Improvement of adhesion of copper on polyimide by reactive ion-beam etching

In this paper we describe the effect of oxygen-reactive ion-beam etching of a polyimide film to enhance its adhesion to an overlying, subsequently deposited copper film. The adhesion strength of the copper to the polyimide could be increased by as much as a factor of 25 as a result of the etching. Near the etching condition which resulted in optimum strength, the failure mode at the polyimide/copper interface changed from adhesive failure to tensile failure. The latter occurred at the “roots” of a “grass-like” surface structure of the ion-etched polyimide film.