Nitrogen distribution and oxidation of HfO_xN_y gate dielectrics deposited by MOCVD using [(C₂H₅) ₂N]₄Hf with NO and O₂

Ultra-thin HfO_xN_y gate dielectric films were deposited by pulse-mode metalorganic chemical vapor deposition (MOCVD) with [(C₂H₅)₂Hf (TDEAH) and either NO or O ₂ as oxidants. Nitrogen incorporation was studied by jc-ray photoelectron spectroscopy (XPS) and spatially-resolved elemental profiles were obtained by scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) and energy dispersive x-ray spectroscopy (EDS). The results indicate that nitrogen is incorporated throughout the high-k film with a higher concentration in the interface layer between the deposited layer and the Si(100) substrate. The concentration of nitrogen is increased in both layers by using NO instead of O₂ as the oxidant. The N in the deposited and interface layers can be replaced by oxygen during oxygen ambient annealing at temperatures above 500°C. Films with 8 at.% nitrogen remain amorphous following vacuum annealing at temperatures up to 800 °C. By encapsulating vacuum-annealed films with amorphous Si from an e-beam evaporator prior to removal from the cluster tool, it was possible to reduce the thickness of the interface layer upon air exposure to the 0.5 nm range.