The Electrical And Mechanical Properties Of Nanostructured Cu/Mo And Cu/W Multilayer Films

The metallic multilayer films are widely used owing to their outstanding electrical and mechanical properties with the development of microelectromechanical systems and interconnect structures.The multilayer films are composed of two or more component materials and formed by alternating deposition along the direction perpendicular to the substrate.While,the length scale effects of multilayer films will affect their performance in nanoscale.Therefore,it is meaningful to understand the electrical and mechanical properties of nanostructured multilayer films.In this work,nanostructured Cu/Mo and Cru/W multilayer films with different modulation periods from 10nm to 150nm were prepared by magnetron sputtering technology.The X-ray diffractomer,atomic force microscope and transmission electron microscopy,four point probes measurement,nanoindentation and micro-force test system were used to examine the microstructure and properties of nanostructured multilayer films.The effect regularity and mechanisms of modulation period on electrical and mechanical properties of nanostructured Cu/Mo and Cu/W multilayer films were investigated in this paper.Finally,the best combination of mechanical and electrical properties can be achieved by artificially tailoring the modulation period of multilayer films.Cu/Mo multilayer films are consisted of Cu and Mo phases and the Cu/W multilayer films are consisted of Cu and W phases.With decreasing of modulation periods,the grain sizes are decreased.The surfaces of multilayer films show good crystallization,and the particles are uniform.The films are grown as a Volmer-Weber mode.The roughnesses are all in nanoscale.Moerover,the interfaces are relatively straight,and the modulation structures of the films are clearly.The resistance of nanostructured Cu/Mo and Cu/W multilayer films are length scale-dependent.The resistances of nanostructured Cu/Mo multilayer films are increase first and then decrease.The maximum value of the resistivity is achieved when the modulation period is 25nm.The resistances of nanostructured Cu/W multilayer films increase with decreasing modulation period.The effect of modulation periods on the resistance conforms to the FS-MS transmission model.The resistances of the films are mainly affected by both grain-boundary scattering and interface-boundary scattering.The changing regularity of the resistance of the films with different modulation periods conforms to the FS-MS transmission model.The grain size and resistance of nanostructured Cu/Mo and Cu/W multilayer films have no significant change after annealing at 400??600? for 1h,which indicated that the thermostability of multilayer films is good.The nanoindentation hardness,young's modulus and yield strength of nanostructured Cu/Mo multilayer films exhibit the trendency of increase first and then decrese with the decreasing of modulation period.The hardness,modulus and strength of nanostructured Cu/W multilayer films increase with decreasing of modulation period.The results can be interpreted by the Hall-Petch model.The interface and grain boundary blocking the movement of dislocation make a significant contribution to the mechanical properties of the films.The best combination of mechanical-electrical properties of nanostructured Cu/Mo and Cu/W multilayer films are achieved when the modulation period is 100nm.