Optimization and Characterization of the Metal Cap Layout Above Through-Silicon Via to Improve Copper Dishing and Protrusion Effect for the Application of 3-D Integrated Circuits

In this paper, different layouts of the metal cap fabricated above the through-silicon via (TSV) are experimented. Metal caps are able to counteract the force exerted by copper (Cu) protrusion, but the large Cu area of the metal cap increases the risk of the dishing effect. Dielectric apertures are inserted into the metal cap to eliminate this process concern. We found that the metal caps with dielectric apertures of smaller dimensions spread out throughout the metal cap provide more benefit to the prevention of Cu protrusion from the TSV than metal caps with dielectric apertures of larger dimensions.