Impact of Pulse Parameters on Current Distribution in High Aspect Ratio Vias and Through-Holes

Abstract

A quasi one-dimensional current-distribution model is used to explore the impact of pulse-reverse plating parameters on throwing power when depositing copper into high-aspect-ratio through-holes or vias. The optimum waveform depends on a number of parameters, including bath composition, fluid flow, time-average plating rate, and via or through-hole dimensions. Understanding whether spatial variations in plating rate are caused primarily by electrical potential variations or by concentration variations is crucial to the design of a waveform. Pulse-reverse plating frequently provides greater improvements in throwing power than on-off pulse plating. Furthermore, employment of a pulse-reverse waveform can reduce the sensitivity of the throwing power to diffusion-layer thickness, a practically useful result when it is difficult to transfer a fluid-mixing method from the laboratory to manufacturing.