Oxygen reservoir effect of Tungsten trioxide electrode on endurance performance of ferroelectric capacitors for FeRAM applications

The effect of W and WO₃ electrodes on the ferroelectric characteristics of HZO (Zr-doped HfO₂)-based MFM (metal-ferroelectric-metal) capacitors was investigated. During the deposition of tungsten, the W electrode was formed using only Ar gas, while the WO₃ electrode was formed using a mixture of Ar and O₂ gases. The W-based MFM capacitors exhibited superior remnant polarization (2P_r of 107.9 µC/cm² at 700 ^oC) compared to the WO₃-based capacitors; however, their endurance performance was degraded. In contrast, the WO₃-based capacitors showed endurance performance enhanced by three orders of magnitude due to the oxygen-rich reservoir effect. The oxygen introduced during the deposition of WO₃ prevented the oxygen scavenging effect of tungsten. Consequently, excessive generation of oxygen vacancies in the HZO layer was suppressed, resulting in improved endurance performance. These results were quantitatively confirmed through TEM, XPS, and XRD analyses.