Suppressing oxygen vacancy formation in ZrO₂ to improve electrical properties by employing MoO₂ bottom electrode

The scaling of dynamic random-access memory (DRAM) has driven extensive research not only on insulators and but also on electrodes in capacitor structures. Due to the physical dimensional constraints of these structures, such as their physical thickness, new properties on the electrode are required to improve interface characteristics, including reactivity of the electrode with the insulator and crystallinity coherency, in addition to conventional properties like work function. Traditional electrodes like TiN have suffered to increase leakage currents due to oxygen scavenging effects and a lower work function, which become more severe as DRAM scales down. In this study, we investigate the use of MoO₂ as an alternative electrode material in ZrO₂-based metal-insulator-metal capacitors. MoO₂, with its high work function of 5.5 eV, exhibits excellent crystallinity compatibility with tetragonal-phase ZrO₂ and a low oxidation potential, which collectively lead to enhanced capacitance and significantly reduced leakage current. The MoO₂ electrode suppresses the formation of oxygen vacancies at the interface, as confirmed by x-ray photoelectron spectroscopy and nonlinearity capacitance measurements, resulting in improved device reliability. Our findings suggest that MoO₂ is a promising electrode material for next-generation DRAM capacitors, offering a balance between high capacitance and low leakage current.