Poly(oxybenzoate-co-oxynaphthoate) (POCO) film surfaces were modified with remote oxygen plasma, and the effects of the modification on the adhesion between the copper layer and POCO were investigated. The remote-oxygen-plasma treatment led to a noticeable decrease in the contact angle, which was mainly due to the C-O functional groups on the surface. The modification of the POCO surface by remote oxygen plasma was effective in improving the adhesion with copper metal. The peel strength for the copper metal/POCO system was enhanced from 10 to 127.5 mN/5 mm by the surface modification. The failure mode of the copper metal/POCO system was an interface layer between the oxidized micro-POCO fibril surface and the copper metal layer. (C) 2003 Wiley Periodicals, Inc.