Sulfonium compound, resist composition, and patterning process

A sulfonium compound having the formula (1):

• Z—X-L1-SO3− (1)
• wherein L1 is a straight, branched or cyclic C1-C20 divalent hydrocarbon group which may contain a heteroatom-containing moiety, X is an ether bond, and Z is a group of sulfonium cation structure having the formula (1A), (1B) or (1C):
• wherein the broken line denotes a valence bond to X,
• A is a single bond, methylene, carbonyl, sulfinyl, sulfonyl, amino, ether bond, thioether bond, ester bond, carbonate bond, carbamate bond or sulfonic acid ester bond,
• R1a to R1c are each independently a straight, branched or cyclic C1-C20 monovalent hydrocarbon group which may contain a heteroatom-containing moiety, at least one of R1a to R1c being a group of the formula (1-1) shown below, with the proviso that where at least two R1a are included, two of them may bond together to form a ring with carbon atoms on the benzene ring to which they are attached, where at least two R1b are included, two of them may bond together to form a ring with carbon atoms on the benzene ring to which they are attached, and where at least two R1c are included, two of them may bond together to form a ring with carbon atoms on the benzene ring to which they are attached,
• m1, m2 and m3 are integers in the range:
• 0≤m1≤5, 0≤m2≤5, 0≤m3≤4, and m1+m2+m3≥1,
• n1, n2 and n3 are integers in the range:
• 0≤n1≤4, 0≤n2≤4, 0≤n3≤4, and n1+n2+n3≥1,
• k1, k2 and k3 are integers in the range:
• 0≤k1≤5, 0≤k2≤4, 0≤k3≤3, and k1+k2+k3≥1,
• wherein L2 is a straight, branched or cyclic C1-C20 divalent hydrocarbon group which may contain a heteroatom-containing moiety, Rf1 and Rf2 are each independently hydrogen, a straight, branched or cyclic C1-C20 alkyl, fluorine, or straight, branched or cyclic C1-C20 fluoroalkyl having at least one fluorine atom, at least one of Rf1 and Rf2 being fluorine or fluoroalkyl, the broken line denotes a valence bond.