Integration of high-k dielectric thin films and hetero-structures in MIS capacitors

High-density capacitors with capacitance density >5nF/mm² and leakage currents in low micro-amp/cm² have been integrated using high permittivity (k) dielectrics in MIS structures for mixed signal application. The high-k dielectrics studied were Hafnium Oxide (HfOx), Tantalum Oxide (TaOx) and hetero-structures of HfOx/TaOx. These films were deposited by ALCVD and the thermal budget of the entire process flow was restricted to <450°C, including the final passivation treatment. For the different dielectrics and hetero-structures, dependencies of the electrical properties on variations such as dielectric thickness, presence of barrier layers, and applied bias were studied. Capacitance densities above 5nF/mm² were easily achieved while restricting the leakage currents to acceptable μ-amp/cm² at applied voltages of 5.5 Volts. Also, a preliminary investigation of the reliability of these dielectrics exhibited promising results.