A percolative approach to reliability of thin film interconnects and ultra-thin dielectrics

We present a new percolative approach which simulates degradation towards failure of metallic or insulating thin films. The thin film is modelled as a two-dimensional random resistor network in thermal contact with a substrate. Its degradation is characterized by a breaking probability of the single resistor related to the substrate temperature and to Joule heating effects. The dependence of the single resistor on the local temperature is taken into account as well as its thermal interaction with nearest neighbours. The failure of metallic strips and ultra-thin dielectrics are then described as a conductor-insulator (CI) and an insulator-conductor (IC) transition, respectively. A recovery of the damage competing with the degradation is introduced which accounts for healing processes and can eventually lead to a steady-state condition. This approach can model the resistance degradation of metal interconnects by electromigration phenomena and the pre-breakdown of ultrathin dielectric where stress induced leakage currents (SILC) are used to monitor the degradation. The main features of experiments are reproduced together with their statistical properties. Our approach thus provides a unified framework for studying degradation and failure in both metallic and dielectric thin films.