The present invention provides a carboxyl sulfonate compound and preparation method thereof. The present carboxyl sulfonate compound has structure of formula (A):

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wherein M.sub.1 is hydrogen or an alkali metal; M.sub.2 is hydrogen, alkyl or an alkali metal; Y is hydrogen, alkyl; carboxyl, carboxyl salt; alkylcarboxyl, or alkylcarboxyl salt; n is an integer from 1 to 10; and m is an integer from 1 to 10. The carboxylic group and the sulfonic acid group in the structure of the present carboxyl sulfonate compound show excellent chelating ability to metal ions; therefore, the present carboxyl sulfonate compound is particularly for use in electroplating additive.

Disclosed is a sulfanyl sulfonic acid compound represented by the following formula (1) or a metal salt thereof. In the formula, m represents an integer of 2 to 7, n represents an integer of 3 to 10, and R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group. ##STR00001##

Disclosed is a sulfanyl sulfonic acid compound represented by the following formula (1) or a metal salt thereof. In the formula, m represents an integer of 2 to 7, n represents an integer of 3 to 10, and R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group. ##STR00001##

A radiation-sensitive composition includes: an onium salt compound represented by formula (1); a polymer including a structural unit (I) which includes an acid-dissociable group; and a solvent. W is a cyclic structure having 3 to 40 ring members formed together with the two carbon atoms; a formula between the two carbon atoms below represents a single bond or a double bond, , A is one of groups represented by formulae (A-1) to (A-7); R.sup.1 is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxy group, a hydroxy group, an amino group, a halogen atom, or a thiol group, when there are a plurality of R.sup.1s, the plurality of R.sup.1s are same as or different from each other; m.sub.1 is an integer of 0 to 4; and Z.sup.+ is a monovalent radiation-sensitive onium cation.

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A radiation-sensitive composition includes: an onium salt compound represented by formula (1); a polymer including a structural unit (I) which includes an acid-dissociable group; and a solvent. W is a cyclic structure having 3 to 40 ring members formed together with the two carbon atoms; a formula between the two carbon atoms below represents a single bond or a double bond, , A is one of groups represented by formulae (A-1) to (A-7); R.sup.1 is a monovalent organic group having 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxy group, a hydroxy group, an amino group, a halogen atom, or a thiol group, when there are a plurality of R.sup.1s, the plurality of R.sup.1s are same as or different from each other; m.sub.1 is an integer of 0 to 4; and Z.sup.+ is a monovalent radiation-sensitive onium cation.

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