Paper TF-TuP11
Effects of Annealing Gas on Characteristics of High-k Oxide Films (HfO2) Deposited by ALD for MIM Capacitors

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Research on the insulating films in metal-insulator-metal (MIM) capacitors has focused on ways to increase the dielectric constant of insulator to improve the packing density of integrated RF capacitors. High-k oxide (e.g., Ta₂O₅) has been suggested as an alternative material to replace SiO₂ and Si₃N₄. However, reliability problem caused by leakage current may limit the application of Ta₂O₅. Properties of HfO₂ grown on the Si substrate shows a dielectric constant which is comparable to that of Ta₂O₅. Further, the characteristics of HfO₂ more stable than those obtained from Ta₂O₅, suggesting that we may use HfO₂ film as insulator in MIM capacitor. In this work, we report the physical and electrical properties of ALD-deposited HfO₂ film (11-12 nm) annealed at various gases (N₂, O₂, N₂O). HfO₂ films were annealed at 400, 600, 800°C using a rapid thermal processor for 1 min. Top and bottom metal electrodes were Pt and Pd, respectively. The electrical characterization indicates that HfO₂ MIM capacitors fabricated at 800 °C under O₂ ambient show the most desirable electrical properties, such as a high capacitance density of ~16.9 fF/µm², a low leakage current of 2.7×10-4 A/cm² at -5 V, low-voltage coefficients of capacitance, and good-frequency dispersion properties. In addition, better properties were obtained from the samples annealed using N₂O than those of samples treated using N₂. These results indicate that oxygen content has certain role(s) on the electrical properties of ALD-deposited HfO₂ film. These results, as well as further investigation of physical properties of the samples using XPS, will be presented at the conference.