Abstract: An embodiment bump on trace (BOT) structure includes a contact element supported by an integrated circuit, an under bump metallurgy (UBM) feature electrically coupled to the contact element, a metal ladder bump mounted on the under bump metallurgy feature, the metal ladder bump having a first tapering profile, and a substrate trace mounted on a substrate, the substrate trace having a second tapering profile and coupled to the metal ladder bump through direct metal-to-metal bonding. An embodiment chip-to-chip structure may be fabricated in a similar fashion.

Abstract: A method for fabricating a through hole is disclosed. First, a conductive structure having a conductive layer and a cap layer are formed on a substrate. A patterned first photoresist layer is formed on the substrate and the conductive structure to define a pattern of the through hole. Then, a first etching process to remove the cap layer not covered by the first photoresist layer is performed until the conductive layer is exposed. The first photoresist layer is removed. A dielectric layer and a patterned second photoresist layer are formed on the substrate. Finally, a second etching process is performed to remove the dielectric layer not covered by the second photoresist layer until the conductive layer is exposed. The pattern of the second photoresist layer is the same as the pattern of the first photoresist layer.