High-quality ultrathin chemical-vapor-deposited Ta2O5 capacitors prepared by high-density plasma annealing

Highly reliable ultrathin low-pressure chemical-vapor-deposited (LPCVD) tantalum pentoxide (Ta2O5) capacitors were fabricated by using high-density plasma (HDP) annealing in N2O at 400 °C after film deposition. It was found that HDP annealing in N2O could significantly reduce the leakage current of Ta2O5 capacitors so as to produce better time-dependent dielectric breakdown characteristics than either conventional oxygen-plasma annealing or high-density plasma annealing in O2. It was also found that HDP annealing in N2O will not significantly increase the thickness of interface layer between Ta2O5 and the underlying silicon bottom electrode. Therefore, highly reliable ultrathin Ta2O5 capacitors can be fabricated by using HDP annealing in N2O. The leakage current mechanism was also investigated. It was found that Poole–Frenkel emission and Fowler Nordheim (FN) tunneling was the main leakage mechanism in low and high electric field, respectively, as for the deposited Ta2O5 films. For the N2O HDP-annealed Ta2O5 films, it was found that, the main leakage mechanism was Schottky emission in low electric field and Poole–Frenkel emission in high electric field.