Enhanced electrical properties of Hf-aluminate thin films by crystal structure modulation

The Hf-aluminate thin films were deposited by atomic layer deposition using super-cycle and modified super-cycle concepts, and then enhanced electrical properties by crystal structure modulation were investigated. The high temperature tetragonal phase of HfO₂ was stabilized by Al₂O₃ doping and relevant electrical properties were improved through the monoclinic-to-tetragonal transformation. Moreover, the crystallographic direction was changed from the (111) to the (311) orientation by modification of super-cycle for uniform doping of Al₂O₃. The (311)-oriented-tetragonal phase Al₂O₃-doped HfO₂ films had an increased dielectric constant of 42 compared with that of 23 and 33 for monoclinic HfO₂ and (111)-oriented film, respectively.