Method of improving the bondability between Au wires and Cu bonding pads

摘要

Cu, for its rather low resistivity, will be widely used in sub-quarter micron meter ULSI devices. However, it is well known that Cu is easy to be corroded as exposed in air. In packaging of chips the bonding pads making of Cu will thus oxides. In addition, the reaction between Au-ball and Cu pads is very poor. On the other hand, a native AlOx layer, about 3-4 nm in thickness, will form as Al exposes in air; the formed layer is inert and is capable of protecting Al from corrosion. Furthermore, the reaction between Au-ball and Al was very well. Therefore, with the methods of the present invention, Al or AlCu as a glue and protection layer is implemented on Cu bonding pads for successful Au wiring.