Reliability and ultra-low temperature bonding of high density large area arrays with Cu/Sn-Cu interconnects for 3D integration

The results of lifetime testing of Cu/Sn-Cu eutectic bonded dice at 10μm pitch in large area arrays of 325,632 interconnects are shown. The interconnect bonding process (pressure and temperature) required for the formation of low resistance (~100 mΩ), high yielding (99.99% individual bond yield), and reliable interconnects is described. The effects of thermal cycling on electrical yield and resistance are presented. Ultra-low temperature eutectic bonding (at 210°C, below the melting point of tin) is demonstrated to produce high electrical yield, high shear strength and similar intermetallic compound formation to devices bonded at the standard 300°C temperature. Electrical results, shear test results, SEM cross sections and EDS analysis comparisons are presented. The ultralow temperature process may prove useful for integrating IC dice that have low thermal budgets.