Successful dual damascene integration of extreme low k materials (k < 2.0) using a novel gap fill based integration scheme

A novel scheme known as the etch back/gapfill (EBGF) integration scheme was used to successfully generate multi-level dual damascene structures using intermetal dielectric (IMD) materials with k less than 2.0. It is shown that the ultra low keff values can be achieved with an EBGF scheme, without having to resort to partial air gap structures which could potentially have significant mechanical and electrical reliability risks. New CMP processes were developed to prevent the degradation and dishing of the porous IMD materials used in this integration scheme. The dense support dielectric material underneath the metal lines provides mechanical reinforcement with a minimal increase in the overall capacitance of the BEOL interconnect.