The Formation and Characterisation of Lanthanum Oxide Based Si/High-k/NiSi Gate Stacks by Electron-Beam Evaporation: An Examination of In-Situ Amorphous Silicon Capping and NiSi formation

Abstract

The electrical and physical properties of La2O3 based NiSi/High-k/Si structures formed by electron beam evaporation, in-situ amorphous silicon capping and ex-situ NiSi formation are presented for the (100) and (110)Si substrate orientations. The silicon substrate orientation, (100) or (110), does not affect leakage current density or the maximum accumulation capacitance, but does have an impact on interface state densities. The interface states exhibit the electrical signature of Pbo centres for the (100)Si orientation and can be annealed in a H2/N2 ambient. The samples exhibit negligible hysteresis (<2mV). No interfacial silicon layer is observed between the La based high-k film and the silicon substrate. The extracted k value for the La2O3 based thin films is in the range 11-12 suggesting silicate formation. The work indicates an alternative approach for the examination of NiSi/high-k/Si MOS structures without ambient exposure of the high-k layer.