Interfacial and electrical characterization of HfO2 gate dielectric film with a blocking layer of Al2O3

HfO₂ gate dielectric films with a blocking layer of Al₂O₃ inserted between HfO₂/Si were treated with rapid thermal annealing process at 700degC. The interfacial structure and electrical properties are reported. X-ray photoelectron spectroscopy indicated that the interfacial layer of SiO_x transformed into SiO₂ after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. High-resolution transmission electron microscopy showed that the interfacial layer was composed of SiO₂ for the annealed film with a blocking layer. The electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to -4.5times10¹¹/cm² in comparison with the same thickness of HfO₂ films without the blocking layer. Al₂O₃ layer could effectively prevent the diffusion of Si into HfO₂ film and improve the interfacial and electrical performance of HfO₂ film.