High-quality ultrathin chemical-vapor-deposited Ta 2O 5 capacitors prepared by high-density plasma annealing

Abstract

Highly reliable ultrathin low-pressure chemical-vapor-deposited (LPCVD) tantalum pentoxide (Ta 2O 5) capacitors were fabricated by using high-density plasma (HDP) annealing in N 2O at 400 °C after film deposition. It was found that HDP annealing in N 2O could significantly reduce the leakage current of Ta 2O 5 capacitors so as to produce better time-dependent dielectric breakdown characteristics than either conventional oxygen-plasma annealing or high-density plasma annealing in O 2. It was also found that HDP annealing in N 2O will not significantly increase the thickness of interface layer between Ta 2O 5 and the underlying silicon bottom electrode. Therefore, highly reliable ultrathin Ta 2O 5 capacitors can be fabricated by using HDP annealing in N 2O. 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 Ta 2O 5 films. For the N 2O HDP-annealed Ta 2O 5 films, it was found that, the main leakage mechanism was Schottky emission in low electric field and Poole–Frenkel emission in high electric field.