Abnormally enhanced dielectric constant in ZrO2/Ta2O5 multi-laminate structures by metallic Ta formation

Thin ZrO2/Ta2O5 multi-laminate films were grown by atomic layer deposition and the relation between their dielectric and chemical properties was investigated. Metallic Ta is strongly reduced at the interface between ZrO2 and Ta2O5, probably during the deposition of the ZrO2/Ta2O5 laminated films. The tetragonal crystal phase is optimally stabilized in these ZrO2/Ta2O5 multi-laminate layers at a Zr/Ta cycle ratio during deposition of 5/2, corresponding to a Ta content in the films of approximately 3.7%. The dielectric constants of these ZrO2/Ta2O5 films are abnormally high, with values of 70-100 measured for films that are 7.5-12 nm thick. Possible explanations for this enhancement are discussed. (C) 2015 Elsevier B.V. All rights reserved.