Enhanced Retention Characteristics of Pb(Zr, Ti)O3 Capacitors by Ozone Treatment

Effects of ozone treatment and charged defects on retention characteristics of Ir/IrO2/Pb(Zr, Ti)O3 (PZT)/Pt/IrO2/Ir capacitors were systematically investigated. For these purposes, PZT thin films were exposed to ozone environment to promote enhanced surface oxidation. After baking the Ir/IrO2/PZT/Pt/IrO2/Ir capacitors at 125°C for 500 h, degradation of Qnv (non-volatile charge) value of the ozone-treated capacitors was approximately 17.6%, that is less than one fifth of that of the untreated capacitors. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) studies showed that the amount of oxygen-vacancies near the PZT surface was dramatically decreased by the ozone treatment. The Schottky barrier height of the ozone-treated capacitors increased when compared to that of the untreated capacitors (the Schottky barrier height of the untreated and the ozone-treated capacitor was 0.29 eV and 0.43 eV, respectively). Therefore, one can conclude that the retention characteristics seem to be closely associated with oxygen related defects near the ferroelectric/electrode interface and the control of the interface properties of PZT thin film is a key technology to pursue reliable function characteristics of ferroelectric random access memory (FRAM) devices.