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

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.