Rare-earth based ultra-thin Lu₂O₃ for high-k dielectrics

Lu₂O₃ thin film has been deposited on n-type (100) Si substrates using pulsed laser deposition (PLD). Atomic Force Microscopy (AFM) revealed a relatively smooth film surface after high temperature annealing at 900 °C with roughness root mean square (rms) value of 0.237 nm. A equivalent oxide thickness (EOT) of 1.68 nm with a leakage current density of 1 × 10^-4 A/cm² at 1 V accumulation bias and a k value of 11.6 was obtained for 4.5 nm thick Lu₂O₃ thin film deposited at room temperature followed by post-deposition anneal (PDA) at 900 °C in oxygen ambient. High resolution transmission electron microscopy (HRTEM) analysis has shown that Lu₂O₃ film remains amorphous at high temperature annealing at 900 °C with little or no observable interfacial layer. The results showed that Lu₂O₃ possesses good properties and has strong potential as an alternative high-k gate dielectric.