Viscoelasticity-based time-dependent stress model for a submicron aluminium interconnect

A novel model based on viscoelasticity is proposed to simulate the stress in an Al interconnect. The two-dimensional finite element method is used to solve the viscoelastic constitutive equation. The time-dependent stress relaxation of an Al film and a submicron Al line is successfully simulated using the proposed model. Excellent agreement between simulations and experiments has been obtained, which shows the effectiveness of the model. It is demonstrated that the stress distribution in Al lines when cooled from passivation temperature down to room temperature for varying cooling rates is different. It is also shown that the variation in stress affects the stress migration during subsequent heat treatment.<>