content_image/886572.jpg content_image/886573.jpg content_image/886574.jpg content_image/886575.jpg content_image/886576.jpg
mo! %, more preferably at least 5 mo! %. The upper limit is the same as above. When constituent units having formula ( 6a) or ( 6b) are incorporated, the molar fraction of units (Al) and/or (A2), especially (A2) may be accordingly reduced. 

## (B) Ammonium Salt 

[0077] Also essentially, the resist composition comprises an ammonium salt having the general formula (3). 

<img src='content_image/886572.jpg'>

Herein R 1 to R 4 are each independently a straight C$_{1}$-C$_{20}$, branched or cyclic C$_{3}$ -C$_{20 }$ monovalent hydrocarbon group which may be substituted with or separated by a heteroatom, any two or more of R 1 to R 4 may bond together to form a ring with the nitrogen atom to which they are attached. x› is a structure of the general formula (3a), (3b) or (3c): 

<img src='content_image/886573.jpg'>

<img src='content_image/886574.jpg'>

<img src='content_image/886575.jpg'>

wherein wa, Rfi’ 1 , Rfi’ 2 , wc1, wc 2 and R’c3 are each inde› pendently fluorine or a straight C$_{1 }$-C$_{40}$, branched or cyclic C$_{3}$ -C$_{40 }$monovalent hydrocarbon group which may be sub› stituted with or separated by a heteroatom, or a pair of Rfi’ 1 and Rfi’ 2 , or R’c1 and R’c $^{2 }$may bond together to form a ring with the carbon atom to which they are attached and any intervening atoms. 

[0078] In the cation moiety in formula (3), examples of the hydrocarbon group represented by R$^{1 }$to R 4 include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert› pentyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclo› pentyl, cyclohexyl, 2-ethylhexyl, cyclopentylmethyl, cyclo› pentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexy lethy I, cyclohexy lbuty I, norborny I, oxanorborny I, tricyclo[5.2.l .0 2 • $^{6}$]decanyl, adamantyl, phenyl, naphthyl and anthracenyl. Also included are the foregoing groups in which at least one hydrogen atom is replaced by a heteroa› tom such as oxygen, sulfur, nitrogen or halogen, or in which a heteroatom such as oxygen, sulfur or nitrogen intervenes between carbon atoms, so that a hydroxyl radical, cyano radical, carbonyl radical, ether bond, ester bond, sulfonic 

acid ester bond, carbonate bond, lactone ring, sultone ring, carboxylic acid anhydride, or haloalkyl radical may form or intervene. Those structures shown below are preferable because of availability, but the cation is not limited thereto. 

<img src='content_image/886576.jpg'>

(3) 

(3a) 

(3b) 

(3c) 

