Finite Element Simulation Analysis For Copper Interconnect Reliability

With the continuous development in the Integrated Circuit technology, thecharacteristic size of the intergrate circuit continues to decrease and the reliability ofinterconnect system becomes more obvious due to the rapidly rising interconnectiondensity and number. In this paper, the phenomenon of interconnect stress migration andits failure mechanism are investigated using the finite element analysis method. Withchanging the interconnect material and its structure, the affections of the via andinterlayer dielectric on the inner-stress distribution are studied. Cavities with differentshapes are joined in the stress migration failure sensitive point in the copperinterconnection to inverstigate the affection of cavities on stress release. According tothese researches, a stress migration lifetime model is established. The results show thatthe thermal stress distribution of the interconnect system is anisotropic. The maximumstress tends to appear at the end of the via in the M1metal layer. Both increasing thediameter of the via and decreasing the constant of the interlayer dielectric will increasethe value of the maximum stress. Elliptic cylinder void is more conducive to release thestrain, especially in the migration failure sensitive area. The failure lifetime ofinterconnects decreases with increase of stress gradient, temperature coefficient andtemperature, and increases with increase of the diffusion activation energy.