Reliability Evaluation of Copper (Cu) Through-Silicon Vias (TSV) Barrier and Dielectric Liner by Electrical Characterization and Physical Failure Analysis (PFA)

The motivation behind this study is to detect barrier and dielectric liner degradation in a copper (Cu) through-silicon via (TSV) structure. The integrity of titanium (Ti) barrier and silicon dioxide (SiO2) dielectric liner are evaluated via a non-destructive electrical characterization method after being subjected to different stress tests such as high temperature storage (HTS), temperature cycling (TC) and electrical biasing. The various different stresses were either performed independently, or performed as a combination stress with electrical bias for comparison. After performing the respective stresses, capacitance-voltage (C-V) and current density-electric field (J-E) characteristics were analyzed to identify differences in its electrical characteristics. Degradation of the barrier liner may result in the migration of Cu from the Cu via into the dielectric liner. This is identified by changes observed in the inversion capacitance, as reflected in the C-V curve. Physical failure analysis (PFA) was performed on degraded structures and verified the presence of Cu in the dielectric due to barrier degradation as detected by the electrical measurement. It is suggested that barrier degradation leading to the migration of Cu into the dielectric liner can be associated to material and structural integrity which is dependent on the stress conditions. This understanding is useful in the reliability assessment of Cu TSV structures under various stress conditions, making it appropriate for future TSV degradation studies.