Studies of copper vacuum arc plasma through an off-plane double-bend filtering duct

A novel off-plane double-bend (OPDB) magnetic filter, designed to remove unwanted macroparticles effectively from the plasma beam of a cathodic vacuum arc, was used in our filtered vacuum arc system to deposit copper thin film as an interconnect material for deep submicron IC applications. A filter with high plasma transmission efficiency is essential for a high deposition rate, which is key to the commercialisation of the technology. Hence, an investigation has been carried out to study the copper arc plasma under varying magnetic field and duct bias. The ion throughput was determined by measuring the ion saturation output current using a copper disc probe. To study further the copper ion motion in the OPDB filter, a modified drift model was applied, which took into account radial electric fields generated by the potential difference between the duct wall and torus centre. Relatively good agreement between the experimental and simulation results were obtained.