Determination of Diffusion Boundary Layers and Copper Thickness Uniformity in Plating Tools Designed for 3-D Interconnect and Packaging Applications

Abstract

Limiting currents under mass transport limiting conditions were determined experimentally for two distinct types of electrochemical plating cells using voltammetric and chronoamperometric methods. The average limiting currents were used to estimate the thickness of the diffusion boundary layer that results from the novel cell configurations and agitation schemes. Additionally, the deposit thickness uniformity across the surface of copper plated substrates was experimentally determined and reported as the coefficient of variation (CV). Results show that optimization of the cell configurations and solution agitation within provides a thin uniform diffusion boundary layer thickness and low CVs for the metal thickness distribution indicating a uniform current distribution is achieved across the surface of the substrate.