OPTIMIZING ATOMIC LAYER ETCHING SELECTIVITY USING PLASMAENHANCED SURFACE PASSIVATION AND FLUOROCARBON PRECURSOR ENGINEERING

Atomic Layer Etching (ALE) has emerged as a critical technology in advanced semiconductor manufacturing,enabling atomic-scale precision in material removal for sub-5 nm node fabrication. Achieving high etch selectivitybetween dissimilar materials remains a significant challenge, especially in complex device architectures involvingheterogeneous stacks. This study investigates a hybrid approach to optimize ALE selectivity by integratingplasma-enhanced surface passivation with fluorocarbon precursor engineering. The methodology leverages theformation of selective passivation layers under controlled plasma conditions to protect target materials, whiletailoring fluorocarbon species to enhance the reactivity of sacrificial layers. A combination of in situ diagnostics—including real-time spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and optical emissionspectroscopy (OES)—was employed to characterize the surface chemistry and layer dynamics throughout ALEcycles. The study focused on SiO₂/Si₃N₄ and TiN/HfO₂ interfaces, demonstrating significant improvements in etchselectivity (>50:1) without compromising anisotropy or throughput. The findings reveal that precise control overplasma parameters such as ion energy, radical density, and substrate temperature enhances the self-limiting natureof the etching step, while engineered fluorocarbon precursors modify surface energetics to suppress unwantedmaterial removal. Furthermore, reactive molecular dynamics simulations corroborated experimental results bymapping interaction potentials and reaction pathways of passivated surfaces exposed to tailored fluorocarbonspecies. These insights open new avenues for ALE process tunability, especially in high-aspect-ratio and 3DNAND structures. This integrated strategy offers a scalable and CMOS-compatible pathway to meet the stringentselectivity demands of next-generation devices