Reliability of the Cu/low-k structure is a serious concern since the metal/dielectric interface is generally weak. The adhesion of the Ta/polyarylene ether interfaces with and without electron beam (EB) treatment was investigated by four-point bending test, x-ray photoelectron spectroscopy, and density functional theory. Higher adhesion energy (Gc) was achieved with low-dose EB treatment, attributed to the strong Ta-arene interaction. However, high-dose EB breaks the aromatic rings partially, resulting in fewer available sites for Ta-arene bonding, leading to lower adhesion. It is suggested that the amount of carbon atoms involved in bonding with the metal is the key to improve the Ta/polymer adhesion.