Periodic pulse reverse copper filling for void-free through-via filling

In this work, a study of TSVs electrodeposition filling by the periodic pulse reverse current was performed in a plate solution without additives. A void-free filling was obtained at a lower current density while a hollow or seam structures were obtained at a higher current density. A 'bottom-up' growth mode could be realized at the lower current density. The current distribution uniformity inside a via was expressed by a function of the Thiele modulus, μ. The Thiele modulus was calculated to be less than 1 at a lower applied current density and more than 1 at higher applied current density, which corresponded to a void-free filling and void-formation filling respectively.