Molecular resist composition and patterning process

A molecular resist composition comprising a sulfonium salt having the formula (1) and an organic solvent,

• wherein Ar1, Ar2 and Ar3 are each independently a C6-C20 aryl group in which some or all of the hydrogen atoms on its aromatic ring may be substituted by halogen or a C1-C20 hydrocarbyl group which may contain a heteroatom, at least one of Ar1, Ar2 and Ar3 is substituted with a group having the formula (1a), (1b) or (1c), any two of Ar1, Ar2 and Ar3 may bond together to form a ring with the sulfur atom to which they are attached,
• wherein Ra1, Ra2 and Ra3 are each independently hydrogen or a C1-C10 hydrocarbyl group;
• Rb1, Rb2 and Rb3 are each independently a C1-C10 hydrocarbyl group, Rb1 and R2 may bond together to form a ring with the carbon atom to which they are attached;
• Rc1 and Rc2 are each independently hydrogen or a C1-C10 hydrocarbyl group, Rc3, Rc4 and Rc5 are each independently a C1-C10 hydrocarbyl group, Rc3 and Rc4 may bond together to form a ring with the carbon atom to which they are attached;
• the broken line designates a valence bond, and
• X− is an anion, exclusive of BF4−, PF6−, SbF6− and anions having the following formulae (ex1) to (ex4):
• wherein Rex1 is halogen or a C1-C40 hydrocarbyl group which may contain a heteroatom;
• Rex2, Rex3, Rex4, Rex5 and Rex6 are each independently fluorine or a C1-C40 hydrocarbyl group which may contain a heteroatom, Rex2 and Rex3 may bond together to form a ring with the carbon atoms to which they are attached and intervening atoms, Rex4 and Rex5 may bond together to form a ring with the carbon atoms to which they are attached and intervening atoms;
• Rex7 is halogen, hydroxy or a C1-C40 hydrocarbyl group which may contain a heteroatom;
• Rex8 and Rex9 are each independently fluorine or trifluoromethyl.