Transition from ballistic to thermalized transport of the metal sputtered species in DC magnetron

Adrien Revel (1, 2) , Abderzak El Farsy (1, 2) , Ludovic de Poucques (2) , Jacques Robert (1) , Tiberiu Minea (1)

1 LPGP - Laboratoire de physique des gaz et des plasmas
2 IJL - Institut Jean Lamour

Tunable Diode Laser Induced Fluorescence (TD-LIF) technique has been optimized to accurately measure the titanium (Ti) sputtered Atoms Velocity Distribution Functions (AVDF) in a magnetron discharge operating in Direct Current (DC) mode. The high spatial and spectral resolution achieved unveils some features of the transport of the metal sputtered atoms and their thermalization. The two groups of thermalized and energetic atoms have been very well separated compared to previous works. Hence, the fitting of the energetic atoms group shows dumping from modified Thompson to Gauss distribution when the product pressure-distance from the target increases. In parallel, sputtered metal transport from the target has been simulated using the Monte Carlo collision (MCC) approach. The direct comparison between numerical and experimental results led to an improved cross section for Titanium - Argon momentum transfer, based on the \textit{ab initio} formulae of the interaction potential derived from noble gases interaction. The numerical parametric study of the angular distribution and cut-off energy for the initial distribution of sputtered atoms steered to a precise characterization of the initial conditions, allowed by the accuracy of experimental data. A very good overall agreement is obtained for measured and calculated AVDFs. The confrontation between measured and modeling results emphasized the major role played by the argon ions not only in the sputtering process but also in the neutral metal transport, by the gas rarefaction near the target. The microscopic description provided by the MCC model clearly reveals different transport regimes: ballistic, diffusive, and back-scattering and brings new insights on the thermalization of sputtered species in the intermediate pressure range.

Mots clés: DC magnetron sputtering; tunable diode laser induced fluorescence; MCC model; sputtered atoms velocity distribution function

Domaines: Physique [physics]

Adrien Revel, Abderzak El Farsy, Ludovic de Poucques, Jacques Robert, Tiberiu Minea. Transition from ballistic to thermalized transport of the metal sputtered species in DC magnetron. Plasma Sources Science and Technology, 2021, ⟨10.1088/1361-6595/ac352b⟩. ⟨hal-03473421⟩