Improving the dielectric constant of Al2O3 by cerium substitution for high-k MIM applications

Process compatible high-k dielectric thin films are one of the key solutions to develop high performance metal-insulator-metal (MIM) structures for future microelectronic devices. Engineered cerium-aluminate (CexAl2-xO3) thin films were deposited on titanium nitride metal electrodes by electron-beam co-evaporation of ceria and alumina in a molecular beam deposition chamber. X-ray photoelectron spectroscopy clearly reveals that Ce cations can be stabilized in the 3+ valence state in CexAl2-xO3 up to x = 0.7 by accommodation in the alumina host matrix. Higher Ce content was observed to result in cerium dioxide segregation in cerium aluminate matrix, probably due to the chemical tendency of Ce cations to exist rather in the 4+ than in the 3+ state. Electrical characterization of the X-ray amorphous Ce0.7Al1.3O3 films reveals a dielectric constant value of about 11 and leakage current lower than 10−4 A/cm2. No parasitic low-k interface formation between the high-k Ce0.7Al1.3O3 film and the TiN metal electrode is detected.