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C 1 -C$_{12 }$ alkanediyl group which may contain a carbonyl moiety, ester bond or ether bond. Z 3 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, -O-Z 31 -, C(=O)---0-Z 31 -, or ----C(=O)-NH› Z31-, Z 31 is a C 1 -C 6 alkanediyl group, C 2 -C 6 alkenediyl group, phenylene group, fluorinated phenylene group, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxyl moiety. R 21 to R 28 are each independently a C 1 -C$_{20 }$ monovalent hydrocarbon group which may contain a het› eroatom, any two ofR 23 , R 24 and R 25 or any two ofR 26 , R 27 and R 28 may bond together to form a ring with the sulfur atom to which they are attached. "A" is hydrogen or trifluoromethyl. M- is a non-nucleophilic counter ion. 

[0025] In another aspect, the invention provides a process for forming a pattern comprising the steps of applying the resist composition defined herein to form a resist film on a substrate, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer. 

[0026] Typically, the high-energy radiation is ArF excimer laser radiation of wavelength 193 nm, KrF excimer laser radiation of wavelength 248 nm, EB, or EUV of wavelength 3 to 15 nm. 

[0027] The amine compound having an iodized aromatic ring is fully absorptive to EUV due to iodine, has a sensi› tizing effect, and is quite effective for suppressing acid diffusion by virtue of the large atomic weight of iodine. Since the amine compound also has an acid-decomposable tertiary ester structure, it is decomposed with acid in the exposed region and converted to an amine compound having a lower molecular weight. As a result, the acid in the exposed region becomes more active and the contrast is improved. There are obtained advantages including low diffusion, high contrast, high sensitivity, low LWR, and improved CDU. Thus a resist composition having a high sensitivity, low LWR and improved CDU is designed. 

[0028] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. The notation (Cn-Cm) means a group containing from n to m carbon atoms per group. As used herein, the term "iodized" compound means an iodine› substituted compound. In chemical formulae, Me stands for methyl, and Ac for acetyl. 

[0029] The abbreviations and acronyms have the follow› ing meaning. 

[0030] EB: electron beam 

[0031] EUV: extreme ultraviolet 

[0032] Mw: weight average molecular weight 

[0033] Mn: number average molecular weight 

[0034] Mw/Mn: molecular weight dispersity 

[0035] GPC: gel permeation chromatography 

[0036] PEB: post-exposure bake 

[0037] PAG: photoacid generator 

[0038] LWR: line width roughness 

[0039] CDU: critical dimension uniformity 

## Advantageous Effects of Invention 

## DESCRIPTION OF EMBODIMENTS 

## Resist Composition 

[0040] The resist composition of the invention is defined as comprising a base polymer and a quencher containing an amine compound having an iodized aromatic ring and a tertiary ester structure. 

## Amine Compound 

[0041] The quencher contains an amine compound having an iodized aromatic ring and a tertiary ester structure. Specifically the amine compound has the formula (A-1) or (A-2). 

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[0042] In formulae (A-1) and (A-2), Xis a single bond or a C 1 -C$_{20 }$divalent linking group. The divalent linking group may be straight, branched or cyclic. Examples include straight or branched alkanediyl groups such as methylene, ethylene, propane-1,2-diyl, propane-1,3-diyl, butane-1,2- diyl, butane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-I, 7-diyl, octane-1,8-diyl, nonane- 1,9-diyl, decane-1,10-diyl, undecane-1,1-diyl, and dode› cane-1,12-diyl; C 3 -C 20 divalent saturated cyclic hydrocar› bon groups such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; C 2 -C 20 divalent unsaturated aliphatic hydrocarbon groups such as vinylene and propene-1,3-diyl; CcC$_{20 }$ divalent aromatic hydrocarbon groups such as phenylene and naphthylene; and mixtures thereof. The divalent linking group may contain an ether bond, carbonyl moiety, ester bond, amide bond, sultone ring, lactam ring, carbonate bond, halogen, hydroxyl moiety or carboxyl moiety. 1 

[0043] In formulae (A-1) and (A-2), R is hydrogen, hydroxyl, an optionally halo-substituted C 1 -C 6 alkyl group, optionally halo-substituted C 1 -C 6 alkoxy group, optionally halo-substituted C 2 -C 6 acyloxy group, optionally halo-sub› stituted C 1 -C 4 alkylsulfonyloxy group, fluorine, chlorine, bromine, amino, nitro, cyano, -NR 1 A-C(=O)-R 1$_{B,}$ or -NR 1 A----C(=O---0-R 1$_{B,}$ $_{wherein R}$1 A is hydrogen or a C 1 -C 6 alkyl group, and RIB is a C 1 -C 6 alkyl group or C 2 -C 5 alkenyl group. 

[0044] The C 1 -C 6 alkyl group may be straight, branched or cyclic, and examples thereof include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert› butyl, cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, and cyclo› hexyl. Examples of the alkyl moiety in the C 1 -C 6 alkoxy, C 2 -C 6 acyloxy or C 1 -C 4 alkylsulfonyloxy group are as exemplified above for the alkyl group of 1 to 6, 1 to 5, or 1 to 4 carbon atoms. 

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