ExB plasmas generated by e-beams and non-thermal electrons for materials processing applications

There is growing interest in low-temperature, magnetized plasmas generated by electron beams and non-thermal electrons for atomic-scale materials processing, with applications in microelectronics and quantum systems [1,2]. These plasmas—characterized by densities of ~10⁹–10¹⁰ cm⁻³ and electron temperatures of ~0.1–0.5 eV—are typically formed by injecting energetic electrons (10²–10⁴ eV) into a low-pressure (1–10s mtorr) background gas along an applied magnetic field (~10–100 G). The magnetic field confines the plasma and spatially separates regions of energetic core electrons from colder peripheral populations. These partially ionized, partially magnetized plasmas are prone to instabilities such as beam-plasma and gradient-drift modes, which can impact electron transport and ion heating [3]. For soft processing applications, these effects are often undesirable, as they introduce plasma non-uniformities and enhance ion-induced substrate damage. In this talk, we examine how the electron energy distribution function (EEDF) of the injected electrons influences plasma formation and instability dynamics. Emphasis will be on mitigation of these instabilities and control of plasma kinetics using active boundaries [4,5], as well as on the importance of geometric effects on electron cross-field transport.

References:

[1] D. R. Boris, S. C. Hernández, E. H. Lock, Tz. B. Petrova1, G. M. Petrov and R. F. Fernsler, ECS J. Solid State Sci. Technol. 4 N5033 (2015)

[2] C. Pederson, R. Giridharagopal, F. Zhao, S. T. Dunham, Y. Raitses, D. S. Ginger, K-M. Fu, Phys. Rev. Mater. 8, 036201 (2024)

[3] M. Tyushev, M. Papahn Zadeh, V. Sharma, M. Sengupta, Y. Raitses, J.-P. Boeuf, and A. Smolyakov, Phys. Plasmas 30, 033506 (2023)

[4] E. Rodriguez, V. Skoutnev, Y. Raitses, A. Powis, I. Kaganovich, and A. Smolyakov, Phys. Plasmas 26, 053503 (2019)

[5] N. S. Chopra, I. Romadanov, Y. Raitses, Appl. Phys. Lett. 33, 125003 (2024)