| abstract |
The present invention relates to a photo acid generator which has high transparency to exposure light and also has excellent heat stability in a photoresist composition for lithography using far ultraviolet light, especially light of ArF excimer laser. The photo acid generator contains a sulfonium salt compound represented by the following general formula (1): n n n wherein R 1 represents an alkylene group, or an alkylene group having an oxo group, R 2 represents a straight-chain, branched-chain, monocyclic, polycyclic or bridged cyclic alkyl group having an oxo group, or a straight-chain, branched-chain, monocyclic, polycyclic or bridged cyclic alkyl group, provided that either of R 1 and R 2 has an oxo group, and Y − represents a counter ion. |