Effect of Gas Pressure and Flow Rate on the Plasma Power and Deposition Rate in Magnetron Sputtering System

In this contribution, the effect of gas pressure and gas flow rate on the voltage (power) required to strike & maintain an argon plasma and the current – voltage characteristics as well as the deposition rates were investigated in detail using both ferromagnetic Ni as well as Ni81Fe19 targets. A reduction in the voltage required to strike the plasma as the gas pressure and gas flow rate increased in the sputtering chamber and was attributed to the high probability of the ionisation process with increased gas pressure and gas flow rates. The relation between the voltage required to strike the glow discharge and the plasma current, showed a strong linear dependence under all gas pressures and gas flow rates investigated here. The current - voltage relations showed a transition regions which were more clearly noticeable at low gas pressures and gas flow rates. They were attributed to the small amount of gas that existed in the chamber which in turn reduced the ionisation process. For constant gas pressure, lower voltage is required to strike the plasma when the gas flow rate is high and vice versa. The effect of the plasma power on the deposition rate under different gas pressure and flow rate was also considered here. The deposition rate was directly proportional to the plasma power where it increased linearly with increased plasma power. This means that the number of ejected atoms from the target increased linearly by increasing the target power. However, there was a slight reduction in the deposition rate by increasing the gas pressure and flow rates especially at high plasma power. This was attributed to the collisions enhancement among the ejected particlesor/and the gas atoms or due to the reduction in the thermal energy of the sputtered atoms and changing their direction far from the substrate.

Keywords: Current-Voltage characteristics, Glow discharge, Gas flow rate, Gas pressure, Plasma power.