In situ analyses on negative ions in the indium-gallium-zinc oxide sputtering process

The origin of negative ions in the dc magnetron sputtering process using a ceramic indium-gallium-zinc oxide target has been investigated by in situ analyses. The observed negative ions are mainly O^- with energies corresponding to the target voltage, which originates from the target and barely from the reactive gas (O₂). Dissociation of ZnO^-, GaO^-, ZnO₂^-, and GaO₂^- radicals also contributes to the total negative ion flux. Furthermore, we find that some sputtering parameters, such as the type of sputtering gas (Ar or Kr), sputtering power, total gas pressure, and magnetic field strength at the target surface, can be used to control the energy distribution of the O^- ion flux.