Ultrathin CVD Cu Seed Layer Formation Using Copper Oxynitride Deposition and Room Temperature Remote Hydrogen Plasma Reduction

Abstract

Cu seed layers for future interconnects must have conformal step coverage, smooth surface morphology, and strong adhesion. Conformal deposition had been achieved by chemical vapor deposition (CVD), but CVD Cu films have rough surfaces and poor adhesion. In this paper, conformal, smooth, adherent, continuous, and thin (<9 nm) Cu films were made by CVD. CuON was deposited from a Cu-amidinate precursor, H2O, and NH3 at 140–180°C on Ru. Crystallites in the deposited film have either a Cu2O or Cu3N structure depending on the ratio of H2O to NH3. As-deposited CuON films have a smooth surface morphology [~0.5 nm root-mean-square (rms) roughness] and are highly conformal (>95% step coverage in 40:1 aspect ratio holes). The CuON films were then reduced with remote hydrogen plasma near room temperature to minimize agglomeration of the thin Cu films during reduction. After reduction, CuON films having a Cu2O crystal structure showed a higher density Cu film (95%) than those having a Cu3N crystal structure (84%). Both reduced Cu films had a smooth morphology (~1 nm rms roughness). Thus, deposition of a CuON film having a Cu2O crystal structure and then reduction with remote hydrogen plasma can make Cu layers that can serve as seed layers of future Cu interconnects.