Breakdown and Langmuir Electrical Characteristics of Glow Discharge Plasma in DC Reactive Dual-Magnetron Sputtering System


In this work, the breakdown and Langmuir characteristics of dc glow discharge plasma employing dual-magnetron assembly were studied. The electrical characteristics of this system are optimized to use it for reactive sputtering applications. The plasma was generated by electric discharge of argon gas at pressures ranging from 0.1 to 0.8 mbar. Also, a mixture of argon and oxygen was used to generate plasma since oxygen is used as the reactive gas. First, the Paschen’s curves for both cases (argon only and argon/oxygen mixture) were plotted as the variation of breakdown voltage with the product of gas pressure (p) and inter-electrode distance (d) (i.e., p.d). The minima of these curves were ranging in 145-208V for different inter-electrode distances. The minima were also determined for the glow discharge of oxygen only to be ranging in 185-320V. In case of argon/oxygen mixture, the minima were ranging in 100-208V. The resistance of the gaseous medium was determined from the I-V characteristics and the argon showed higher resistance when compared to oxygen and argon/oxygen mixture. The plasma parameters, mainly electron and ion temperatures and densities, were determined from the Langmuir probe measurements for argon only and argon/oxygen mixture. Electron and ion temperatures in argon/oxygen mixture were higher than those in only argon. The densities showed contradictive behaviors as the electron density was lower in argon/oxygen mixture, while the ion density was higher in the same mixture.