An experimental methodology for the in-situ observation of the time-dependent dielectric breakdown mechanism in Copper/low-k on-chip interconnect structures

This study captures the time-dependent dielectric breakdown kinetics in nanoscale Cu/low-k interconnect structures, applying in-situ transmission electron microscopy (TEM) imaging and post-mortem electron spectroscopic imaging (ESI). A “tip-to-tip” test structure and an experimental methodology were established to observe the localized damage mechanisms under a constant voltage stress as a function of time. In an interconnect structure with partly breached barriers, in-situ TEM imaging shows Cu nanoparticle formation, agglomeration and movement in porous organosilicate glasses. In a flawless interconnect structure, in-situ TEM imaging and ESI mapping show close to no evidence of Cu diffusion in the TDDB process. From the ESI mapping, only a narrow Cu trace is found at the SiCN/OSG interface. In both cases, when barriers are breached or still intact, the initial damage is observed at the top interface of M1 between SiCN and OSG.