Excellent diffusion barrier property of amorphous NbMoTaW medium entropy alloy thin films used in Cu/Si Connect System

In this work, NbMoTaW medium entropy alloy (MEA) films with thickness of 40 nm were prepared by DC magnetron sputtering as a diffusion barrier material for Cu/Si Connect System. The microstructure and thermal property of Cu/NbMoTaW/Si and Cu/Si stacks in varies of annealing temperature (T) were studies by XRD, SEM, TEM and four-point probe measurement system. The results show that the amorphous NbMoTaW films can suppress Si inter-diffusion in Cu film when T is lower than 750 degrees C while electrical property of Cu/Si system without the barrier fails when T reaches 450 degrees C. Free of grain boundary, low diffusion coefficient value and stable structure of amorphous NbMoTaW MEA film are suggested to be the main reasons for the excellent barrier property.