High performance Al dual damascene process with elevated double stoppers

An integrated Al dual damascene process which can simultaneously realize smaller interconnect wire resistance variations and reduced wire-to-wire capacitance increase is presented. The main feature of the process is using SiN etch stoppers which are well removed from the corners of the wires. Compared to the conventional damascene structure with SiN etch stoppers directly above and below the wires, the wire-to-wire capacitance increase due to the presence of SiN is reduced by half in the new process. By integrating the process with a newly developed low resistance Al reflow sputter process using a Nb liner, it is confirmed that excellent electrical characteristics are obtained for the dual-damascene wires and vias.