Effects of Co Precipitation on Si Diffusion in Ag(Co)/Si During Postannealing

Ag(5.3 at.\% Co) alloy films have been prepared on HF-cleaned Si by using DC magnetron sputtering and were then annealed in vacuum (3$\times$10$^{-5}$ Torr) to investigate the effects of Co precipitation on the material properties of the Ag(Co) films and on the reaction between Co and Si. It is proposed that upon heating above 300 $^\circ$C, Co precipitates preferentially occur at the grain boundaries of a supersaturated Ag(Co) alloy films and then grow to form the continuous Co-precipitate grain boundaries. The continuous Co-precipitates grain boundaries provide a diffusion path for Si in the Ag(Co) film, and the outdiffused Si reacts with oxygen to form a surface SiO$_2$ layer, which protects the Ag(Co) film. In addition, the diffused Si also reacts with the Co precipitates, producing Co silicide at the grain boundaries. Co silicidation at the grain boundaries influences the resistivity and retards the grain growth, resulting in a strengthening of the film. KCI Citation Count: 2