Growth and characterization of Al 2O 3 gate dielectric films by low-pressure metalorganic chemical vapor deposition

Abstract

Ultrathin Al 2O 3 films have been deposited on n-Si substrates by low-pressure metalorganic chemical vapor deposition (MOCVD) as gate dielectrics for next generation MOSFET applications. Al(acac) 3 was used as metalorganic precursor. Impacts of substrate temperature and post-annealing in O 2 or N 2 on equivalent oxide thickness (EOT), leakage current density ( J A) and carbon residue of Al 2O 3 films have been studied. It is found that post-annealing is necessary for ultrathin Al 2O 3 films to obtain good electrical properties. The EOT shows slight deposition temperature dependence and the lowest EOT value with ∼0.8 nm is obtained at 600 °C. Typical Al 2O 3 ultrathin films have larger frequency dependence and EOT of ∼1.2 nm with J A of 36 mA/cm 2 at V g=+1 V. AES depth profiles demonstrate that post-annealing in an O 2 atmosphere could effectively eliminate the carbon contamination of Al 2O 3 films. Meanwhile, further post-annealing in N 2 could decrease the J A of Al 2O 3 films to 8 mA/cm 2.