Reactor wall effects in Si–Cl₂–Ar atomic layer etching

Journal Article · Wed Jun 12 00:00:00 EDT 2024 · Journal of Vacuum Science and Technology A

DOI:https://doi.org/10.1116/6.0003651· OSTI ID:2426348

Vella, Joseph R. ^[1]; Elgarhy, Mahmoud I. ^[2]; Hao, Qinzhen ^[3]; Donnelly, Vincent M. ^[3]; Graves, David B. ^[4]

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1. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
2. Univ. of Houston, TX (United States); Al-Azhar University, Cairo (Egypt)
3. Univ. of Houston, TX (United States)
4. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States)

This work complements our previous manuscript [J. Vac. Sci. Technol. A41, 062602 (2023)] where predictions from molecular dynamics (MD) simulations of silicon–chlorine–argon (Si–Cl₂–Ar) atomic layer etching (ALE) are compared to experiments. When etch product distributions for atomic chlorine (Cl) and silicon chlorides were initially compared to optical emission spectroscopy (OES) signals, it appeared that there was a discrepancy between the MD predictions and experimental results at higher ion fluences. Experiments showed a relatively long period of nearly constant Cl-containing etch products released from the ion-bombarded surface (referred to as the “plateau”) but this effect was not observed in MD simulations. In this report, we demonstrate that the “plateau” observed in the OES signals is most likely due to the desorption of Cl-containing etch products from the walls of the reactor and subsequent adsorption on the Si substrate. Experiments varying the gas residence time in the chamber while keeping incoming gas concentrations and pressure constant support this interpretation. We also conducted experiments with an additional Ar-only flow in the chamber to reduce the concentration of Cl-containing species on the chamber walls. For both sets of flow modification experiments, we observe results consistent with the hypothesis that Cl-containing species desorbing from chamber walls are a significant cause of the observed discrepancy between MD predictions and experimental observations. If the measured OES signals are corrected for this “additional” source of Cl-containing species at the surface, the MD predictions and measured OES signals are in excellent agreement. This further supports the predictive capability of MD simulations to accurately capture the relevant physical and chemical processes in plasma-assisted ALE processes. We provide an order of magnitude estimate of the required density of Cl-containing species that would account for the additional etch products observed. Finally, we discuss the implications of this effect on ALE in plasma nanofabrication.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: AC02-09CH11466
• OSTI ID: 2426348
• Journal Information: Journal of Vacuum Science and Technology A, Journal Name: Journal of Vacuum Science and Technology A Journal Issue: 4 Vol. 42; ISSN 0734-2101
• Publisher: American Vacuum Society / AIP
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Atomic-layer etching
Chemical processes
Molecular dynamics
Nanofabrication
Optical emission spectroscopy
Surface and interface chemistry