Ru Stress Assessment by Membrane Wrinkling for Interconnect Applications

The stress evolution of PVD Ruthenium (Ru) thin films is studied at relevant temperatures for interconnect processing. Wafer bow measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), microelectromechanical systems (MEMS) and the Foppl-von Karman theory were used to determine the stress behavior of 5 to 50 nm thick films. We show that the local relaxation of PVD Ru film results in two regimes: bending and wrinkling, depending on stress and film thickness.