Ultra-High Strength Cu-Cu Bonding under Low Thermal Budget for Chiplet Heterogeneous Applications

In this study, using metal passivation (Au or Pd), chip-level Cu to Cu bonding with 15×15 μm
²
bump size and 15 μm bump pitch has been achieved at 180°C for 30 seconds under the atmosphere. The good bonding results have been carefully validated by analyzing SEM, TEM, EDS, and shear test. Despite the small bonding pad and fine pitch, the high bonding strength (27.9 MPa) can be still obtained, showing the high feasibility of this bonding structure for chiplet heterogeneous integration.