The Analysis And Research Of Cu Interconnection Failure

This paper aims to study the copper interconnect reliability issues of ULSIcircuits，including electro-migration failure and stress-migration failure. The paper usesexperimental and theoretical methods, through the electro-migration failure experimentand the critical length effect to study the electro-migration failure. The paper buildsfinite-element models by verifying interconnect layers and void positions andgeometries. The influences of the stress distribution have been studied through thecomparison between different structures of the copper interconnect. The results of thestudy indicate that a critical length effect exists in the electro-migration failure. Failureshappen when the interconnect length is longer than the critical length. Throughimproving the interface characteristics and related early processes, the electro-migrationfailure can be effectively restrained. Due to the existence of the residual thermal stress,vacancies exist in the metal interconnect and nucleate towards the direction of the stressgradient. As the voiding diameter increases, the stress and the stress gradient decreasecontinuously, and the growth rate of the voiding decreases too.