Improved Thermal Stability and Electrical Performance by Using PEALD Ultrathin Al2O3Film with Ta as Cu Diffusion Barrier on Low kDielectrics

Ultrathin Al2O3films (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 Al2O3film onto the low ksurface, 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 kvalue of the system was not degraded by adding the ultrathin Al2O3layer.