Helium and hydrogen trapping in tungsten deposition layers formed by helium plasma sputtering

Tungsten deposition layers were formed by helium plasma sputtering utilizing a capacitively coupled RF plasma. For comparison, hydrogen plasma was also used for the formation of the deposition layer. It was found that non-negligible amount of helium and hydrogen were trapped in the tungsten deposition layer formed helium plasma sputtering. It is considered that the hydrogen emitted from the plasma chamber wall by helium plasma discharge was trapped in the layer. Atomic ratio of helium to tungsten (He/W) in the layer was estimated to be 0.08. This value is not quite small compared with that of hydrogen in the tungsten deposition layer formed by hydrogen plasma sputtering. The release behavior of helium from the layer formed by helium plasma sputtering was similar to that of hydrogen from the layer formed by hydrogen plasma sputtering.