Superconformal Bottom-up Gold Deposition in High Aspect Ratio through Silicon Vias

Abstract

This work demonstrates gold filling of 56 mm tall, annular Through Silicon Vias (TSVs) using a mechanism that couples suppression breakdown and surface topography to achieve controlled bottom-up deposition. The chemistry, a sulfite electrolyte containing a dilute suppressing additive, and processes are fully detailed. The impact of deposition potential and additive concentration on the filling of the patterned features is presented. Voltammetric measurements on planar substrates, including the impact of rotation rate and suppressor concentration on the rate of metal deposition and potential of suppression breakdown, are used to quantify the interplay between metal deposition and suppressor adsorption. The derived kinetics are then used with the S-shaped negative differential resistance (S-NDR) mechanism for superconformal deposition to quantitatively predict the observed bottom-up filling in the TSVs as well as understand the spatial variation of deposit microstructure. The predictions capture the experimental observations. This work extends understanding and application of the additive-derived S-NDR mechanism, including previous demonstrations of superconformal filling of TSVs with nickel, cobalt, zinc and copper.