The results of bonding and stress testing of Cu/Sn-Cu bonded dice and Cu-Cu thermocompression bonded dice at 10μm and 15μm pitch in large area arrays 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. In the case of Cu/Sn-Cu, use of a mechanical key was found to improve yield. A run of 22 consecutive bond pairs was made with the mechanical key, resulting in 98 % aggregate channel yield at 10μm pitch in area arrays containing 325,632 individual bonds per die to achieve an interconnect density of 106 / cm2. SEM cross sections of Cu/Sn-Cu and Cu-Cu bonded samples and EDS analysis of Cu/Sn intermetallic compounds both before and after stress testing are presented. The results of thermal cycling and humidity-temperature testing on electrical yield and resistance are presented for Cu/Sn-Cu with underfill. Comparison of the electrical and shear test performance of Cu/Sn-Cu and Cu-Cu is made. Low temperature 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 300°C. The low temperature process may prove useful for integrating IC devices that have low thermal budgets.
Influence of isotope substitution of sodium molecule on the integral cross sections of rotational excitation in low-temperature collisions of He-Na2
