Damage Process of Polycrystalline LSI Conductor Due to Atom Migration Induced by Electric Current and Stress

Abstract

Electric current inducesatom transport along grain boundary (GB) and interface (IF) in an LSI conductor and it istermed ‘‘electromigration (EM)’’. The atom flow and the constraint of deformation bring about the stress on the GB, which induces another atom flow (stress-induced migration: SM) under no external load. The functional for the EM and SM in a polycrystalline material is derived where the deformation field and the atom flux are calculated by minimizing the functional on the basis of the variational principle. A numerical simulation method of damaging process is proposed, and the mechanism and mechanics of cavity growth isanalyzed by the method under an electric current without external load. The results obtained are as follows. (1) The efflux of atoms at the cavity tip is governed by the stress evoked by the electric current (SM), while the atoms are carried far away by the EM. (2) The GB/IF network strongly influences the atom flow near the cavity and acceleratesthe cavity growth. (3) The high IF diffusivity activates not only the atom transport along the IF but also those along the GBs connected with it. The cavity growth isaffected by the accelerated atom flow.