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초록

Silicon oxynitride (SiON) thin films are widely used as mask materials for amorphous carbon layer (ACL) patterning, where high etch selectivity and stable profile control are required. In this study, the etching characteristics of SiON mask layers were systematically investigated using C3F6/C4F8/He plasmas in a 2 MHz bias inductively coupled plasma system, with direct comparison to conventional CF4-based chemistry under ultra-low-pressure conditions. Despite its significantly lower global warming potential (GWP), the C3F6-based plasma exhibited SiON etch rates comparable to those of CF4 while consistently providing enhanced selectivity to photoresist over a wide range of gas-mixing conditions. Representative cross-sectional SEM images confirmed that anisotropic and well-preserved SiON profiles were maintained, indicating that the improved selectivity was achieved without compromising profile integrity. Plasma diagnostics and surface analyses suggest that the enhanced selectivity originates from controlled fluorocarbon surface reactions without excessive polymer accumulation. In addition, exhaust-line Fourier transform infrared spectroscopy analysis combined with mass-manufactured total CO2 equivalent (MMTCE) evaluation revealed reduced greenhouse gas emission characteristics for the C3F6-based process compared to CF4. These results indicate that C3F6 is a viable low-GWP alternative to CF4 for SiON mask etching, offering improved selectivity, stable profile control, and reduced environmental impact in ACL-related fabrication processes.

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