Fabrication of advanced bump layer for IC power delivery

Metal interconnection in the IC technologies is more important than ever for a device performance. A robust power delivery is one of scaling challenges due to increasing operating frequencies, increasing power density, and decreasing supply voltages. Especially, the on-chip power delivery problem becomes much harder as a device scales down due to the lower voltage, higher current density, thinner metal layer, and smaller pad size. The power delivery is in general controlled by minimizing IR drop and controlling circuit noise through circuit designs. However, in this study the newly designed bumps called advanced bump layer (ABL) were evaluated to improve power delivery. The two types of ABL bumps were designed and fabricated by Cu electroplating. Bump height uniformity, surface roughness, plated structure, and sheet resistance were characterized.