EM-induced mass transport at the Cu/barrier interface: a new test structure for rapid assessment at user conditions

Starting from the concept of single-damascene Blech structures, a slit-test structure was devised for the assessment of mass transport at the Cu/barrier interface. Much more compatible with standard processing, the proposed slit-test structure easily matches the sensitivity to mass transport of traditional Blech structures. Finite Element Analysis indicates the electron flow in this structure to be concentrated at the Cu/barrier interface, making it electrically very sensitive to mass transport along this diffusion path. Electrical and physical failure analysis suggest a sensitivity high enough to enable wafer-level testing of interface diffusion at user conditions.