Under‐bump Metallization (UBM) Control using X‐ray Fluorescence (XRF)

Energy dispersive x‐ray fluorescence is a powerful technique for measurement of film thickness as well as compositions. As chip packaging is becoming part of typical Fab process, additional multilayer stack films are used for re‐distribution of bumps and under bump metallization. These re‐distribution and under‐bump film stacks are characterized using XRF. In addition, composition of lead‐free Ag/Sn bump is also measured using small spot x‐ray fluorescence.