Hafnium oxide thin films deposited by high pressure reactive sputtering in atmosphere formed with different Ar/O2 ratios

The physical and electrical properties of hafnium oxide (HfO2) thin films deposited by high pressure reactive sputtering (HPRS) have been studied as a function of the Ar/O2 ratio in the sputtering gas mixture. Transmission electron microscopy shows that the HfO2 films are polycrystalline, except the films deposited in pure Ar, which are amorphous. According to heavy ion elastic recoil detection analysis, the films deposited without using O2 are stoichiometric, which means that the composition of the HfO2 target is conserved in the deposition films. The use of O2 for reactive sputtering results in slightly oxygen-rich films. Metal-Oxide-Semiconductor (MOS) devices were fabricated to determine the deposited HfO2 dielectric constant and the trap density at the HfO2/Si interface (Dit) using the high–low frequency capacitance method. Poor capacitance–voltage (CV) characteristics and high values of Dit are observed in the polycrystalline HfO2 films. However, a great improvement of the electrical properties was observed in the amorphous HfO2 films, showing dielectric constant values close to 17 and a minimum Dit of 2×1011 eV−1 cm−2.