Effect of plasma treatment on adhesion of low thermal expansion polyimide films

Abstract To fabricate a multilayer wiring using a low thermal expansion polyimide film, the adhesion of polyimide film on a thermally cured polyimide film must be secured. When the surface was plasma‐treated by O 2 ‐CF 4 = 1:1 gas, the adhesion was 30 times stronger (peel strength: at least 500 g/cm) than in the untreated case (peel strength: 15 g/cm). The film on the plasma‐treated surface maintained strong adhesion for long periods of time in a high‐temperature and high‐humidity environment. The cause of improved adhesion was investigated by evaluating the plasma‐treated polyimide surface by XPS and it was found that functional group, which seems to be COF, was formed.