ether acetate; and lactones such as y-butyrolactone, which may be used alone or in admixture. 

[0145] The organic solvent is preferably added in an amount of 100 to 10,000 parts, and more preferably 200 to 8,000 parts by weight per 100 parts by weight of the base polymer. 

[0146] Other Components 

[0147] With the foregoing components, other components such as a surfactant, dissolution inhibitor, and crosslinker may be blended in any desired combination to formulate a chemically amplified positive or negative resist composi› tion. This positive or negative resist composition has a very high sensitivity in that the dissolution rate in developer of the base polymer in exposed areas is accelerated by catalytic reaction. In addition, the resist film has a high dissolution contrast, resolution, exposure latitude, and process adapt› ability, and provides a good pattern profile after exposure, and minimal proximity bias because of restrained acid diffusion. By virtue of these advantages, the composition is fully useful in commercial application and suited as a pattern-forming material for the fabrication of VLSis. 

[0148] Exemplary surfactants are described in JP-A 2008- 111103, paragraphs [0165]-[0166]. Inclusion of a surfactant may improve or control the coating characteristics of the resist composition. While the surfactant may be used alone or in admixture, it is preferably added in an amount of 0.0001 to 10 parts by weight per 100 parts by weight of the base polymer. 

[0149] In the case of positive resist compositions, inclu› sion of a dissolution inhibitor may lead to an increased difference in dissolution rate between exposed and unex› posed areas and a further improvement in resolution. The dissolution inhibitor which can be used herein is a com› pound having at least two phenolic hydroxyl groups on the molecule, in which an average of from Oto 100 mo! % of all the hydrogen atoms on the phenolic hydroxyl groups are replaced by acid labile groups or a compound having at least one carboxyl group on the molecule, in which an average of 50 to 100 mo!% of all the hydrogen atoms on the carboxyl groups are replaced by acid labile groups, both the com› pounds having a molecular weight of 100 to 1,000, and preferably 150 to 800. Typical are bisphenol A, trisphenol, phenolphthalein, cresol novolac, naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic acid derivatives in which the hydrogen atom on the hydroxyl or carboxyl group is replaced by an acid labile group, as described in U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs [0155]-[0178]). 

[0150] In the positive resist composition, the dissolution inhibitor is preferably added in an amount of 0 to 50 parts, more preferably 5 to 40 parts by weight per 100 parts by weight of the base polymer. The dissolution inhibitor may be used alone or in admixture. 

[0151] In the case of negative resist compositions, a nega› tive pattern may be formed by adding a crosslinker to reduce the dissolution rate of a resist film in exposed area. Suitable crosslinkers which can be used herein include epoxy com› pounds, melamine compounds, guanamine compounds, gly› coluril compounds and urea compounds having substituted thereon at least one group selected from among methylol, alkoxymethyl and acyloxymiethyl groups, isocyanate com› pounds, azide compounds, and compounds having a double bond such as an alkenyl ether group. These compounds may be used as an additive or introduced into a polymer side 

chain as a pendant. Hydroxy-containing compounds may also be used as the crosslinker. The crosslinker may be used alone or in admixture. 

[0152] Of the foregoing crosslinkers, examples of the epoxy compound include tris(2,3-epoxypropyl) isocyanu› rate, trimethylolmethane triglycidyl ether, trimethylolpro› pane triglycidyl ether, and triethylolethane triglycidyl ether. Examples of the melamine compound include hexamethylol melamine, hexamethoxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups methoxymethylated and mixtures thereof, hexamethoxy› ethyl melamine, hexaacyloxymethyl melamine, hexameth› ylol melamine compounds having 1 to 6 methylol groups acyloxymethylated and mixtures thereof. Examples of the guanamine compound include tetramethylol guanamine, tetramethoxymethyl guanamine, tetramethylol guammnine compounds having 1 to 4 methylol groups methoxymethyl› ated and mixtures thereof, tetramethoxyethyl guanamine, tetraacyloxyguamnnine, tetramethylol guanamine com› pounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the glycoluril compound include tetramethylol glycoluril, tetramethoxyglycoluril, tetramethoxymethyl glycohluril, tetramethylol glycoluril compounds having 1 to 4 methylol groups methoxymethyl› ated and mixtures thereof tetramethylol glycoluril com› pounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the urea compound include tetramethylol urea, tetramethoxymethyl urea, tetramethylol urea compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, and tetramethoxyethyl urea. 

[0153] Suitable isocyanate compounds inchlude tolylene diisocyanate, diphenylmethane diisocyanate, hexamethyl› ene diisocyanate and cyclohexane diisocyanate. Suitable azide compounds include 1,1’-biphenyl-4,4’-bisazide, 4,4’› methylidenebisazide, and 4,4’-oxybisazide. Examples of the alkenyl ether group-containing compound include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2- propanediol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, trimethylol propane trivinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tet› ravinyl ether, sorbitol pentavinyl ether, and trimethylol propane trivinyl ether. 

[0154] In the negative resist composition, the crosslinker is preferably added in an amount of 0.1 to 50 parts, more preferably 1 to 40 parts by weight per 100 parts by weight of the base polymer. 

[0155] In the resist composition of the invention, a quencher other than the inventive cyclic ammonium salt may be blended. The other quencher is typically selected from conventional basic compounds. Conventional basic compounds include primary, secondary, and tertiary ali› phatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing to compounds with carboxyl group, nitrogen-containing compotmds with sulfonyl group, nitrogen-containing compounds with hydroxyl group, nitro› gen-containing compounds with hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide deriva› tives, imide derivatives, and carbamate derivatives. Also included are primary, secondary, and tertiary amine com› pounds, specifically amine compounds having a hydroxyl group, ether bond, ester bond, lactone ring, cyano group, or 

