The effects of hydrogen ambients on electromigration kinetics in A1 2% Cu thin film conductors

Surface chemical phenomena are likely to dominate the overall behavior of a system when the majority of the mass in the system is present as surface mass. Thin film interconnections of small dimensions [Large Scale and Very Large Scale Integration (LSI and VLSI)]fall into this class due to the presence of external and internal (including grain and inter-phase boundaries) surfaces. Previous investigations have strongly suggested that the presence of H ₂, presumably through surface interactions, can greatly reduce electromigration damage (EMD) leading to higher reliability for device operation. Yet, no systematic studies have been reported. We have applied the Temperature-ramp Resistance Analysis to Characterize Electromigration (TRACE) technique to examine the effect of hydrogen ambients on EMD kinetics and its effect on solid-state transport and on the void morphology of A1-2% Cu thin film conductors. Systematic variation of H ₂ ambients of varying composition and variation of the heating rate during the TRACE experiment show that the apparent activation energy for EMD remains constant while the pre-exponent changes. The results confirm a substantial improvement in EMD resistance in H ₂ containing ambients. The variation in the pre-exponential is consistent with a transport process controlled by the nucleation of voids and their subsequent growth.