PROJECT TITLE :

Electroless Ni Plating to Compensate for Bump Height Variation in Cu–Cu 3-D Packaging

ABSTRACT:

The feasibility of electroless Ni plating to compensate the Cu bump height variation in Cu–Cu 3-D packaging was investigated. After fabricating Cu pillar bump and Cu micro-stud structure on the high and bottom chips, respectively, Cu–Cu thermocompression bonding and then electroless Ni plating were sequentially applied and evaluated using dies shear force, daisy chain resistance, and microstructure. It is found that thermocompression bonding parameter optimization and Ar plasma surface cleaning increased the Cu–Cu bond strength. The electroless Ni plating can complete the bump height variation of one.nine $murm m$ in a chip with filling the gap between the Cu-pillar bump and Cu-micro-stud structure. Moreover, the electroless plated Ni reduced the daisy chain resistance with the increase of the contact area. The resistance of bump daisy chains when electroless Ni plating was measured to be concerning fifteenp.c not up to that obtained after Cu–Cu thermocompression bonding.