Diffusion behavior of dual capping layers in TiN/LaN/AlN/HfSiOx/Si stack

The diffusion behavior and interlayer interactions in the LaN/AlN dual capping layers of TiN/LaN/AlN/HfSiOx/Si stacks are investigated. Depth profiling and chemical state analysis performed after partial removal of the TiN gate indicate that Al-O replaces Al-N forming an Al-O dipole layer between the TiN and high-k layer after annealing. Meanwhile, La diffuses into HfSiOx and the La-based dipole is controlled by suppression of O diffusion to the bottom layer. Our results reveal that the properties of the TiN/LaN/AlN/HfSiOx/Si stack can be improved significantly by the dual capping layers.