Reverse Antenna Effect: A Hidden Reliability Risk in BEOL Interconnects

Plasma-induced damage (PID) is a major cause of yield loss in standard semiconductor fabrication, typically driven by plasma charging during dielectric or metal etching process. This kind of damage usually hits devices with gate dielectrics, where accumulated charge leads to dielectric breakdown. To prevent it, design rules based on metal-to-gate area ratios are applied. This study examines a less explored failure mode known as reverse antenna charging. Here, the damage doesn’t occur at the gate dielectric but within the back-end-of-line (BEOL) interconnects, away from the front-end-of-line (FEOL) devices. Phenomenon was first observed in product and then test structures were built for thick oxide gate dielectric devices through a common BEOL interconnect path strategy. Gates were routed through CA, M1, V1, M2, V2, and M3 layers, with failures observed at the M1-V1 levels for structures connected to thick gate devices when discharge paths were intentionally designed to be weak. Under these conditions, reverse charging effects were successfully isolated and reproduced, resulting in hard open failures. The results confirm that yield loss can still occur even when thick gate devices are designed according to existing antenna rule strategies. This points to a failure mechanism that current rules did not address. As a result, a need is identified for existing design strategies to be revised to account for reverse antenna charging and its impact on BEOL interconnect reliability.