Effects of experimental parameters on NF3 decomposition fraction in an oxygen-based RF plasma environment

Clean procedure is one of the major emitters of perfluorinated compounds (PFCs) in semiconductor manufacturing. Nitrogen trifluoride (NF3) is increasingly the process gas of choice for eliminating PFC emissions. However, its toxic to human and similar global warming potential compared to most other PFCs made NF3 warranted much more investigation. This study demonstrated a radio-frequency plasma system for decomposing NF3. The effects of experimental parameters: input power, O2/NF3 ratio, operational pressure and NF3 feeding concentration on NF3 decomposition fraction (ηNF3) and energy efficiency (ENF3) were examined in detail. The analytical results demonstrated that the NF3 was almost completely decomposed (>99%) at input power = 30 W, [NF3]in = 1.0% and ηNF3 increased with input power. However, adding O2 to the system inhibited NF3 decomposition and decreased ENF3. Moreover, ηNF3 and ENF3 decreased with gradually increasing operational pressure. Notably, increasing the NF3 feeding concentration increased molecule density, reducing ηNF3, but increasing ENF3. Furthermore, the products detected in the NF3/O2/Ar plasma system were NO2, NO, N2O, SiF4, N2 and F2. Potential reaction pathways in the oxygen-based NF3 plasma environment were built-up and elucidated.