Band Lineup Issues Related with High-k/SiO_2/Si Stack

摘要

Band lineups of high-k dielectrics such as atomic layer deposition (ALD) grown HfO_2 and Al_2O_3 with different thicknesses on SiO_2/Si stack are investigated by X-ray photoelectron spectroscopy (XPS). The band offsets at HfO_2/SiO_2, Al_2O_3/SiO_2 and SiO_2/Si interfaces are found to vary with physical thickness of high-k dielectric. Concepts of gap states and charge neutrality level (CNL) are employed to discuss band lineup of high-k/SiO_2/Si stack. The observed XPS results are interpreted and attributed to lower CNLs of HfO_2 and Al_2O_3 than SiO_2/Si stack, indicating feasibility of gap state based theory in investigating band lineup of oxide/semiconductor and oxide/oxide heterojunctions.