Simulation of Copper Electrodeposition in Millimeter Size Through-Silicon Vias

Abstract

Computational predictions of copper deposition in millimeter size through-silicon vias (mm-TSV) are presented based on localized breakdown of a co-adsorbed polyether-chloride suppressor layer. The model builds upon previous work on localized Cu deposition in microscale TSV and through-holes by incorporating 3D fluid flow calculations to more effectively evaluate chemical transport of cupric ion and additives, both of which are critical to adlayer formation and disruption within the via. Simulations using potentiostatic and potentiodynamic waveforms are compared to previously reported filling experiments. Alternatively, the utility of galvanostatic control and variations in fluid flow are explored computationally. For appropriate applied potential(s) or current, deposition is localized to the via bottom, with subsequent growth proceeding in a bottom-up fashion. Selection of inappropriate current or potential waveforms, or forced convection conditions that supply insufficient cupric ion to the bottom of the via, results in prediction of voids. Simulations of deposition in via arrays (4 × 1) predict non-uniform growth across the arrays, with the passivation of individual vias associated with minor variations in convective flow and/or numerical perturbations in the simulation, that reflects the critical nature of the bifurcation process.