Study on the interface thermal stability of metal-oxide-semiconductor structures by inelastic electron tunneling spectroscopy

Abstract

The bias polarity-dependent inelastic electron tunneling spectroscopy is employed to detect the thermal stability of the Ta–Pt∕SiO2∕Si and Ta–Pt∕HfO2∕Si structures. This work provides a direct evidence that the Fermi-level pinning of metal gates is counted for the generation of extrinsic states due to interface interaction. A Ta2O5 layer forms at the Ta–Pt∕SiO2 interface during thermal annealing whereas only an intermittent Ta–O bond is observed at the Ta–Pt∕HfO2 interface. Although the heat of formation of HfO2 is lower than that of SiO2, Si presumably diffuses into HfO2 layer and replaces Hf atoms during the high-temperature annealing.