Monte Carlo Simulation of Fast Neutrals impinging on Substrate

In the current semiconductor device manufacturing processes, the main energetic particles considered to be incident on the substrate are electrons and ions. The existence and effects of fast neutrals, which are produced in plasma sheaths due to ion-neutral collisions[1], have not been considered so far. Recently, the incident angular distribution of fast neutrals has become measurable[2], rekindling the need to understand their impact on plasma processes. In this study, the single/dual-frequency sheath model for noble gases[3] has been extended to arbitrary gas chemistries by introducing ion-neutral collision cross sections generated by DNT+DM[4]. The extended sheath model enables analysis of incident energy and angular distributions (EADs) of fast neutrals, and ion reaction rates in a sheath. As an example, the sheath model has been applied to an rf capacitively coupled plasma in Ar at 0.1 Torr in a GEC reference cell[5]. The flux of fast Ar is 6.39 times larger than that of Ar⁺, indicating the consideration of the EADs of fast Ar is more crucial than that of Ar⁺. Other simulation results of an Ar/H₂ plasma for a deposition process will also be presented in the conference.

[1]T. Ito and M. A. Cappelli, J. Appl. Phys. 106, 023305 (2009). [2]K. Ichikawa et al., Appl. Phys. Express 14, 126001 (2021). [3]K. Denpoh et al., Jpn. J. Appl. Phys. 43, 5533 (2004). [4]K. Denpoh et al., J. Vac. Sci. Technol. A 42, 053002 (2024). [5]K. Denpoh et al., Jpn. J. Appl. Phys. 64, 04SP65 (2025).