The impact of trench width and barrier thickness on scaling of the electromigration short - Length effect in Cu / low-k interconnects

The mechanisms involved in the reduction of electromigration failure times of Cu/low - k interconnects with scaling depend on the conductor length. Long lengths are impacted primarily by changes in interconnect critical geometry and Cu microstructure. Short lengths exhibit an additional dependence on the mechanical properties of interconnects. Consequently, trench width and barrier thickness affect electromigration failure of short - length conductors by changing the critical current density, j_c. With technology progression barrier thickness reduces faster than trench width, leading to an overall lowering of j_c. Continued scaling will result in a faster rate of failure time reduction for short - lengths than long - lengths, diminishing improvements in circuit currents available at short lengths. Incorporation of ultra-thin (~10Å) barriers furthers increase the rate of reduction of j_c.