Photoelectron spectroscopy study of the effect of substrate doping on an HfO2/SiO2/n-Si gate stack

Core level photoelectron spectroscopy has been used to investigate the effect of substrate doping on the binding energies of 1 nm HfO2/0.6 nm SiO2/Si films. A characteristic 0.26–0.30 nm Hf0.35Si0.65O2 silicate interface is formed between the gate oxide and the SiO2 layer with an equivalent oxide thickness of 0.5 nm. High substrate doping shifts the Fermi level upwards by 0.5 eV. An interface dipole forms giving rise to a shift in the local work function. Screening from substrate electrons is confined to the SiO2/Si interface. The principal contributions modifying the core level binding energies in the oxide are the doping dependant Fermi level position and the interface dipole strength.