Enhanced step coverage by oblique angle physical vapor deposition

We present the use of an oblique angle physical vapor deposition (OAPVD) technique with substrate rotation to obtain conformal thin films with enhanced step coverage on patterned surfaces. We report the results of ruthenium (Ru) films sputter deposited on trench structures with aspect ratio ∼2 and show that OAPVD with an incidence angle less that 30 deg. with respect to the substrate surface normal one can create a more conformal coating without overhangs and voids compared to that obtained by normal incidence deposition. A simple geometrical shadowing effect is presented to explain the results. The technique has the potential of extending the present PVD technique to future chip interconnect fabrication