| abstract |
An apparatus comprises a first semiconductor chip including a first substrate, a plurality of first inter-metal dielectric layers and a plurality of first metal lines, a second semiconductor chip having a surface in contact with a surface of the first semiconductor chip, wherein the second semiconductor chip comprises a second substrate, a plurality of second inter-metal dielectric layers and a plurality of second metal lines and a conductive plug coupled between the first metal lines and the second metal lines, wherein the conductive plug comprises a first portion over a first side of a hard mask layer and a second portion over a second side of the hard mask layer, wherein the hard mask layer is a ring-shaped layer, and wherein the conductive plug is formed in a center opening of the ring-shaped layer. |