Polarity Dependence and Metal Density Impact on Multi-Layer Inter-Level TDDB for High Voltage Application

For high voltage application at a fixed inter-metal distance, dielectric reliability has been investigated on multi-layer inter-level interconnects, focusing on conduction mechanism and geometry effect. From Vramp (voltage-ramp-to-breakdown) tests, Vbd is found to be 4-5% lower with positive bias applied to the bottom metal, which is believed to be due to the polarity-dependent conduction mechanism. IV characteristics of two different bias configurations at various temperatures suggest that Poole-Frenkel and Fowler-Nordheim, respectively, dominates for a high bias to the bottom and top electrodes. In addition, metal density affects the lifetime of inter-level TDDB (time dependent dielectric breakdown) with Poisson area scaling. Based on our studies, a guideline for additional reliability margin can be proposed by bias polarity restriction and layout design optimization.