Conductive bump structure and method of manufacturing the same

Abstract

The embodiment of the present disclosure provides a conductive bump structure and a preparation method thereof. The method comprises the following steps: providing a wafer, the surface of the wafer is provided with a passivation layer and a pad; forming a UBM layer electrically connected with the pad on the surface of the wafer; adopting a step-by-step electroplating process to sequentially stack and form a first metal copper layer, a second metal copper layer and a third metal copper layer on the UBM layer to form a metal copper bump electrically connected with the pad; performing chemical plating on the surface of the metal copper bump to form a first protective layer wrapping the surface of the metal copper bump; performing chemical plating on the surface of the first protective layer to form a second protective layer wrapping the first protective layer to form a conductive bump structure. The gradient electroplating is adopted to obtain a copper bump with gradientized internal grain structure and low overall internal stress, and the reliability of the copper bump is improved. The copper bump is electroplated first, and then chemical plating is performed, so that the nickel / gold protective layer uniformly covers the top and all sides of the copper bump, complete sealing in three-dimensional directions is achieved, and copper oxidation is completely eliminated.

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