Endpoint detectable plating through femto-laser drilled glass wafers for three-dimensional electric interconnections

An endpoint detectable plating process to avoid over-electroplating was proposed and performed in this work. The technology was developed for a fabrication of Pyrex glass wafer with electrical feedthroughs. Thin film of gold was deposited on the glass wafer prior to a femto-second laser drilling. When a growing metal in the through-holes was contacted to the gold, a resistance between the opposite two electrodes decreases suddenly. Thus the endpoint detection was realized by in situ monitoring of applied voltage at constant current mode. After the endpoint detection, periodic reverse plating was applied to fill the through-holes uniformly. Finally, uniform copper deposition in the through-holes up to 12 aspect ratios was realized by this method.