Redistribution Lines Having Nano Columns and Method Forming Same

A method includes forming a seed layer over a first conductive feature of a wafer, forming a patterned plating mask on the seed layer, and plating a second conductive feature in an opening in the patterned plating mask. The plating includes performing a plurality of plating cycles, with each of the plurality of plating cycles including a first plating process performed using a first plating current density, and a second plating process performed using a second plating current density lower than the first plating current density. The patterned plating mask is then removed, and the seed layer is etched.