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.