Effect of Valence State of Doping Materials on Resistance Switching Characteristics of Doped HfO2 Films

In this work, the effect of valence state of doping materials on the resistance switching characteristics of HfO2 films was investigated in conjunction with an analysis of the film chemical bonding states. TiN/as-grown and doped HfO2/Pt metal-insulator-metal (MIM) stacks were fabricated using HfO2 films with Mg, Al, and Nb doping materials sputtered by reactive dc magnetron co-sputtering. From XPS analysis, the doping concentration of Mg, Al, and Nb doped HfO2 films was 2.2%, 2.9%, and 2.6%, respectively. The resistance switching characteristics of the MIM stacks were examined with a study on the physical properties such as the microstructure and chemical bonding of doped HfO2 films. The microstructure of as-grown HfO2 film and Mg, Al, Nb doped HfO2 films shows the monoclinic and tetragonal structure. And the concentration of non-lattice oxygen of as-grown and doped HfO2 films was related to resistance switching characteristics. TiN/as-grown and doped HfO2/Pt stacks showed typical bipolar resistance switching characteristics after electro-forming. In general, a large number of grain boundaries and high concentration of non-lattice oxygen lead to high conductivity of the metal oxides. The resistance switching characteristics was influenced on change of grain boundaries and the concentration of non-lattice oxygen. From these findings, we estimated that the controlling of microstructure and the chemical bonding states influenced the resistance switching characteristics of doped HfO2.