The Role of Atomic Displacements in Ion-Induced Dielectric Breakdown

Irradiation of electronic devices with heavy ions causes a range of device degradation and failure modes, many of which are characterized and/or triggered by enhanced leakage current through dielectric layers. These damage modes include single-event dielectric rupture (SEDR), long-term reliability degradation (LTRD), and radiation-induced soft breakdown (RISB), and they play a major role in limiting device lifetime and reliability in space applications. The LET-induced transient carrier plasma that is generated along the incident ion path has traditionally been understood as the physical effect ultimately leading to damage in dielectric layers. However, in a recent study we showed that nontrivial densities of atomic displacements are directly generated by incident heavy ions. Here, we report multiscale calculations of the effects of ion-induced atomic displacements on the current-voltage (I-V) characteristics of SiO₂ layers. We use both parameter-free quantum mechanical calculations and 3D percolation theory calculations based on Mott defect-to-defect tunneling. We show that ion-induced atomic displacements produce both transient and static low-resistivity paths through SiO₂ layers. The calculated I-V characteristics of damaged SiO₂ layers agree quantitatively with experimental data and are shown to depend on both the spatial distribution of displacement-induced defects and the distribution of defect energy levels in the SiO₂ energy gap.