New Method to Perform TDDB Tests for Hybrid Bonding Interconnects

Hybrid Bonding (HB) is progressing as the major solution for 3D integrated-circuit with pitch reduction becoming the key. Reliability needs to be studied with HB pitch reduction for possible evaluation of new failure mechanisms and modes. In this paper, we developed a new methodology to study Time-Dependent Dielectric Breakdown (TDDB) at HB level that accounts wafer-to-wafer (W2W) overlay variations. Application of this method to a 1.44 µm-pitch 3D stacked test vehicle demonstrates its accuracy. TDDB at Cu/SiO2 HB interface follows the 1/E model at low electric fields for all studied temperature suggesting that the role of Cu in breakdown is negligible. The acceleration parameter and the activation energy dependence on the electric fields are studied. The cuprous oxide layer which may act as a barrier to Cu diffusion previously highlighted at the Cu/SiO2 HB interface does not exist for Cu/SiN interfaces as evidenced by EELS study. This might explain the difference in the TDDB acceleration models between HB level and BEoL ones.