Successive breakdown mode of time-dependent dielectric breakdown for Cu interconnects and lifetime enhancement under dynamic bias stress

Successive breakdown (BD) has recently been observed during the back end of line (BEOL) process as the technology nodes progress. For gate dielectrics, successive BD is caused by randomly generated bond breakages of the dielectrics, whereas successive BD in inter-metal dielectrics has not been sufficiently investigated. In this work, it is confirmed that the successive BD in the BEOL is occurred by Cu metallic filaments using a facile measurement of the temperature coefficient of resistance. The Cu metallic filaments that consist of Cu atoms mediate the uncorrelated bond breakages. The time-dependent dielectric BD lifetime is improved under the bipolar stress compared to the DC and unipolar stresses. This behavior occurs because the polarity switch during the bipolar stress interferes with the formation of stable filaments due to the occurrence of Cu atom-to-ion conversion. Understanding these phenomena can lead to practical and improved projections for future technology nodes.