Plasma abatement of perfluorocompounds in inductively coupled plasma reactors

Perfluorinated compounds (PFCs), gases which have large global warming pote ntials, are widely used in plasma processing for etching and chamber cleani ng. Due to underutilization of the feedstock gases or by-product generation , the effluents from plasma tools using these gases typically have large mo le fractions of PFCs. The use of plasma burn-boxes located downstream of th e plasma chamber has been proposed as a method for abating PFC emissions wi th the goals of reducing the cost of PFC abatement and avoiding the NOx for mation usually found with thermal treatment methods. Results from the two-d imensional Hybrid Plasma Equipment Model have been used to investigate the scaling of plasma abatement of PFCs using plasma burn-boxes. An inductively coupled plasma (ICP) etching chamber is modeled to determine the utilizati on of the feedstock gases and the generation of by-products. The effluent f rom the etching chamber is then passed through a plasma burn-box excited by a second ICP source. O-2, H-2, and H2O are examined as additive gases in t he burn-box. We find that C2F6 (or CF4) consumption in the etching reactor increases with increasing ICP power deposition at constant C2F6 (or CF4) mo le fraction, and decreasing C2F6 (or CF4) mole fraction or total gas flow r ate at constant power. The efficiency of removal of C2F6 (eV/molecule), how ever, is strongly dependent only on the C2F6 mole fraction and total gas fl ow rate. All PFCs in the effluent can generally be abated in the burn-box a t high power deposition with a sufficiently large flow of additive gases. I n general CF4 generation occurs during abatement of C2F6 using O-2 as an ad ditive. CF4 is not, however, substantially produced when using H-2 or H2O a s additives. The efficiency of PFC abatement decreases with increasing powe r and decreasing additive mole fraction. (C) 2000 American Vacuum Society. [S0734-2101(00)02401-5].