Surface and interface studies of RF sputtered HfO2 thin films with working pressure and gas flow ratio

In this work, hafnium oxide (HfO2) thin films were deposited on p-type silicon substrate by radio frequency magnetron sputtering at various working pressure ranging from 4 x 10(-3) to 1 x 10(-2) mbar and Ar/O-2 flow ratio from 1:4 to 4:1. The morphological and electrical properties of the sputtered films were investigated and a correlation between the surface and electrical properties of the HfO2 films was established with the variation of sputtering parameters. The evolution of monoclinic structure of the hafnium oxide thin films was observed by XRD studies. The surface of the HfO2 films became rough with the increase in grain size at the sputter pressure of 8 x 10(-3) mbar and Ar/O-2 gas flow ratio of 1:4. The formation of HfO2 bond was seen from FTIR spectra. The oxide charge density has a lower value for the sputter pressure of 8 x 10(-3) mbar and Ar/O-2 gas flow ratio of 1:4 due to the evolution of larger grains. The interface charge density was found to be minimum at a sputter pressure of 8 x 10(-3) mbar.