Endpoint detectable plating through femtosecond laser drilled glass wafers for electrical interconnections

An endpoint detectable plating process to avoid over-electroplating was proposed and performed in this work. The technology was developed for fabrication of Pyrex glass wafer with electrical feed-throughs. Thin film of gold was deposited on the glass wafer prior to the femtosecond laser drilling. When the growing metal in the through-holes was contacted to the metal, 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. This technology was also applicable to the fabrication of microstructure based on electroforming.