Impact of Forming Gas Annealing and Firing on the Al2O3/p-Si Interface State Spectrum

The interface-state spectrum at the Al2O3/p-Si interface is investigated by Deep-Level Transient Spectroscopy on Metal-Oxide-Semiconductor (MOS) capacitors. It is shown that a Forming Gas Anneal or firing step leads to a significant reduction of the density of interface states (Dit). At the same time, it is found that the peak activation energy of the Dit distribution lowers towards the valence band of Si. From a comparison with the DLTS data on 5 nm SiO2 MOS capacitors, it is concluded that the same type of states is observed for both dielectrics, implying that the interface properties are determined by the thin interfacial SiO2 layer.