Thermal stability of Al- and Zr-doped HfO₂ thin films grown by direct current magnetron sputtering

Ultrathin HfO2 dielectric films doped with Al and Zr were grown on p -type Si(100) substrates by dc magnetron sputtering, and their microstructural and electrical properties were examined. Compositions and chemical states of the dielectric films were analyzed by Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy. The HfO2 films doped with Zr were crystallized even from the as-deposited state, however, the crystallization temperature of the HfO2 film doped with 16% Al2O3 was delayed up to 900 °C. As the annealing temperature increases, high-resolution transmission electron microscopy analyses of all doped HfO2 films showed an increase of the interfacial layer thickness due to the diffusion of small partial pressure of oxygen in annealing ambient. Our results also showed that the addition of Al2O3 to 14% is not useful for blocking the oxygen diffusion through the (HfO2) 0.86 (Al2 O3) 0.14 film. From the capacitance-voltage measurements, the dielectric constants of the Al- and Zr-doped HfO2 thin films were measured to be 18.7 and 7.6, respectively.