Measurement-Based Estimation of Emission Factors for CF4, C4F6, and C4F8 in Semiconductor Etching Under Varying Plasma Conditions

In the semiconductor industry, fluorinated gases with high global warming potential (GWP) are recognized as significant sources of greenhouse gas emissions. This study presents a measurement-based analysis of a 300 mm wafer etching process using CF4, C4F6, and C4F8 gases. The use rate of gas (Ui), unreacted fraction (1-Ui), and by-product generation rate (Bi) were evaluated under varying plasma intensity conditions. The results show that the unreacted fraction (1-Ui) decreased with increasing plasma intensity for all process gases, indicating enhanced gas dissociation efficiency. In contrast, the by-product generation rate (Bi) exhibited non-linear behavior due to the complex interplay of dissociation and recombination reactions within the plasma. Furthermore, the measured Ui and Bi values showed significant deviations from the default emission factors provided in the 2006 IPCC Guidelines and the 2019 Refinement. Variability analysis based on the coefficient of variation (CV) was conducted using measurements obtained under different plasma conditions (n = 3). The results indicate that Ui exhibited relatively stable behavior with low variability (CV < 0.3), whereas Bi showed higher variability depending on the type of by-product gas, reflecting stronger sensitivity to process conditions. These findings highlight that IPCC default emission factors may not adequately reflect actual process conditions and underscore the importance of incorporating measurement-based, condition-dependent variability into emission estimation.