Effects of nitrogen ion implantation on the thermal stability of tungsten thin films

We implanted 6×1016–3×1017 nitrogen ions/cm2 into 100 nm thick tungsten thin films with acceleration energies of 20–60 KeV. As a result, the thermal stability of N+-implanted W thin films is greatly improved from 700 to 900 °C because polycrystalline W thin films change into nanostructured films after N+ implantation. The W thin film implanted at 40 KeV and 3×1017 ions/cm2 effectively prevents Cu diffusion after an annealing at 800 °C for 30 min. When the acceleration energy and dosage are higher or lower than this optimum condition, thermal stability of the N+-implanted W film is degraded due to surface damage of Si substrate and partially nanostructured W thin film.