Adhesion of sputter-deposited Cu/Ti film on plasma-treated polymer substrate

The effect of Ar plasma pretreatment on the adhesion of the sputter-deposited Cu/Ti film, which was used as a seed layer for subsequent electrodeposition of thick Cu film, on an Ajinomoto build-up film (ABF) was evaluated as a function of the plasma power. The Ar plasma pretreatment of the ABF (above 1.2kW) surface resulted in three-fold increase of the peel-off strength (0.70kN/m) compared to the untreated sample (0.23kN/m). The Ar plasma treatment produced a nanoscale worm-like surface roughness on the ABF surface which was responsible for the improved adhesion of the Cu/Ti film. Examination of the fractured surfaces revealed that when the substrate was plasma-treated above 1.2kW, the fracture occurred in the substrate rather than by delamination of the Cu/Ti film. In fact, the fracture of the ABF substrate, which consists of the SiO2 filler embedded in a polymer resin matrix, proceeded mainly by decohesion of the SiO2 microspheres from the polymer matrix. Hence, to further improve the adhesion of the Cu/Ti film, it is advisable to consider strengthening the interface between the SiO2 filler and the resin matrix through surface modification of the SiO2 microspheres. •ABF substrate was Ar-plasma-treated to improve the adhesion of Cu/Ti film.•Plasma treatment above 1.2kW significantly increased of the peel-off strength.•Nanoscale roughness was found on the Ar plasma-treated ABF surface.•In the untreated sample, the fracture proceeded through the Ti/ABF interface.•In the plasma-treated sample, the fracture occurred through the bulk of the ABF.