Schottky Barrier Height at TiN/HfO_2 Interface of TiN/HfO_2/SiO_2/Si Structure

摘要

Band alignment of TiN/HfO_2 interface of TiN/HfO_2/SiO_2/Si stack is investigated by x-ray photoelectron spectroscopy (XPS). The p-type Schottky barrier height (p-SBH) is found to increase with thicker HfO_2 thickness. Since considering only the metal/dielectric interface cannot explain this phenomenon, band alignment of TiN/HfO_2 interface of TiN/HfO_2/SiO_2/Si stack is demonstrated based on band alignment of entire gate stack. Dependence of p-SBH on HfO_2 thickness is interpreted and contributed to fixed charges in gate stack, interfacial gap state charges at HfO_2/SiO_2 interface, and space charges in Si substrate. Electrical measurements of capacitor structures further support XPS results and corresponding explanation.