Properties of secondary ions in ion beam sputtering of Ga2O3

The energy distributions of secondary ions for the ion beam sputtering of a Ga 2O 3 target using O 2 + and Ar + ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters include sputtering geometry (ion incidence angle alpha, polar emission angle beta, scattering angle gamma), the energy of incident ions E ion, and the background pressure of O 2. The main secondary ion species are identified to be Ga +, O +, O 2 +, and, when argon is used as a process gas, Ar +. The changes in the sputtering geometry and the primary ion energy have the most impact on the energy distributions of secondary Ga + and O + ions, giving control over the high-energy tail, which is attributed to anisotropy effects in sputtering. The formation of O 2 + ions is attributed to collisions with background gas molecules, as their energy distributions are not influenced by the sputtering geometry or the primary ion energy. The increase of the O 2 pressure leads to a minor decrease of the energy of Ga + ions due to collisions with the background gas particles. The use of primary Ar + ions with O 2 background pressure does not show any specific effect on energy distributions of Ga +, O +, and O 2 + ions except for the case without additional O 2 background. In the latter case, much fewer O + and O 2 + ions are produced indicative of oxygen depletion of the surface due to preferential sputtering of oxygen. At all considered O 2 pressures, the energy distributions of Ar + ions have a high-energy peak, attributed to direct scattering events. The trends in experimental data show qualitative agreement to simulations using the Monte Carlo code SDTrimSP.

Automated summary

The energy distributions of secondary ions for ion beam sputtering of a Ga2O3 target using O2+ and Ar+ ions were measured and found to be influenced significantly by the sputtering geometry and the energy of incident ions for Ga+ and O+ ions. The formation of O2+ ions was attributed to collisions with background gas molecules. Increasing O2 pressure led to a minor decrease in the energy of Ga+ ions due to collisions with background gas particles. The use of primary Ar+ ions with O2 background pressure did not show any major effect on the energy distributions of Ga+, O+ and O2+ ions.