Patent ID: 8003512
Filing Date: 2011-08-23
Classification: H01L

Abstract:
1. A method of fabricating an under bump metallization (UBM) structure comprising: providing a substrate having electrically conductive connections; providing said substrate in a sputtering tool; cleaning a surface of said substrate; sputter depositing at least a bilayer UBM structure of a TiW adhesion layer deposited to a thickness ranging from about 0.05 microns to about 0.3 microns followed by a Ni-based barrier layer deposited to a thickness ranging from about 0.6 microns to about 3.0 microns over said cleaned substrate surface under operating conditions that provide the resultant bilayer UBM structure with composite stress ranging from about 50 MPa to about −275 MPa; patterning said bilayer UBM structure to form bilayer UBM capture pads on said substrate surface; and joining lead-free solder connections to said bilayer UBM capture pads to provide solder joints that have reliable joint strengths after multiple reflows.