Hyper Power Impulse Magnetron glow discharge
High Power Impulse Magnetron Sputtering (HiPIMS) becames nowadays a very versatile way to taylor the film properties and better control the growth of the thin fims. However, looking back to the initial idea, HiPIMS has been proposed by the end of the last century to overcome the arc transition, but allowing the glow operation of the discharge beyond the regular abnormal regime, i.e., achieving high currents with high operating voltages. The transition to arc is, in this case, simply avoided by the pulse duration control, typi-cally 100 µs. The average power is compara-ble with the direct current (dc) operation, choosing the duty cycle in the same ratio as the current density ratio in HiPIMS over dc mode, namely within a factor of 100 to 1000, leading to average peak current densities up to 10 A/cm2 in respect to the target surface
In this communication, we report a new glow discharge mode obtained with a regular mag-netron cathode, in pulsed mode, but with cur-rent density much higher than the upper HiP-IMS limit. Moreover, the pulse duration is very long (~1 ms) corresponding to a quasi-steady state. It is clearly different from both, HiPIMS and arc discharge, since the opera-tion voltage stays well between the two typi-cal ranges, which are beyond 500 V for HiP-IMS and below 100 V for arcs. The power density approaches 0.5 MW per pulse for a 2 inch target, so we call it Hyper Power Im-pulse Magnetron (HyPIM) glow discharge.
The first diagnostics of HyPIM mode are pre-sented and discussed, as well as the behav-iour of the discharge in HiPIMS and the phe-nomena leading to arc transition. A typical image of the glow discharge in HyPIM regime is depicted in Fig. 1, taken with a high speed camera.
Three target materials have been successfully tested: carbon (C), molybdenum (Mo) and tungsten (W) in helium atmosphere 10-30 Pa. Two key parameters have been indentified as necessary to be fulfilled for reaching HyPIM mode: (i) the operation voltage must be ex-ternally limited and (ii) the pre-ionization of the gas is mandatory before the pulse appli-cation.
In addition, we will introduce this glow re-gime on the well-known current-voltage characteristic of the discharges and will dis-cuss on optimal (E x B) design compared with other high current configurations. We will also emphasize some possible applica-tions of this novel discharge mode.
Tibériu Minéa, Erwan Morel, Yoann Rozier
Presented at Plasma Tech 2021