Direct Measurement of Electromigration Induced Stress in Interconnect Structures

This paper reports the first direct experimental measurement of electromigration-induced stress in aluminum interconnects using a series of micro-rotating stress sensors. The build up of stress gradients in interconnect metallization concomitant with back stress have been previously investigated theoretically, but experimental verification using optical or X-ray techniques has proven more difficult. These initial results show a compressive stress gradient along the line, consistent with that predicted by conventional mass transport theory. The limited resolution of previous techniques restricts their ability to obtain a detailed characterization, whereas in principle this new technique can be scaled to the end of the International Technology Roadmap for Semiconductors. These preliminary findings suggest the present technique will provide a valuable tool for the investigation of back-end-of-line (BEOL) interconnect stress in the future