Excimer laser pretreatment and metallization of polymers

Abstract

Metal/polymer adhesion is a crucial factor of many applications in microelectronic or microsystem technologies. It depends on chemical and structural properties of the interface, often involving just a few atomic layers. Adhesion can be influenced by various pretreatments prior to metal deposition, e.g. thermal treatment, chemical etching or exposure to reactive plasmas. Irradiation with pulsed UV-laser radiation and or UV-excimer lamps can also affect adhesion and offers several technical advantages, among them area selective pretreatment and subsequent metallization. The pretreatment of polymer surfaces by UV-radiation is investigated as an alternative technique to common wet chemical, plasma or other pretreatment methods. Chemical and morphological changes in the polymer surface are investigated with poly(butylene terephthalate) (PBT) as a model substance, containing UV-absorbing (aromatic) chromophoric groups. Chemical changes in the surface are investigated via X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Analysis of the morphological changes in the polymer surface is done via optical microscopy and scanning electron microscopy (SEM). The metallization of polymers pretreated by excimer laser radiation is performed via electroless plating of nickel followed by electrolytically deposited copper. The influence of excimer laser irradiation of the polymer on the adhesion of the metal overlayers is measured by tape and peel tests.