Ultrasonic bondability and antioxidation property of TiN/Ag metallization on Cu PAD

Copper interconnect has become the only one option for the semiconductor manufacturing under 110 nm. However, there are some problems to be solved in the copper interconnect, especially the bad bondability due to the oxidation of the copper. In this paper, TiN/Ag metallization was fabricated as the protective layer of copper pad by magnetron sputtering. The amorphous TiN film as the barrier layer to prevent copper atoms diffusing from the copper pad to the surface, and the crystalline Ag film as the bonding layer to enhance the bond abilities. The TiN/Ag metallization was characterized by AFM, XPS, XRD and SEM, respectively, and then the ultrasonic bondability of Au wire and antioxidation property of the metallization were measured. The shear test of the Au ball bond was performed by micro-force tester. Ultrasonic bondability test shows that TiN/Ag metallization as the copper chip protective layer has good bonding performance. The bondability and shear strength of the Au ball bond on the metallization increased with the temperature increase from the room temperature to 180°C. The TiN/Ag metallization has 100% bondability at 180°C, and the shear failure occurred at the interface of Ag film and Au ball bond. High temperate storage test shows that TiN/Ag metallization has better antioxidation property than the Ag film, since the amorphous TiN layer plays an excellent role of diffusion barrier.