Interface Optimization and Performance Enhancement of Er₂O₃-Based MOS Devices by ALD-Derived Al₂O₃ Passivation Layers...

In this paper, the effect of atomic layer deposition (ALD)-derived Al₂O₃ passivation layers and annealing temperatures on the interfacial chemistry and transport properties of sputtering-deposited Er₂O₃ high-k gate dielectrics on Si substrate has been investigated. X-ray photoelectron spectroscopy (XPS) analyses have showed that the ALD-derived Al₂O₃ passivation layer remarkably prevents the formation of the low-k hydroxides generated by moisture absorption of the gate oxide and greatly optimizes the gate dielectric properties. Electrical performance measurements of metal oxide semiconductor (MOS) capacitors with different gate stack order have revealed that the lowest leakage current density of 4.57 × 10^-9 A/cm² and the smallest interfacial density of states (Dit) of 2.38 × 10¹² cm^-2 eV^-1 have been achieved in the Al₂O_3/Er₂O₃/Si MOS capacitor, which can be attributed to the optimized interface chemistry. Further electrical measurements of annealed Al₂O_3/Er₂O₃/Si gate stacks at 450 °C have demonstrated superior dielectric properties with a leakage current density of 1.38 × 10^-9 A/cm². At the same, the leakage current conduction mechanism of MOS devices under various stack structures is systematically investigated.