Improvement of Charge Retention in Flash Memory Devices by Very Light Doping of Lanthanum into an Aluminum-Oxide Blocking Layer

It is demonstrated that the dielectric constant of Al2O3 is significantly increased through the addition of a very small amount of La into Al2O3 followed by a high-temperature post-deposition annealing (PDA). The retention property and reliability of the charge trap flash memory devices fabricated through the proposed method are greatly improved due to the increased κ-value of the Al2O3 blocking oxide with no sacrifice of the bandgap, as well as a reduced low-field leakage component and improved dielectric relaxation effect.