Improved Dielectric Constant and Leakage Current of ZrO₂-Based Metal-Insulator-Metal Capacitors by Si Doping

As the feature size of dynamic random access memories (DRAM) continues to scale down, the shrunk storage capacitors have met essential challenges, namely, the insufficient capacitances and the excessive leakage currents. In this article, the electrical properties of silicon-doped zirconia (ZrO2) films, with the goal of improving their properties for use as capacitor dielectric for DRAM, were investigated. The results indicated that the introduction of an appropriate amount of Si can increase the portion of the tetragonal crystal phase in ZrO2 dielectric, thereby leading to an increase in the dielectric constant by 26.8%. Even higher Si content leads to the degradation of the crystal structure. Additionally, Si doping likely deepens the depth of defect energy levels in the dielectric, which may suppress the leakage current of the metal-insulator-metal (MIM) capacitors. Compared with the un-doped samples, the leakage current was reduced by 60.2% at the operating voltage of 0.8 V. The equivalent oxide thickness (EOT) was reduced by 17.5% at the standard leakage current density ( \lt 1 \times 10^{-{7}} A/cm2 at 0.8 V). It demonstrated that the Si doping strategy can effectively enhance the capacitance of capacitors and suppress leakage current, thereby addressing the critical issues associated with ZrO2-based MIM capacitors.