The Evolution Of Microcraks Induced By Stress-, Electro-and Thermo-Migrations

With the rapid development of microelectronics technology, the characteristic dimensions ofintegrated circuit are decreasing gradually. The reliability of metal film interconnect undermulti-physical fields has attracted more and more attentions. The migration and evolution ofmicrocracks in metal material induced by stress field/electric field and thermal gradient is the majorfailure mode of interconnect, so the research on the migration and evolution of microcracks inducedby multi-physical fields has great significance to forecast and prevent the failure in metal filminterconnect. This paper is focused on the evolution of microcracks in metal material due tocurvature,strain,electromigration and thermal gradient induced surface diffusion.First, a simplified evolution model of intragranular and transgranular microcracks undercurvature,electric field, stress field and thermal field is established. A finite element scheme based onthe theory of surface diffusion and its weak statement is implemented and a program is developed forsimulating the evolution of two-dimensional microcracks within grains under stress field and electricfield. The reliability and accuracy of the program is proved in details.Then, the evolution of transgranular microcracks which are in a long thin elastic conductor inducedby the stress field, the electric field and the curvature of surface is simulated.The effects of the aspectratio, the magnitude and the state of the stress, the electric field and the conductor boundary on theevolution are investigated detailedly in the dissertation.Finally, a new part of thermal analysis is added to the computer program.The effects of the thermalstress which are caused by the Joule heat on the evolution of intragranular microcracks areinvestigated detailedly.