Impact of a TiN Capping Layer on Phase Transformation and Capacitance Enhancement in ZrO₂

Tailoring of crystalline phases and dielectric properties of ZrO2 thin films are demonstrated by capping a nanoscale TiN layer prepared by plasma-enhanced atomic layer deposition. The in-plane tensile strain induced by the TiN capping layer gives rise to the dramatic paraelectric-to-antiferroelectric phase transformation in ZrO2 and the significant capacitance enhancement up to 209%. The result is attributed to the formation of the ZrO2 tetragonal phase with the out-of-plane compressive strain due to TiN capping and the presence of interfacial TiOxNy, as revealed by nanobeam electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The results demonstrate that the as-deposited TiN capping layer can effectively modulate the dielectric properties of nanoscale thin films without any postannealing treatment, which is very beneficial for the back-end-of-line process integration and numerous applications including supercapacitors, microelectromechanical systems, energy conversion, and nanoelectronics.