The influence of a structurally induced current crowding on electromigration

A slit-test structure is designed to structurally induce and accelerate current crowding in Cu damascene lines. Electromigration experiments and quantitative finite element analysis demonstrate how current crowding can substantially enhance local atomic flux along critical diffusion paths. The resulting flux divergence leads to rapid void nucleation and growth. In a comparison with traditional single damascene Cu Blech structures, the amount of current crowding is shown to be determined by the geometrical configuration of the test structure. Decreasing the barrier thickness or enlarging the height to width ratio of the Cu line leads to more pronounced current crowding and results in the acceleration of mass transport along the Cu/barrier interfaces.