Impact of interface variations on J–V and C–V polarity asymmetry of MIM capacitors with amorphous and crystalline Zr(1−x)AlxO2 films

Polarity asymmetries in J–V and C–V characteristics of symmetrical MIM capacitors with amorphous and crystalline Zr(1−x)AlxO2 films and TiN electrodes are evaluated. Physical analysis of the interface between the TiN bottom electrode and the ZrO2 layer reveals that the TiN bottom electrode undergoes enhanced oxidation during crystallization of ZrO2. Simultaneously, nitrogen is incorporated into ZrO2 near the TiN interface, and an intermixing of ZrO2 and TiO2 was identified by AR-XPS and SIMS. This asymmetry results in significant band offset differences for top and bottom electrodes of the crystalline MIM capacitor. Conduction mechanisms are correlated to amorphous vs. crystalline film properties. In addition, asymmetrical charge trapping and a higher trap density is found for crystalline Zr(1−x)AlxO2 compared to amorphous films, leading to a polarity dependence in the leakage currents.