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

Abstract

The effect of W and WO 3 electrodes on the ferroelectric characteristics of HZO (Zr-doped HfO 2 )-based MFM (metal-ferroelectric-metal) capacitors was investigated. During the deposition of tungsten, the W electrode was formed using only Ar gas, while the WO 3 electrode was formed using a mixture of Ar and O 2 gases. The W-based MFM capacitors exhibited superior remnant polarization (2P r of 107.9 µC/cm 2 at 700 o C) compared to the WO 3 -based capacitors; however, their endurance performance was degraded. In contrast, the WO 3 -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 WO 3 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.