Enhanced Permittivity in PEALD Al2O3/TiO2 Nanolaminates: Investigating Maxwell-Wagner and Interfacial Polarization in IDEs

This work combines precise nanofabrication methods with quasi-electrostatic finite element method (FEM) simulations to investigate possible enhancement of polarizability of localized dipoles along the interfacial planes of multilayer Al2O3/TiO2 nanolaminates. The dipole formation along these inter-material laminate boundaries is contrasted with non-localized charge movement phenomena that is typically studied in these laminates because of disparate values of the conductivity between Al2O3 and TiO2 which results in Maxwell-Wagner (MW) polarization. This MW polarization is dominant at low frequencies in metal-insulator-metal (MIM) capacitive device structures. In this work, however, electrical measurements from high-density in-plane interdigitated electrode (IDE) structures with Al2O3/TiO2 nanolaminates that are grown using Plasma Enhanced Atomic Layer Deposition (PEALD) are explored. Using FEM electromagnetic simulations suggest that the anomalous capacitance cannot be attributed to just MW effects and must also have a localized dipole effect that occurs at the interfacial boundaries. It is shown that the average relative permittivity in the vicinity of these heterogeneous interfaces (~1 nm) at a frequency of 1 kHz is extracted to be kAl2O3/TiO2 ~ 6615.