Molecular dynamics simulations at the plasma-surface interface

The development of advanced etching processes requires a fundamental understanding of the reaction mechanisms involved in plasma-material interaction. Combined with in-situ diagnostics of plasma and surfaces, molecular dynamics (MD) simulations can provide information on the processes involved at the atomic scale and help to understand the phenomena governing etching. Since 2011, MD simulations developed in the team have proved to be a powerful tool/support to assist the development of new processes. These atomistic simulations are used to study elementary surface reactions [1], explain physico-chemical mechanisms that cannot be probed experimentally, or study how the nature, flux and energy of plasma species (ions, reactive radicals) affect the structural and chemical modification of substrates [2].

Molecular dynamics simulations of plasma-surface interaction: from the plasma reactor to the atomic scale.

In recent years, our work on chlorine plasmas/silicon interactions has demonstrated the theoretical feasibility of a PE-ALE (Plasma Enhanced Atomic Layer Etching) etching concept using ultra-fast modulation of gas injection [3]. Simulations carried out on hydrogen plasmas/graphene interaction provided energy/flow ranges in which H2 plasmas could be used to clean, pattern or exfoliate graphene [4]. More recently, work on the SmartEtch process has led to a better understanding of the self-limiting dynamics and modification mechanisms induced by the implantation of light ions (He+/Hx+) in SiN or SiO2 materials [5].

MD simulation of the SmartEtch implantation step: bombardment of Si3N4 with Hx+ ions and H radicals.

In parallel, fluid/hybrid simulations (0D or 2D) of the plasma are also being developed to study the transport and kinetics of species (ionic and radical) in the gas phase [6]. To be validated, numerical predictions are then tested in real etching experiments carried out in our industrial reactors, in which the plasma and exposed surface are characterized by in situ diagnostics.

References:

[1] Elementary processes of H2 plasma-graphene interaction: A combined MD and DFT study, E Despiau-Pujo, A Davydova, G Cunge et al, J. Appl. Phys. 113, 114302 (2013), 10.1063/1.4794375
[2] Key plasma parameters for nanometric precision etching of Si films in chlorine discharges, P Brichon, E Despiau-Pujo, O Mourey, O Joubert, J. Appl. Phys. 118, 053303 (2015), 10.1063/1.4928294
[3] Plasma Etching Process, O Joubert, G Cunge, E Despiau-Pujo, E Pargon, N Posseme, US Patent 20150228495, Aug 13 (2015)
[4] Hydrogen plasmas processing of graphene surfaces, E Despiau-Pujo, A Davydova, G Cunge, DB Graves, Plasma Chem. Plasma Process. 36, 213-229 (2016), 10.1007/s11090-015-9683-0
[5] Helium plasma modification of Si and Si3N4 thin films for advanced etch processes, V Martirosyan, E Despiau-Pujo, J Dubois, G Cunge, O Joubert, J. Vac. Sci. Technol. A 36, 041301 (2018), 10.1116/1.5025152
[6] Pulsed Cl2/Ar inductively coupled plasmas processing: 0D model vs. experiments, E Despiau-Pujo, M Brihoum, P Bodart, M Darnon, G Cunge, J. Phys. D: Appl. Phys. 47, 455201 (2014), 10.1088/0022-3727/47/45/455201