Air-gaps in 0.3 mu m electrical interconnections

A copper/air-gap interconnection structure using a sacrificial polymer and SiO2 in a damascene process has been demonstrated. The air-gap occupies the entire intralevel volume with fully densified SiO2 as the planar interlevel dielectric, The copper was deposited by physical vapor deposition and planarized by chemical-mechanical planarization. The Ta/Cu barrier/seed layer was deposited by physical vapor deposition; the bulk copper was electrochemically deposited. The resulting structure has an effective intralevel dielectric constant of 2.19.