The second paper, by Koh et al. and published by SPIE in 2002, studied the plasma etch properties of fluorinecontaining polymers in Ar/C4F8/O2 (400/11/8) etch. A positive NF was added in the equation (6) to fit their data [9].When more than one gas is in the plasma chamber, many species are generated in the gas phase. The total result could vary depending on the gas ratio and other plasma condition. Although the plasma gas in this paper was a mixture of C4F8/O2 at ratio of 11/8, the plasma in the gas phase is still dominated by O2 plasma. The fluorine in the polymer is aslow-etch material in this oxidizing environment. The number of fluorine atoms in the etch equation should be positive