Reaction surface analysis of plasma etching of SiN, SiO2, and poly-Si films using low-global warming potential CF3CHCF2 gas

Controlling material selectivity in plasma etching is a critical challenge for next-generation semiconductor devices, particularly for achieving high etching rates while obtaining passivation-controlled sidewall shape profiles. In this study, the key reactive species generated in 1,1,3,3,3-pentafluoropropene (C₃HF₅) plasma are investigated, including etching ions (hydrofluorocarbons C_2-3HF_1,3-5⁺ and perfluorocarbons C_2-3F_3-5⁺) and passivating precursors. Their roles in the selective etching of silicon nitride (SiN), silicon dioxide (SiO₂), and polysilicon (poly-Si) films are revealed by analyzing material-specific surface interactions governing the etching kinetics using integrated in situ quadrupole mass spectrometry and ex situ X-ray photoelectron spectroscopy. For SiO₂ surfaces, the high etching rate of 415 nm/min is driven by efficient fluorine flux from C_2-3F_3-5⁺ and C_2-3HF_1,3-5⁺ species. While, SiN surfaces exhibit a moderate etching rate of 290 nm/min, sustained by hydrogen supplied from C_2-3HF_1,3-5⁺ ions. Conversely, poly-Si surfaces show significantly reduced etching rates (<130 nm/min), attributed to carbonaceous passivation. By controlling the partial pressure of C₃HF₅, high selectivity ratios of SiO₂/poly-Si and SiN/poly-Si are critically achieved for high-aspect ratio etching. These insights establish a universal plasma parameter optimization strategy for advancing selective etching processes for high-aspect ratio features in semiconductor devices.