Effects of capacitively-coupled radio-frequency discharge on operation voltage in magnetron sputtering

Ionized magnetron sputtering (MS) has gained more interest due to the flexible process control and better surface properties. A new apparatus utilizing capacitively-coupled radio-frequency (RF) discharge is described here. The sample holder is connected to the RF power and pulse bias systems. The influence of the continuous or pulsed RF discharge on the operation voltage of MS system is investigated. The operation voltage is observed to decrease when the RF discharge is ignited. It is attributed to the enhanced plasma density in front of the sputter target. The variation in the operation voltage depends on the MS current. At a low MS current, the operation voltage decreases with increasing RF discharge power. In contrast, the operation voltage increases at higher RF discharge power together with a higher MS current. A larger RF pulse width does not increase the operation voltage although the average RF power increases. The TiN films fabricated using this apparatus possess better corrosion resistance and wear resistance despite a large friction coefficient. It is believed to be due to the synergistic effects of the higher plasma density and self-biasing at higher RF power. Our results demonstrate that this special magnetron sputtering process that couples the sample holder to the RF discharge and negative bias is an effective approach to achieve better surface properties.