Properties of secondary ions in ion beam sputtering of Ga2O3.

The energy distributions of secondary ions for the ion beam sputtering of a Ga 2 O 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 α , polar emission angle β , scattering angle γ), 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. [ABSTRACT FROM AUTHOR]