Significant improvement of adhesion between gold thin films and a polymer

Abstract

A novel technique was demonstrated for realizing extremely strong adhesion between gold thin films and a polysiloxane based polymer. The surface of the polymer was modified by using a plasma treatment. The variation of the wettability and topography of the polymer surface with the plasma conditions were investigated through water contact angle measurement and scanning electron microscope observation, respectively. It was found that the polymer surface was roughened greatly, and its water contact angle was reduced from 81 to 0° by using 1 min of O 2/CF 4 plasma treatment. The pull-off strength of the Au film from the polymer was enhanced from 1.2 to 8.5 N/mm 2 after the plasma treatment. Further improvement of the adhesion was achieved by sputter-coating two adhesion layers, Al 2O 3/Al, on the polymer before coating the Au film and annealing the films at 150 °C for 2 h. The pull-off strength of the Au film from such a polymer/Al 2O 3/Al/Au system was over 35 N/mm 2. The extremely strong bonding between the Au and the rest layers of the system was explained mainly by the formation of Au–Al alloys at the interface between the Al and Au layers based on an analysis using chemical etch and energy dispersive X-ray spectroscopy.