The Suppression Induced S-NDR Mechanism for Defect-Free Filling of High Aspect Ratio Features

Superconformal electrodeposition in Through Silicon Vias for multiple metal systems is summarized and explained using models based on suppressor-induced, S-shaped negative differential resistance (S-NDR). Recent results for Ni are detailed, and the filling morphology is compared to previously published observations of superconformal Au, Cu and Zn in TSVs. Voltammetric measurements for quantifying the kinetics and interactions of metal deposition and suppressor adsorption are shown. Dependence of the superconformal filling behavior on deposition conditions including suppressor concentration, transport and deposition potential are described. S-NDR models based on fractional coverage of adsorbed suppressor capture experimental trends and predict the filling geometries. The results demonstrate the generality of the S-NDR mechanism for achieving void-free filling of large features by electrodeposition and the power of SNDR based models for prediction of filling evolution and process design.