TaN-TiN binary alloys and superlattices as diffusion barriers for copper interconnects

Binary alloys and superlattices of TaN-TiN thin films were grown on Si(100) substrates with a TiN buffer layer using pulsed laser deposition. A special target assembly was used to manipulate the concentrations of these binary component films. The 60% TaN resulted in a TaN (3 nm)/TiN (2 nm) superlattice, while 30% and 70% TaN generated uniform Ta_xTi_1−xN alloys. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) confirmed the single-crystalline nature of these films. Four-point probe resistivity measurements suggest that these alloy and superlattice films have a lower resistivity than pure single-crystalline TaN films. The Cu-diffusion characteristic studies showed that these materials would have the potential as high-temperature diffusion barriers for Cu in ultra-large-scale integration technology.