Resistance to electromigration of purely intermetallic micro-bump interconnections for 3D-device stacking

Electromigration is a well-known root-cause for long-term reliability problems. This paper demonstrates that the resistance to electromigration is significantly increased when solder-based intermetallic bonding is used as an alternative to standard solder flip-chip interconnections. Two different intermetallic joint-types are investigated: Cu-Sn and Co-Sn. After 1000h, no failures or degradation mechanisms are observed for testing conditions (150°C and 0.63mA/¿m²) which are 10 times harsher in terms of current density compared to electromigration triggering density values for standard solder flip-chip applications (0.05mA/¿m²).