Leakage mechanisms and dielectric properties of Al2O3/TiN-based metal-insulator-metal capacitors

We characterized thin Al2O3 dielectrics with TiN electrodes in a three-dimensional, high-aspect-ratio, metal–insulator–metal capacitor structure. Transmission electron microscopy images did not reveal any interfacial layer(s) or intermixing of the films. This was confirmed by series capacitance analysis. Extensive electrical characterization indicated a well-behaved dielectric response. Time and frequency domain measurements did not show any significant dielectric relaxation. Charge transport was controlled by a direct tunneling mechanism in the field range of 1.5 to 6 MV/cm for a 50 Å film. The Fowler–Nordheim tunneling mechanism dominated the high field range (>6 MV/cm for a 50 Å film), and the leakage currents became independent of dielectric thickness. The electron tunneling effective mass was found to be 0.2 me.