New breakdown mechanism investigation: Barrier metal penetration induced soft breakdown in low-k dielectrics

A Soft Breakdown (SBD) phenomenon happening in porous low-k dielectrics during time dependent dielectric breakdown measurements was investigated. The early formation of local conductive paths was identified by monitoring leakage currents and capacitance data in the SBD phase. The nature of this conductive path was demonstrated to be related to intrinsic dielectric degradation. By comparing samples with different process conditions, we found that barrier metal penetration is an important root cause of SBD initiation. Our study of the voltage and temperature acceleration of the SBD phenomenon shows that these acceleration factors, m=22 and Ea=0.2eV, are at a reasonable level. However, further investigations on large size devices illustrate that the difference in barrier metal penetration depth between different samples could lead to a large decrease of Weibull slopes and degrade the overall reliability performance. Therefore, innovations of metal barrier deposition on porous low-k dielectrics to avoid barrier metal penetration are required for advanced technology nodes.