Degradation mechanisms and microstructure evolution of TGV-Cu vertical interconnects in glass wafer under high-temperature aging

This study investigates the failure mechanisms and microstructural evolution of through glass via-copper (TGV-Cu) interconnections under high-temperature storage conditions. Under aging conditions, the glass/Ti/Cu interface coarsens, leading to the formation of irregular voids and microcracks at the Cu/Ti interface that propagate under thermal stress and evolve into through-thickness cracks. The diffusion rate of Ti decreases as the system approaches thermodynamic equilibrium. Cracks predominantly propagate along the sidewalls of the TGV-Cu interconnections in a transgranular manner due to shear stresses at the glass/Ti/Cu interface. The grain size of TGV-Cu increases from an initial average of 3.12 μm to 9.97 μm, with a heterogeneous distribution. The initial preferred orientation is < 001>, but after aging for 50 h, shifts toward <101> and <111> directions, before reverting to <001> with further aging. Nanoindentation results indicate that the elastic modulus and hardness decrease initially, then increase during thermal aging, although overall performance remains lower than in the initial state. These findings provide insights into the integrity and lifetime prediction of TGV-Cu interconnections, aiding in the reliability design of glass-based electronic packaging systems.