The spatial and temporal variation of potentials in the HiPIMS discharge

We describe measurements of the plasma parameters in a high power impulse magnetron sputtering (HiPIMS) discharge. A Langmuir probe is used to determine the plasma parameters, such as the electron temperature $T_{\mathrm{eff}}$, the electron density $n_{\mathrm{e}}$, the floating potential $V_{\mathrm{fl}}$ and the plasma potential $V_{\mathrm{pl}}$, as well as the electron energy distribution function (EEDF). The spatial and temporal variation of the plasma parameters and electron energy distribution function are recorded in the pressure range $3 - 20$ mTorr. The electron density peaks at $5 \times 10^{18}$ m$^{-3}$ for $40 - 80$ mm distance from the target surface for all pressures investigated. The electron temperature reaches its peak value of $1.5 - 3$ V roughly $80~\mu$s after pulse initiation, in the pressure range $5 - 20$ mTorr. The plasma potential and the floating potential peak at the end of the pulse. We will in particular describe the spatial variation of the plasma and floating potentials at various times during the discharge.