Effect of Sputtering Gas Ions on Thin Film Properties

In thin films that are prepared by sputtering, internal stress is generated during film formation. Internal stress is widely known to induce substantial changes in the properties of thin films, including their mechanical and optical properties and electromagnetic characteristics. The internal stress of sputtered films, which is generated by changes in their sputtering powers and gas pressures and substrate biases, is affected by ion bombardment during thin-film deposition. In our recent research, we studied methods of measuring the ion energy in the plasma and sheath regions using a multigrid electrostatic ion analyzer and a Langmuir probe. The obtained data suggested that the effect of ion bombardment can be quantitatively evaluated. In the present study, sputtered thin films were deposited using different sputtering gases and varying substrate biases. We attempted to control the internal stress of the deposited thin films by evaluating the ionic bombardment during film deposition as ion-bombardment parameter P-i, which was affected by the sputtering gas ions. The results demonstrate that the internal stress of the thin films decreased with increasing the ion. bombardment parameter P-i. The compressive stress was increased by the peening effect of the sputtering gas ions. Therefore, evaluating the internal stress of thin films using the ion-bombardment parameter P-i is feasible.