Evaluation of Cu(V) self-forming barrier for Cu metallization

Abstract

The properties of Cu(V) alloy films were investigated to evaluate its potential use as self-forming diffusion barrier in copper metallization. Cu(V) alloy films were deposited on SiO2/Si substrates by magnetron sputtering. Cu(V)/SiO2/Si systems were subsequently annealed at various temperatures and analyzed by four-point probe measurement (FPP), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). After annealed at 500 °C, the resistivity of the Cu(V) films reduced to 3.1 μΩ cm, there is no obvious increase in resistivity. XRD suggest that Cu alloy film has preferential (111) crystal orientation and no extra peak corresponding to Cu and Si even after annealed at 500 °C. According to TEM results, a self-formed thin layer with the thickness of about 8 nm is observed at the interface between Cu alloy and the SiO2/Si substrate in the sample annealed at400 °C. As XPS results, after annealed at 400 °C and 500 °C, V atoms are observed at the surface of the Cu(V) films and the interface of the Cu(V) and SiO2/Si. The formation of the self-formed thin layer is probably due to the separation of V at the interface. The sharp declines of the Cu and Si concentrations at the interface indicate a lack of inter-diffusion between Cu and SiO2/Si. Adding small amounts of V to Cu film can improve the barrier performance and thermal stability compared with pure Cu contact systems.