Onium salt, chemically amplified resist composition, and pattern forming process

An onium salt having the following formula (1):

• wherein R1 to R12 are each independently a hydrogen atom, a halogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom,
• one of R13 and R14 is a group having a partial structure of the following formula (1a), the other one is a hydrogen atom, a halogen atom, or a C1-C20 hydrocarbyl group which may contain a heteroatom,
• at least two of R1 to R14 may bond together to form a ring with the carbon atom to which they are attached or with the carbon atom to which they are attached and the carbon atom therebetween, and
• Z+ is an onium cation,
• wherein LA and LB are each independently a single bond, an ether bond, an ester bond, a sulfonic acid ester bond, a carbonate bond, or a carbamate bond,
• XL is a single bond or a C1-C40 hydrocarbylene group which may contain a heteroatom,
• Q1 to Q3 are each independently a hydrogen atom, a fluorine atom, or a C1-C6 fluorinated saturated hydrocarbyl group, provided that, when both of Q1 and Q2 are a hydrogen atom, Q3 is a fluorine atom or a C1-C6 fluorinated saturated hydrocarbyl group, and the total number of fluorine atoms in Q1 to Q3 is 2 or more.