This study examines the metal/polymer interfacial adhesion strength for Cu, Ti and three polymers, BCB, SU-8 and AZ 4620. Detailed discussion and explanation focused on adhesion mechanism between metal and BCB, AZ 4620 dielectric are provided. The adhesion strengths of metal on polymer layer are measured by four point bending (FPB) test, which showed that copper and titanium have different characteristics in metal-polymer adhesion. Additionally, to figure out the interfacial adhesion mechanisms, X-ray photoelectron spectroscopy (XPS) technique is used to investigate the chemical bonding compositions between interfaces. The results indicate that the adhesion strength is enhanced by the intense reaction between metal and oxygen on the polymer main chain at the metal-polymer interfaces. On the other hand, interfacial adhesion strength is weaken owing to the destruction of polymer structure, thus the bonding between metal and polymer-main-chain debonded oxygen are of no effect on adhesion.