Atomic layer deposition of HfO2 using HfCp(NMe2)3 and O2 plasma

HfO2 thin films were prepared by plasma-enhanced atomic layer deposition using a cyclopentadienyl-alkylamido precursor [HfCp(NMe2)3, HyALD™] and an O2 plasma over a temperature range of 150–400 °C at a growth per cycle around 1.1 Å/cycle. The high purity of the films was demonstrated by x-ray photoelectron spectroscopy and elastic recoil detection analyses which revealed that by increasing the deposition temperature from 200 to 400 °C, the atomic concentrations of residual carbon and hydrogen reduced from 1.0 to <0.5 at. % and 3.4 to 0.8 at. %, respectively. Moreover, Rutherford backscattering spectroscopy studies showed an improvement in stoichiometry of HfO2 thin films with the increase in deposition temperature, resulting in Hf/O ratio close to ∼0.5 at 400 °C. Furthermore, grazing incidence x-ray diffraction measurements detected a transition from amorphous at the deposition temperature of 300 °C to fully polycrystalline films at 400 °C, consisting of a mixture of monoclinic, tetragonal, and cubic phases. Finally, the surface morphology and conformality of HfO2 thin films studied by atomic force microscopy and transmission electron microscopy are also reported.