a method of electrochemically filling features on a wafer surface to form a substantially planar copper layer is provided . the features to be filled includes a first feature that is an unfilled feature with the smallest width and a second feature having the next larger width after the smallest feature . the first and the second features are less than 10 micrometers in width . the method comprises applying a first cathodic current to form a first copper layer on the wafer surface . the first copper layer has a planar portion over a first feature and a non - planar portion over a second feature . after a surface of the first copper layer is treated by applying a first pulsed current , a second cathodic current is applied to form a second copper layer on the first copper layer . the second copper layer has a planar portion over both the first and second features .