High-precision heterogeneous integration based on flip-chip bonding using misalignment self-correction elements

A bonding technique, capable of sub-micron and finer alignment accuracy, has been developed for electronics-optics heterogeneous integration applications. The technique is based on the principle of misalignment self-correction using bump (convex) and hollow (concave) elements, to align one die (i.e. a chip) to another one (i.e. a substrate) during the stacking process. Conductive hollow pad and Au cone bump elements were micro machined on silicon wafers using wet anisotropic (TMAH) etching and deposition processes, respectively, and the bonding technique was examined. Repeatable bonding accuracy on the order of less than 100 nm was obtained through experimental investigation.