Current crowding effect on copper dual damascene via bottom failure for ULSI applications

Reliability of interconnect via is increasing an important issue in submicron technology. Electromigration experiments are performed on line/via structures in two level Cu dual damascene interconnection system and it is found that wide line/via fails earlier than the narrow line/via. Atomic flux divergence based finite element analyses is performed and stress-migration is found to be important in the failure rate behavior observed. Semi-classical width dependence Black´s equation together with the finite element analysis revealed that the difference in the time to failure is due to the much larger average current density along the interface between the line and via for the wide line/via structure, and good agreement is obtained between the simulation and experimental results.