Diffusion boundary layer studies in an industrial wafer plating cell

Abstract

Linear Sweep Voltammetry and Chronoamperometry methods are described that measure Limiting Current in a dilute solution within an industrial wafer plating cell. Copper deposition in a dilute solution, under mass-transfer-limited conditions, is utilized to study the distribution profile of the mass transfer diffusion layer across the wafer surface. We show that a shear plate fluid agitation mechanism is capable of generating a thin (i.e. < 10μm), spatially uniform and non-periodic boundary layer across the entire wafer surface. We expect that thin boundary layer deposition will prove to be beneficial in MEMS, flip-chip bumping, and WL-CSP applications.