Dewetting is a nontrivial challenge in thermal and chemical processing of thin films. Conventional methods in dewetting prevention concentrate on interfacial modification and surface capping. The first approach suppresses dewetting by placing a new chemical species at the interface between films and substrates to decrease their interfacial energy; the later one achieves the goal through exerting additional tensile strain on the film with a capping layer.
Here we prevent dewetting by doping via ion implantation. Silicon atoms of different doses are used at dopant-level concentrations (1, 2, 4×1015 atoms/cm2) implanted into 100 nm Ag thin films grown at room temperature directly on single crystal sapphire substrates by high-vacuum sputtering (~10-6 torr). SEM, TEM, AFM and Raman are used to characterize film morphology before or after vacuum annealing treatment (803K, 30 - 1300 min, 10-4 torr). The interfacial energy of the Ag film during heat processing is calculated based on Miller’s close-packed hexagonal cylinder model. The influence of dopant ions on grain growth is measured as well as simulated according to Cahn’s solute drag theory.
It is found that 1014cm-2 Si4+ ions are sufficient to stop 100nm-thick Ag film from rupture even after 21 hours annealing, which can be attributed to those additional ions successfully retard Ag grain growth during heating resulting from their solute drag effects. Downsized Ag grains significantly decrease grain diameter-to-height ratio of the film, thereby enabling the continuous Ag film to possess a lower interfacial energy than the discrete Ag islands and to maintain its initial shape. Furthermore, a simulation of the solute drag effect on grain growth successfully matches our experiments, proving that small amounts of dopants are capable of decelerating grain growth and shrinking average grain size and thus preventing the thin film dewetting. These results show the potential for novel contact processing for advanced semiconductor device applications.