Atomic Layer Etching Characteristics of SiO ₂ Using Reactive Species Controlled from Low-GWP C ₄ H ₂ F ₆ Isomers

This study investigates the atomic layer etching (ALE) characteristics of silicon-based compounds using C 4 H 2 F 6 isomer gases, which exhibit a low global warming potential (GWP < 20) and offer carbon reduction potential. C 4 H 2 F 6 isomers exhibit limited physisorption on substrates at room temperature, making them unsuitable for conventional ALE processes. To overcome this limitation, a custom-designed reactive species generation module was developed to enhance surface deposition during ALE. The dissociation behavior and reactive species generation of the C 4 H 2 F 6 isomers under plasma discharge were characterized using optical emission spectroscopy and quadrupole mass spectrometry. The ALE characteristics under varying deposition conditions were analyzed using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. As the deposition time of the reactive species increased, the etch per cycle (EPC) of SiO 2 increased. XPS analysis revealed that the atomic concentrations of carbon (C) and fluorine (F) increased proportionally with the deposition time. Additionally, the C 4 H 2 F 6 -iso isomer exhibited slightly higher EPC values compared to the C 4 H 2 F 6 -E isomer. This difference is attributed to the variations in the composition and concentration of the reactive species, particularly CF x and C x H y F z species, generated during plasma discharge, which influence the etching and polymerization dynamics on the surface.