Charge trapping at low injection currents in (TiN, Mo, Pt)/Ta2O5:Hf/SiO2/Si structures

Samples investigated in this work contain Hf-doped layers of Ta₂O₅, i.e. the mixture of two most favorable high-k materials, which proved appropriate characteristics for application in DRAMs and MOSFETs. The influence of the top electrode material, with different work functions, on the electrical properties of MIS structures is of particular interest and was studied in this work. Here we confirmed that the presence of interface states causes frequency dispersion of C-V characteristics, but still the negligible hysteresis indicates very low slow states density of the order of 10¹⁰ cm^-2. Another effect observed here is due to the nature of the gate electrodes. It is observed only in the case of high-work-function metal, when trapping of charges in the emptied positive traps in doped Ta₂O₅ occurs, case that was previously observed in pure Ta₂O₅. Here we have determined the parameters of the traps responsible for this effect.