Influence of unipolar pulse time offset between Ti and Zr dual cathodes in closed magnetic field high power impulse magnetron sputtering

Abstract

Titanium/zirconium dual cathodes with a closed magnetic field configuration were used in unipolar high power impulse magnetron sputtering (HiPIMS). Different pulse width (pulse on time) and pulse time offset between the negative voltage pulses of two targets were applied. The target discharge current waveforms and consequent substrate current waveforms were recorded and compared. The results show that both ion fluxes emitted from the Ti and Zr cathodes increase with the argon pressure. However, the ion flux emitted from the Zr cathode increases more substantially at high argon pressure. The closed magnetic field raises the target discharge current and ion flux to the substrate when the pulses of the two targets are simultaneous synchronized, or followed closely. The TiZr film composition is influenced by the HiPIMS discharge behavior of each target material more than by the average power ratio of each target. For low working pressure and short pulse width, simultaneous synchronization of the pulses on the two targets might effectively use the electrons drifting between the dual targets to enhance the generation of ions from both targets. For high working pressure and long target pulse width, setting pulses on two targets following closely is recommended to additionally utilize the runaway ions as pre-ionized media for the follow-up pulse on the adjacent target.