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

Abstract

aryl groups having an acid labile group of ether form are present on an aromatic ring having -SO3- bonded thereto, and at least one aryl group having an ether type acid labile group is bonded to a carbon atom adjoining the carbon atom to which -SO3- is bonded generates an arenesulfonic acid with adequate acidity and controlled diffusion. A chemically amplified positive resist composition comprising the onium salt has a high resolution and forms a pattern of rectangular profile with reduced LER and few development defects.

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