The Suppression Breakdown induced S-NDR Mechanism for Defect-Free Filling of High Aspect Ratio Features
Daniel Josell, Thomas P. Moffat
Superconformal electrodeposition in Through Silicon Vias for multiple metal systems is summarized and shown to be explained by models based on suppressor-induced, S-shaped negative differential resistance (S-NDR). Just published results for superconformal electrodeposition of Ni in TSVs using a Watts electrolyte containing a dilute suppressing additive are detailed and the filling morphology compared to previously detailed observations of superconformal Au deposition and bottom-up Zn and Cu deposition in TSVs. Voltammetric measurements for quantifying the kinetics of metal deposition, suppressor adsorption, and impact of one on the other are shown for the different systems. Experimental dependence of the superconformal filling behavior on deposition conditions including suppressor concentration, transport and deposition potential are described. S-NDR based models are shown to capture these trends and predict the filling geometries. The results demonstrate both the generality of the S-NDR mechanism for achieving void-free of large features by electrodeposition and the power of S-NDR based models for predicting filling evolution and designing effective processes.
gold, nickel, copper, superfill, superconformal, TSV, through silicon via