Study of La-Incorporated HfO2 MIM Structure Fabricated Using PLD System for Analog/Mixed Signal Applications

Metal-insulator-metal (MIM) capacitors with Al/HfO₂/La₂O₃/Al structure were fabricated using pulse laser deposition for the first time and were further investigated for their electrical and morphological properties. The MIM capacitors for future applications in analog/mixed signal circuits need further improvement in their electrical characteristics. We have fabricated MIM capacitors having low leakage current density of ~9.6 × 10^-9 A/cm² at -1 V and high-capacitance density ~20.8 fF/μm² at 3.5 V for 100-Hz frequency. The frequency dispersion effect of these MIM capacitors is observed to be quite small. We have also obtained an improved voltage coefficient of capacitance of ~101 ppm/V² at 1 MHz along with improved dielectric constant which is one of the most important parameters for next generation MIM capacitors. The physical thickness of HfO₂ /La₂O₃ dielectric film stack is found to be 13 nm in cross-section TEM. This value of physical thickness is consistent with the low EOT ~1.66-nm estimated using C-V curve. Morphological studies of having nanostructured film morphology with low roughness are consistent with the electrical characteristics of MIM capacitors. Further improvement in electrical properties like lower leakage current density, etc., has been obtained in post metallic annealed MIM capacitors. We have observed Schottky emission as the dominant current conduction mechanism for these MIM capacitors.