Molecular Dynamics Simulation Study Of Deposition And Nanoindentation For Cu Thin Film On Ti Surface

Cu nanofilm with low resistivity,high atomic mobility and oxidation resistance have replaced Al as the next generation interconnect material for electronic devices.However,Cu thin film will react with Si substrates in microelectronic devices to form copper silicon compounds,which reduces the reliability of Cu thin film as interconnect materials.As a suitable adhesion layer and barrier layer,Ti can enhance the adhesion between Cu thin film and Si substrates and block the diffusion between Cu and Si.Currently,research on Ti surface Cu thin film mainly focuses on traditional experimental methods.In order to observe the growth process and deformation behavior of Ti surface Cu thin film from an atomic scale and optimize the application performance of Cu thin film,in this paper,we employed molecular dynamics method to investigate the physical vapor deposition(PVD)process of Cu thin film on Ti substrate,and conducted a molecular dynamics simulation study on the nanoindentation of the Cu thin film after the deposition was completed.The PVD deposition model of Cu thin film on Ti surface was established,and the effects of incident energy and incident angle on Cu deposition into thin film were investigated.The research results indicate that incident energy is a critical factor in determining the growth mode of Cu thin film during deposition.Specifically,at an incident energy of 0.1 e V,Cu thin film growth occurs in an island shape,while increasing the incident energy to 10 e V results in the formation of a layered structure.In contrast,the incidence angle has less influence on the growth pattern of the Cu thin film,but when the incidence angle is increased to 45°,the surface of the Cu thin film appears to be "grooved",which reduces the quality of the thin film.Increasing the incident energy reduces the surface roughness of Cu thin film,and the root mean square roughness of Cu thin film is 1.11 ? when the incident energy is 10 e V.Increasing the incident angle slightly increases the surface roughness of Cu thin film,and the root mean square roughness of Cu thin film surface increases from 1.78 ? to 3.03 ? as the incident angle increases from 0° to 45°.Molecular dynamics simulation of nanoindentation was conducted on the Cu thin film on the Ti surface after deposition,and the deformation behavior of Cu thin film was analyzed under different indenter velocities(1 m/s,20 m/s and 40 m/s).The research results indicate that the higher indenter velocity leads to more amorphous regions inside the Cu thin film.During the nanoindentation process,dislocations are typically formed first beneath the indenter.As the indentation depth increases from 0.6 nm to 2.6 nm,Shockley incomplete dislocations slip and rapidly proliferate inside the Cu thin film.There are also Stair-rod dislocations and a few Hirth,Frank and Perfect dislocations in Cu thin film.As the velocity of the indenter increases,the indentation load also increases at the same depth,which promotes the formation and pile-up of dislocations inside the Cu thin film,leading to the hardening of the thin film.In addition,the amount of Cu thin film surface buildup gradually decreases as the indenter speed increases,which helps to reduce the impact of atomic stacking on the mechanical properties measurement results.