Via structure and process for forming the same

摘要

Via structure and process flow for interconnection in a semiconductor product. A bottom metal layer is provided to represent a connection layer in the semiconductor product. An isolation layer on the bottom metal layer comprises a via hole exposing a portion of the bottom metal layer. The via hole comprises a sidewall and a bottom. A first barrier metal layer is disposed on the sidewall of the via hole, but not on the bottom of the via hole. A metal under-layer is formed on the bottom of the via hole and on the first barrier metal layer. A second barrier metal layer is formed on the metal under-layer. A metal fill layer fills the via hole. A lattice mismatch between the metal under-layer and the second barrier metal layer is less than about 5%.