Adhesion layer-bottom electrode interaction during BaxSr1-xTiO3 growth as a limiting factor for device performance

Changes in bottom electrode morphology and adhesion layer composition upon deposition of BaxSr1-xTiO3 (BSTO) at elevated temperatures have been found, which have a negative impact on acoustic wave resonator device performance. The difference between nominal and actual adhesion layer composition are explained by grain boundary diffusion of Ti or W and their oxidation by in-diffusing oxygen, which leads to an increased interface roughness between the Pt bottom electrode and the BSTO. It is shown, that room-temperature deposited TiO2 diffusion barriers fail to protect against Ti oxidation and diffusion. Also W adhesion layers are prone to this phenomenon, which limits their ability to act as high temperature resistant adhesion layers for bottom electrodes for ferroelectric thin films. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730781]