Improved Thermal Stability and Electrical Performance by Using PEALD Ultrathin Al2O3 Film with Ta as Cu Diffusion Barrier on Low k Dielectrics

Ultrathin Al2O3 films (1.3 nm or 2.5 nm) were deposited by plasma enhanced atomic layer deposition (PEALD) onto the low k (k = 2.5) material. By ALD deposition of an ultrathin Al2O3 film onto the low k surface, the thermal stability and electrical performance for the Cu/Ta/Al2O3/low k/Si system were significantly improved in comparison to those with even thicker Ta and ALD Ru/TaN layers as diffusion barrier. The effective k value of the system was not degraded by adding the ultrathin Al2O3 layer.