A method was described for calculating the volume of a saturated void, attained in a steady state when each point in a conductor line was in a state of hydrostatic pressure, and the gradient of the pressure along the conductor line balanced the electron wind. It was shown that the volume of a saturated void would either increase or decrease when the coefficient of thermal expansion of the dielectric increased and would increase when the elastic modulus of the dielectric decreased. The volume of a saturated void would also increase when porous dielectrics and ultra-thin liners were used. Under operating conditions, both thermal strains and electromigration made significant contributions to the volume of a saturated void.

Saturated Voids in Interconnect Lines due to Thermal Strains and Electromigration. Z.Zhang, Z.Suo, J.He: Journal of Applied Physics, 2005, 98[7], 074501 (8pp)