Thin film deposition using a plasma source with a hot refractory anode vacuum arc

Abstract

Vacuum arc generated plasma was used to deposit metallic Al, Zn, and Sn coatings on glass substrates. An arc mode with a refractory anode and an expendable cathode (the “hot refractory anode vacuum arc”), overcomes macroparticle (MP) contamination experienced in other arc modes. I = 100–225 A arcs were sustained between a water-cooled coating source cathode and an anode, which was heated by the arc, separated from each other by a 10-mm gap, for times up to 150 s. The distance from the arc axis to the substrate (L) was 80–165 mm. Film thickness was measured with a profilometer. It was found that the deposition rate increased with time to a peak, and then decreased to a steady-state value. The peak occurred earlier when using short anode (9 mm long), e.g., with the Al cathode, L = 110 mm, and I = 200 A, the peak was at t p = 15 s after arc ignition while with the long anode t p = 45 s. t p decreased with I, from 45 s with I = 100 A, to 10 s with I = 225 A with the short anode. The peak is believed to appear due to initial condensation of cathode material (including MPs) on the cold anode, and its subsequent evaporation as the anode heated. In the later HRAVA steady state, a balance between condensation and evaporation on the anode is established. The deposition rate peak was significant with low melting temperature Al and Zn cathodes, which produce many MPs, and negligible with Cu and Ti cathodes.