Interfacial thermal stability and band alignment of Al_2O_3/HfO_2/Al_2O_3/Si gate stacks grown by atomic layer deposition

摘要

Based on X-ray photoelectron spectroscopy (XPS) and oxygen energy loss spectra, influences of vacuum annealing temperature on the interfacial thermal stability and band alignment of Al_2O_3/HfO_2/Al_2O_3/Si gate stacks deposited by atomic layer deposition has been investigated. It has been revealed that annealing the multilayered Al_2O_3/HfO_2/Al_2O_3 structure from 500 to 600 °C leads to the formation of the composited Hf-Al-O alloy thin film. Meanwhile, phase separation of Hf-Al-O into HfO_2 and Al_2O_3 for samples annealed at 700 °C and silicate formation for sample annealed at 900 °C has been observed. The band profiles, obtained via oxygen energy loss spectroscopy, provided us some insight, which is both convenient and at the same time important, into the way to identify high-fc dielectric materials, and we also found that Al_2O_3/HfO_2/Al_2O_3/Si gate stacks annealing at suitable temperature range of 500-700 °C could be a promising candidate for high-fc gate dielectrics.