Sputter deposition of titanium monoxide and dioxide thin films with controlled properties using optical emission spectroscopy

TiOx thin films with various oxygen atomic ratios (x) were deposited on Si(100) wafers without intentional heating by radio-frequency magnetron sputtering of a Ti target using Ar discharge plasma, mixed with increasing O2 flow supply. Optical emission spectroscopy was employed to monitor the intensity of Ti emission lines via a flow-supply feedback loop. By circumventing the processing hysteresis, this set-up allowed the process windows along the metallic-poisoned curve to be found for the controlled deposition of TiOx thin films, particularly titanium monoxide (x = 1.0) and oxides with the values of x in the vicinity of 2.0. The physical properties of these films (deposition rate, electrical resistivity, composition, phase distribution, etc.) were investigated and correlated well with each other. At the as-deposited states, the TiO1.0 film is polycrystalline, but the films with x ranging from 1.54 to 2.2 are amorphous. Finally, the crystallization behavior of these amorphous films after annealing was examined and the impact of the initial oxygen content in the pristine films on the crystallization tendency and final crystal structure was elucidated.