the client 1-11 are realized on an identical computer, as in a case of handling hypermedia documents provided on CD-ROM.
Next, with reference to FIG. 3, the operation for requesting a page and generating a source information in a system formed by the conventional server 1-1 and client 1-11 will be described.
At the client 1-11, while a page-A acquired from some server is currently displayed (2-1), when a command (2-2) for tracing an anchor-C on the page-A is entered from the input unit 1-15, the request generation unit 1-16 receives an information (2-3) on a page-B corresponding to the anchor-C from the page interpretation unit 1-13, and produces a page request (2-4).
On the other hand, the source information generation unit 1-18 receives an information (2-5) on a currently displayed page from the page interpretation unit 1-13, and produces a source information (2-6).
Then, the transmission unit 1-17 produces a request message (2-7) from the page request (2-4) and the source information (2-6), and transmits it through the network 1-19 to the server 1-1 which stores a request page.
At the server 1-1 which received this request message, a page request information (2-8) is sent to the request processing unit 1-4, and the page-B (2-9) is read out from the page memory unit 1-3 and transferred to the client 1-11.
When the page-B is successfully acquired from the server 1-1, after a prescribed processing such as interpreting and displaying of the acquired page is carried out, the client 1-11 is set in a state capable of receiving a next page request.
Now, in this server-client system, the source information contained in the received message (2-7) is an information concerning a page which is stored on the other server in general, and this source information has not been utilized effectively in the conventional system.
The prior art regarding the source information includes a reference field defined in Hypertext Transfer Protocol-HTTP/1.0 for specifying link relations in the World Wide Web, which is the worldwide distributed hypermedia.
Note however that this information is useful for a server but useless for a client, and defined as an option which may or may not be sent by a client side. Hypertext Transfer Protocol-HTTP/1.0 mentioned above is disclosed as the Internet Draft as of July, 1995.
Conventionally, the source information can be sent from the client to the request target server by attaching it to the page request, but this source information has not been transmitted to the source server which stores the source page. For this reason, it has been impossible for the source server to learn about a utilization frequency of an anchor in a page.
In addition, in a case where a reference target page is deleted, when an anchor which is referring to that page is traced, it causes an error as it is impossible to reach to that page within a prescribed period of time, so that there is a need to correct this anchor to point to a correct information. However, in the conventional system, no means for enabling the source server side to learn an occurrence of an error at the client has been provided.
In addition, as defined in HTTP/1.0 mentioned above, there is no guarantee that the source information is always produced by every client.
Thus, conventionally, there is no means for enabling the source server to learn the fact of a utilization of an anchor in each page, its utilization frequency, and its utilization result.

Message transmission scheme and page processing scheme for hypermedia document processing system


A fuel cell system and method in which the fuel cell system receives and an input oxidant gas and an input fuel gas, and in which a fuel processing assembly is provided and is adapted to at least humidify the input fuel gas which is to be supplied to the anode of the fuel cell of the system whose cathode receives the oxidant input gas via an anode oxidizing assembly which is adapted to couple the output of the anode of the fuel cell to the inlet of the cathode of the fuel cell during normal operation, shutdown and restart of the fuel cell system, and in which a control assembly is further provided and is adapted to respond to shutdown of the fuel cell system during which input fuel gas and input oxidant gas cease to be received by the fuel cell system, the control assembly being further adapted to, when the fuel cell system is shut down: control the fuel cell system so as to enable a purging gas to be able to flow through the fuel processing assembly to remove humidified fuel gas from the processing assembly and to enable a purging gas to be able to flow through the anode of the fuel cell.

This invention relates to fuel cell systems and, in particular, to control assemblies for controlling fuel cell systems during shutdown and restart.
A fuel cell is a device, which directly converts chemical energy stored in hydrocarbon fuel into electrical energy by means of an electrochemical reaction. Generally, a fuel cell comprises an anode and a cathode separated by an electrolyte, which serves to conduct electrically charged ions. In order to produce a useful power level, a number of individual fuel cells are stacked in series with an electrically conductive separator plate between each cell.
A molten carbonate fuel cell ("MCFC") system operates by passing a reactant fuel gas through the anode of the fuel cell of the fuel cell system, while an oxidizing gas is passed through the cathode of the fuel cell of the fuel cell system. The fuel supplied to the MCFC system is typically a hydrocarbon fuel which needs to be humidified, usually by adding vaporized water or steam, before the fuel enters the anode of the fuel cell. During MCFC operation, the oxidizing gas keeps the cathode of the fuel cell in an oxidizing atmosphere, while the humidified fuel gas keeps the anode of the fuel cell in a reducing atmosphere.
When the MCFC system is shut down, i.e., when the fuel cell is at its operating temperature and the fuel and oxidant gases are no longer supplied to the system, a number of things must occur to protect the system. First, the oxidizing atmosphere must be maintained in the cathode of the fuel cell and the reducing atmosphere must be maintained in the anode of the fuel cell. Second, the humidified fuel present in the fuel lines of the MCFC system needs to be purged in order to prevent condensation, possible Nickel Carbonyl formation and damage to the catalysts in the fuel cell by liquid water.
When the MCFC system is restarted, i.e., when the flows are reestablished after a shutdown, again certain conditions must be present to ensure continued system operation. During restart, the oxidant flow is established before initiation of the fuel flow. Thus, a reducing atmosphere needs to be maintained in the anode of the fuel cell during the time when the regular fuel flow is not available to prevent oxidation of the anode. Additionally, during this time, carbon dioxide needs to be supplied both to the anode gas stream and to the cathode of the fuel cell. This is needed in order to prevent decomposition of the fuel cell electrolyte as well as to prevent fuel cell matrix particle growth at the matrix anode interface.
A number of techniques for controlling a fuel cell system during shutdown have been disclosed. Japanese Patent Application Publication No. 04004570 discloses a fuel cell system in which a standby gas containing mainly hydrogen is supplied to the anode of the fuel cell during a shutdown of the system and when the system is at its normal operating temperature. This prevents oxidation of the anode. Another Japanese Patent Application Publication No. 04324253 describes a fuel cell system having a standby gas used to prevent oxidation of the anode of the fuel cell during shutdown of the system. In this case the standby gas is prepared by mixing a reducing gas with nitrogen.
Japanese Patent Application Publication No. 10289724 discloses another method used during shutdown of a fuel cell system. In this method, an inerting gas made of nitrogen or argon and containing between 1 and 10% carbon dioxide is supplied to the fuel cell cathode to reduce growth of LiAlO2 particles in the electrolyte plate. European Patent Application Publication No. EP01481436 refers to another inerting procedure used during shutdown of a fuel cell system in which water vapor is supplied to the fuel cell anode and an electrolysis reaction is effected by applying an external potential to the fuel cell. Finally, Japanese Patent Application Publication No.10032013 describes a purging method used to control a fuel cell system after a shut down in which purging is accomplished by re-circulating the anode and cathode streams separately and inerting the streams separately.
The systems discussed above, however, do not provide an overall system capable of realizing the conditions described previously as required by a MCFC system during shutdown and restart. An arrangement satisfying these conditions is thus needed for efficient operation of the fuel cell system.
It is therefore an object of the present invention to provide a fuel cell system and method which can satisfy the conditions for efficient operation of the system during shutdown and/or restart.
It is also an object of the present invention to provide an integrated fuel cell system where the appropriate atmosphere is maintained in the anode and the cathode of the fuel cell of the system during shutdown, without physically isolating the two.
It is a further object of the present invention to provide an arrangement and method of the above type which is cost effective and simple.

Control assembly for controlling a fuel cell system during shutdown and restart


A subscriber A accommodated in an SSP is connected to a terminal to which a telephone number is assigned by a number conversion service. The communication state of the converted telephone number becomes in a busy state, and a corresponding SSP number is written in a management table arranged in an SCP. If a fault occurs in the SSP, all of the calls to which a subscriber accommodated in the SSP is connected, are released. Once the SSP is restored from the fault, it notifies the SCP of the SSP number identifying the SSP together with a message notifying that the SSP is restored from the fault. The SCP searches for a management table using the SSP number received from the SSP, and changes all of the communication states of converted telephone numbers corresponding to the corresponding SSP number to an idle state.

1. Field of the Invention
The present invention relates to a system and a method for managing a state of a communication using an intelligent network, and more particularly to a system and a method for managing a state of a communication using an intelligent network which provides a service to convert a predetermined number which is preregistered into a number identifying a destination.
2. Description of the Related Art
An intelligent network is a communications network which has been popularized by meeting the demand for enhancing its capabilities, and an information transfer network and a service control network are arranged hierarchically.
The information transfer network is composed of electronic switches called SSPs (Service Switching Points), SAPs (Service Access Points), etc. Each of the SSPs is intended to transfer a service request from a subscriber to a service control network, and to control a communications network according to an instruction given by the service control network.
The service control network normally includes servers called SCPs (Service Control Points) or NSPs (Network Service Control Points). Each of the SCPs includes an integrated database which normally stores subscriber information, network configuration information, service control software, etc., and integrates communications service capabilities such as a communication processing capability, service providing capability, path selection control capability, etc. The SCP provides a service (required communication control information) in response to a request made by the SSP.
FIG. 1 is a schematic diagram showing the configuration of a typical intelligent network. An SCP 101 and SSPs 102-1 through 102-n are connected via a switching node for a common channel signaling network, called an STP (Signaling Transfer Point) 103. Each of the SSPs 102-1 through 102-n transmits a service request to the SCP 101 via the STP 103, while the SCP 101 provides a service (required communication control information) to each of the SSPs 102-1 through 102-n via the STP 103, in response to the service request.
The intelligent network provides enhanced services such as putting a number system into a virtual form (logical form), enhanced routing control, flexible interconnection control, variable operation of a communications network, etc.
One of the services provided by the intelligent network is a service for converting a telephone number, represented by a toll-free number telephone service. Provided below is the explanation about an example of the number conversion service. Here, a service for changing a destination depending on the availability of a subscriber at a destination such as an FRS (Flexible Routing Service), is raised.
The SCP 101 includes a management table (database) 111 shown in FIG. 2A in order to provide the number conversion service. In this figure, "IN telephone number" is a virtual number contracted in advance. "converted telephone number" is a telephone number of an actual and normal subscriber. If a subscriber inputs a certain IN telephone number, that call is connected to any of terminals having converted telephone numbers corresponding to the input IN telephone number. "state" indicates whether a terminal (line) identified by a converted telephone number is either busy or idle.
If a subscriber "A" accommodated in the SSP 102-1 inputs an IN telephone number 0120-044-123, the SSP 102-1 transmits the IN number to the SCP 101 to request convertion of the number. When receiving this request, the SCP 101 searches for a management table 111, retrieves a converted telephone number in the idle state (for example, 044-123-4567) from converted telephone numbers corresponding to that IN number, and returns the retrieved number to the SSP 102-1. At this time, the SCP 101 changes the state of the retrieved number to the "busy" state in the management table 111.
Each of the SSPs 102-1 through 102-n includes a management table 112 shown in FIG. 2B. "line identification number" is a number for identifying a line accommodated in each of the SSPs 102-1 through 102-n. "receiver number" is a telephone number of a receiver of a terminal connected to a line identified by the line identification number. "state" indicates whether or not the line identified by the line identification number, or a terminal connected to that line, is busy.
When receiving the converted telephone number from the SCP 101, the SSP 102-1 establishes a call according to that number. The SSP 102-1 updates data regarding the subscriber A in the management table 112. Assuming that the line identification number of the line to which the subscriber A is connected is 002, the SSP 102-1 writes the converted telephone number which is received as the receiver number in correspondence with the line identification number, and updates its state to "busy".
If the subscriber A releases the call, the SSP 102-1 clears the receiver number in the management table 112, and updates its state to "idle". In the meantime, the SCP 101 updates the state of the converted telephone number 044-123-4567 to "idle" in the management table 111, when receiving the notification that the call was released from the SSP 102-1.
As described above, the number conversion service such as an FRS is provided by arranging the management table 111 which manages an idle/busy state of a subscriber at a destination in the SCP 101.
The link between the SCP 101 and each of the SSPs 102-1 through 102-n, however, is not established all the time. It is established depending on need (for example, at an access made by a service request). Therefore, if a fault occurs in the SCP 101 or any of the SSPs 102-1 through 102-n, the contents of the management table 111 arranged in the SCP 101 may sometimes be inconsistent with an actual communication state of any of the SSPs 102-1 through 102-n, at the time of restoration from the fault.
Such an inconsistent state causes the following problem. By way of example, assume that the state of the telephone number 044-123-4567 is "busy" in the management table 111 arranged in the SCP 101, although a call between the subscriber A and the terminal having the telephone number 044-123-4567 (hereinafter referred to as a subscriber B), is released. Physically, the subscriber B can receive a call in this case. However, if a certain subscriber inputs the IN telephone number 0120-044-123, the SCP 101 regards the telephone number 044-123-4567 as being busy. Accordingly, the IN number 0120-044-123 is not converted into the telephone number 044-123-4567 in the number conversion service. That is, that line cannot be used even though the line of the subscriber B is actually available. As a result, the communication resource is not used properly.
The above described problem is due to an inconsistency between the contents of the management table 111 arranged in the SCP 101 and the actual communication state.
As a technique for monitoring the normality of the service between the SCP 101 and the SSPs 102-1 through 102-n, the invention "TOKKAIHEI 6-46129, for example, is known. This invention discloses a monitoring system for monitoring an entire network including an SCP and SSPs, and restarting the SCP or SSPs if a fault is detected. According to such a system for restarting the SCP or the SSPs, however, the service is forced to be halted. Specifically, if the SCP is restarted, it causes an undesirable phenomenon. That is, all of services are halted. Furthermore, a simple restart of the SCP or the SSPs cannot make the communication states that the SCP manages consistent with the actual communication states of the SSPs.

Communication state management system and method in an intelligent network