Phase Field Modeling of Joint Formation During Isothermal Solidification in 3DIC Micro Packaging

In this paper, a computational multi-phase field approach is utilized to study the formation of the Cu/Sn/Cu micro-joint in 3-Dimensional Integrated Circuits (3DICs). The method considers the evolution of the system during isothermal solidification at 250 A degrees C for the case of two different interlayer thicknesses (5 and 10 A mu m). The Cu/Sn/Cu interconnection structure is important for the micro packaging in the 3DIC systems. The thermodynamics and kinetics of growth of eta-Cu6Sn5 and E >-Cu3Sn interfacial intermetallics (IMCs) are investigated by coupling the multi-phase field method with CALPHAD approach. The interaction of the phases is addressed by assuming a metastable condition for the Cu/Sn reacting system. The simulations start with the nucleation and rapid growth of the eta-Cu6Sn5 IMCs at the initial stage, the nucleation and growth of E >-Cu3Sn IMCs at the intermediate stage ending with the full consumption of Sn layer and the domination of E >-Cu3Sn IMCs at the later stages. In addition, comparing different diffusion rates through the grain boundary of eta phases show that their morphology is the direct consequence of balance of kinetic forces. This work provides a valuable understanding of the dominant mechanisms for mass transport in the Cu/Sn/Cu low volume interconnections. The results show that the phase field modeling is successful in addressing the morphological evolution and growth of IMC layers in the 3DIC joint formation.