Microstructure and Stress of ULSI Cu Interconnects and Their Impacts on Electromigration
|School||Beijing University of Technology|
|Keywords||Copper interconnect lines Microstructure Stress Electromigration|
In this thesis, the microstructure and stress of ULSI in copper interconnect lines and electromigration MTF . AFM, SEM and TEM evaluation grain structure . By the recess sidewall nucleation of copper interconnect lines deposited with the increase in the linewidth , the average grain size was increased from 20 ~ 30nm 80 ~ 90nm, the grain size of the copper film is approximately 300nm; 3μm copper interconnect lines the grain size of the intermediate region is smaller than the grain size of the sidewalls ; after annealing, the grain growth of the copper interconnect lines , and the degree of grain growth is increased with the increase in the linewidth . XRD and EBSD measurements of the crystallographic orientation of the copper interconnect lines the deposited copper interconnect lines (111) texture significantly weaker than the deposited copper film ; 300 ° C , 30min annealed copper interconnect lines (111) structure enhancements ; Cu grains are obviously grew up and strain can be minimized so that the copper interconnects and copper film after a high temperature of 400 ℃ and 450 ℃ , 1h after annealing , the ( 111 ) texture did not develop . SiON and a Ta diffusion barrier layer by SIMS and AES analysis results show that the two blocking layer can effectively prevent the diffusion of copper to the SiO2 layer . The two-dimensional surface detection XRD results show that the tensile stress of the deposited copper interconnect lines , mainly by thermal stress . After annealing at 200 ℃ , copper interconnects tensile stress relaxation. The 1,2 and 4μm wide copper interconnect lines MTF increases with increasing linewidth . MTF and activation energy is higher than the deposited samples annealed copper interconnect lines grain growth and (111) texture enhanced . 4μm copper interconnect electromigration failure mainly of copper along the grain boundary diffusion; as the linewidth decreases , the diffusion of copper along the sidewall of Cu / Ta / SiO2 interfaces become electrically migration of copper interconnect lines 1 and 2 μm the main reason of the failure .