Investigation of sheath electron temperature in RF capacitively-coupled plasmas using PIC simulations.*

Radio-frequency capacitive-coupled (RFCC) discharges have increasing applications in semiconductor manufacturing, plasma propulsion, and nanomaterial fabrication, but many aspects of their operation remain poorly understood. Popular low pressure (< .1 Torr) models for RFCC plasmas assume homogeneous electron temperature (ET) [1], even in inhomogeneous models [2], and a recent model of intermediate-pressure (.2 – 6 Torr) RFCC plasmas assumes strictly lower sheath-edge ET than bulk ET [3]. Experimental evidence has shown, however, that at high pressure (200 Torr) ET peaks at the sheath edge [4]. Using the 1D particle-in-cell (PIC) code EDIPIC, and the recently developed 2D PIC code EDIPIC-2D, sheath electron temperature in low and intermediate-high pressure regimes is characterized and compared with these models and previous experimental results.

 

[1] P. Chabert, “Single-frequency capacitively coupled plasmas,” in Physics of Radio Frequency Plasmas (CUP, Cambridge, 2011).

[2] M. A. Lieberman and A. J. Lichtenberg, “Capacitive Discharges,” in Principles of Plasma Discharges and Materials Processing (Wiley, New York, 1994).

[3] E. Kawamura, et al., J. Vac. Sci. Technol. A 38, 023003 (2020).

[4] S. Park, W. Choe, and H. Kim, Scientific Reports 8, 10217 (2018).