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

Abstract

Ultrathin Al<inf>2</inf>O<inf>3</inf> 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)<inf>3</inf> was used as metalorganic precursor. Impacts of substrate temperature and post-annealing in O<inf>2</inf> or N<inf>2</inf> on equivalent oxide thickness (EOT), leakage current density (J<inf>A</inf>) and carbon residue of Al<inf>2</inf>O<inf>3</inf> films have been studied. It is found that post-annealing is necessary for ultrathin Al<inf>2</inf>O<inf>3</inf> 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<inf>2</inf>O<inf>3</inf> ultrathin films have larger frequency dependence and EOT of ∼1.2 nm with J<inf>A</inf> of 36 mA/cm² at V<inf>g</inf>=+1 V. AES depth profiles demonstrate that post-annealing in an O<inf>2</inf> atmosphere could effectively eliminate the carbon contamination of Al<inf>2</inf>O<inf>3</inf> films. Meanwhile, further post-annealing in N<inf>2</inf> could decrease the J<inf>A</inf> of Al<inf>2</inf>O<inf>3</inf> films to 8 mA/cm². © 2002 Elsevier Science B.V. All rights reserved.