What question did this study set out to answer?

The research aims to explore the effect of fluorocarbon-assisted plasma-enhanced atomic layer etching on the etching quality and repeatability of SiO2.

February 26, 2026

Fluorocarbon (C4F8) assisted plasma-enhanced atomic layer etching (PEALE) of SiO2 with high repeatability of cycles in industrial ICP reactor. I. experiment

Key Points

The research aims to explore the effect of fluorocarbon-assisted plasma-enhanced atomic layer etching on the etching quality and repeatability of SiO2.
Utilized a classical PEALE approach involving CxFy deposition and Ar+ ion activation.
Introduced an additional step for cleaning with oxygen atoms to enhance results.
Monitored PEALE dynamics in an industrial 200 mm reactor using laser ellipsometry and plasma diagnostics.
Analyzed surface states using ex situ x-ray photoelectron spectroscopy.
The activated Ar+ ions (50 eV) caused minimal defects in SiO2 while promoting effective reactions at the interface.
Increased ion energy (∼130 eV) led to defect generation in the SiO2 upper layer.
The optimized CxFy thickness and Ar+ energy contributed to a low-damage PEALE process with high repeatability.

Abstract

Deep understanding of plasma-surface interaction processes largely determines the progress of modern plasma technologies in microelectronics. Creating reliable ultrasmall nanometer-level devices requires precise low-damage processes. This paper investigates the implementation of fluorocarbon (C4F8) assisted plasma-enhanced atomic layer etching (PEALE) of SiO2 in an industrial 200 mm reactor. The “classical” approach to PEALE of SiO2 is used: (i) deposition of a reactive CxFy nm layer and (ii) activation of reactions at the “CxFy–SiO2” interface by Ar+ ions. We added step (iii), removal of reaction products and reactor cleaning with oxygen atoms. The PEALE dynamics of SiO2 is observed using an in situ laser ellipsometer and a set of plasma diagnostics. The surface state during all steps of the PEALE cycle is analyzed using ex situ x-ray photoelectron spectroscopy. It is shown that the defects in the upper SiO2 layer can be generated by using the energetic (∼130 eV) ions for activation and cleaning. Activation of the ∼1–1.5 nm CxFy layer by low-energy (∼50 eV) Ar+ ions mainly promotes reactions at the “CxFy–SiO2” interface without introducing defects into the underlying SiO2 layers, while the surface is essentially fluorinated. The low-damage PEALE process can be implemented by synchronously optimizing the CxFy thickness and Ar+ energy to release ion energy into the CxFy layer. The use of an additional step using O atoms from the Ar/O2 plasma to remove reaction products and fluorocarbon residues allows us to carefully reproduce both the SiO2 state and the reactor surface state, providing well-controlled PEALE of SiO2 with high repeatability.

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