Experimental evidence for the role of electrodes and oxygen vacancies in voltage nonlinearities observed in high-k metal-insulator-metal capacitors

This work reports on voltage nonlinearities in metal-insulator- metal (MIM) capacitors using amorphous barium titanate (a-BaTiO3) thin films. It is experimentally demonstrated that voltage nonlinearity is related to the formation of a double layer at electrodes (electrode polarization mechanism). The magnitude of nonlinearities is shown to be controlled by the nature of the metal contacts (Al, Cu, Au, and Ag), as well as by the presence of oxygen during film deposition. It is thought that oxygen vacancies are the defects responsible for the nonlinear character of high-k oxide-based MIM capacitors. (C) 2007 American Institute of Physics.