Feasibility study of 45-nm-node scaled-down Cu interconnects with molecular-pore-stacking (MPS) SiOCH films

A feasibility study was done for 45-nm-node Cu interconnects using a novel molecular-pore-stacking (MPS) SiOCH film (k = 2.45), taking electron scattering in the scaled-down Cu lines into consideration. The as-deposited MPS SiOCH film, formed by plasma polymerization of a robust six-member-ring (hexagonal) siloxane with large steric-hindered hydrocarbon side chains, has self-organized subnanometer pores. An oxidation-damage-free dual-hard-mask etching process, along with a benzocylobuten liner technique, preserved the low permittivity of the MPS film in the Cu lines, with excellent interline dielectric reliability. The line aspect ratio was also balanced to decrease not only the interconnect parasitic capacitance but also the Cu line resistivity, which is increased by the electron scattering in the narrow lines. By combining the above etching process and the line-aspect control, the feasibility of the MPS SiOCH film was confirmed with outstanding performance and excellent reliability for the 45-nm-node ultralarge scale integrations.