Calculations of thermalization during the sputter deposition process

Abstract

During the sputter deposition process both the sputtered atoms and reflected neutral atoms contribute to the overall energy flux to the growing film. The sputtered atoms have typically 5–20 eV as they leave the target. The reflected neutrals may have considerably more energy though the number reflected towards the substrate is highly system dependent. These energetic atoms collide with the sputtering gas and transfer some of their energy to the gas atoms as they travel to the substrate. Recent theoretical predictions of Robinson have shown the scattering cross-sections for these energetic atoms is considerably less than the standard thermal scattering cross-sections. We calculate the main effect of these energy dependent, as opposed to thermal, scattering cross-sections is a twofold decrease in the effectiveness of the sputtering gas in thermalizing the sputtered atoms and an even greater effect on the more energetic reflected neutrals. In this paper the energy distribution of the energetic atoms as they are progressively thermalized is presented; in our previous calculation we considered only an average. These results for the energy distributions are related to some phenomena associated with the sputter deposition of metallic films.