Impact of annealing on the current conduction and trap properties of CeO2/La2O3 metal-insulator-metal capacitors

Abstract

This paper focuses on the impact of annealing on the current conduction and trap states of metal-insulator-metal capacitors with CeO2/La2O3 dielectrics. Capacitance-frequency measurements identify two main trap levels (T1 and T2), characterized by an activation energy of 0.2 and 0.3 eV, respectively, and by a time constant of 1 ms and 20 μs at room temperature. The current conduction is found to be ruled by a Poole-Frenkel effect and space charge limited current under positive and negative bias, respectively. Selective annealing of CeO2 and La2O3 layers clarifies the nature of the aforementioned traps. Although providing no change in the activation energy, an additional annealing of the CeO2 and La2O3 layer is found to significantly change the trap amplitude of T1 and T2, respectively. The corresponding change of the current conduction in the region where trap assisted mechanisms play a major role is discussed.