Research Review of the Plasma with Spoke Characteristic for High Power Impulse Magnetron Sputtering

High Power Impulse magnetron sputtering (HiPIMS) is the latest generation of magnetron sputtering technology, and highly ionized pulsed plasma is the core feature of HiPIMS technology. This paper reviews the latest advances in plasma simulation, measurement of HiPIMS and its effect on film growth based on its spoke discharge characteristic. Compared with the conventional magnetron sputtering technology, the target particles are highly ionized and the plasma resistance is significantly reduced in HiPIMS. The plasma can form dense plasma structures that rotate at a speed of kilometer pen second on the surface of the target. With the characteristics of localization and self-organization, they can significantly affect the transport behavior of deposited particles and provide a new control dimension for film deposition. Spokes generally present diffuse shape and triangle shape in HiPIMS. Through the detailed introduction of the change law of spokes and the progress of the formation mechanism, it is clear that the sputtering yield of the target materials also affects spokes' morphology. On the other hand, combined with the pulse modulation, spokes can control the transport characteristics of the film deposition flux, thereby affecting the microstructure of the deposited film, surface roughness and other surface integrity parameters. Modulated Pulsed Power magnetron sputtering (MPPMS) and Deep Oscillation magnetron sputtering (DOMS) with the microsecond to millisecond cross-scale multi-level pulse adjustment capability, could be used to control the film growth in a larger spatial dimension due to the tailored spoke characteristics brought about by the cross-time scale characteristic of pulse control.