The evolution of multi-level air gap integration towards 32 nm node interconnects

Advanced copper interconnects need porous low-k materials to obtain low interline capacitances. A number of porous low-k integration issues have however delayed the introduction of these fragile dielectrics. Replacing the porous low-k dielectric by air is a viable alternative for future technology nodes. Air gaps are not only less prone to integration issues such as plasma damage, but they also enable extremely low capacitances since the permittivity of air is close to 1. In this paper, the evolution of the main air gap integration techniques, from micron-sized aluminum interconnect to copper interconnect for the 32 nm node are discussed in terms of integration complexity, reliability and manufacturability.