Electrical reliability and interfacial adhesion of Cu(Mg) thin films for interconnect process adaptability

Abstract

The process adaptability of Cu(0.7–1.2 at.% Mg) alloy films for microelectronics interconnects was investigated by comparing their electrical properties, interfacial adhesion strength, time dependent dielectric breakdown (TDDB) reliabilities, and interfacial microstructure with those of pure Cu. The resistivity of the Cu(Mg) films decreased to ∼ 2.0 μΩ cm after annealing them in a vacuum at 350 °C for 10 min. The interfacial debonding energy measured by the four-point bending method was approximately 20.1 J/m 2 for Cu(Mg)/SiO 2 which is a factor of 2.3 larger than that of Cu/SiO 2 interfaces. The median time to failure of Cu(Mg)/SiO 2 in the TDDB test was much larger than that of pure Cu/SiO 2. The diffusion of Cu into the dielectric was found to be inhibited by the continuous very thin Mg–O layer formed at the Cu(Mg)/SiO 2 interface, which improves the interfacial adhesion, and ultimately leads to better electrical reliabilities.