Growth and characterization of Al2O3 gate dielectric films by low-pressure metalorganic chemical vapor deposition

Ultrathin Al2O3 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 O2 or N2 on equivalent oxide thickness (EOT), leakage current density (JA) and carbon residue of Al2O3 films have been studied. It is found that post-annealing is necessary for ultrathin Al2O3 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 Al2O3 ultrathin films have larger frequency dependence and EOT of ∼ 1.2 nm with JA of 36 mA/cm2 at Vg = + 1 V. AES depth profiles demonstrate that post-annealing in an O2 atmosphere could effectively eliminate the carbon contamination of Al2O3 films. Meanwhile, further post-annealing in N2 could decrease the JA of Al2O3 films to 8 mA/cm2.