Understanding the role of buried interface charges in a metal-oxide-semiconductor stack of Ti/Al2O3/Si using hard x-ray photoelectron spectroscopy

Abstract

Hard X-ray photoelectron spectroscopy (HAXPES) analyses were carried out on metal-oxide-semiconductor (MOS) samples consisting of Si, thick and thin Al2O3, and a Ti metal cap. Using Si 1s and C 1s core levels for an energy reference, the Al 1s and Si 1s spectra were analyzed to reveal information about the location and roles of charges throughout the MOS layers. With different oxide thicknesses (2 nm and 23 nm), the depth sensitivity of HAXPES is exploited to probe different regions in the MOS structure. Post Ti deposition results indicated unexpected band alignment values between the thin and thick films, which are explained by the behavior of mobile charge within the Al2O3 layer.