Silicon nitride etch characteristics in SF6/O2 and C3F6O/O2 plasmas and evaluation of their global warming effects

Effects of process parameters on the etch rate and generation of etch by-product molecules during Si3N4 layer etching in SF6/O2 and C3F6O/O2 plasmas were investigated in a dual-frequency capacitively coupled plasma etcher in order to evaluate the etch characteristics and global warming effects of emitted gases. The effects of the working pressure and gas flow ratio on the Si3N4 etch rate were initially examined for each gas mixture. The Si3N4 etch rates was compared for the SF6/O2 and C3F6O/O2 etch gas mixtures under the same process conditions. The by-product gases generated during etching were analyzed and their concentrations were quantized by Fourier transform infrared spectroscopy. The global warming effects caused by the by-product gases emitted using the SF6 and C3F6O gas mixtures were evaluated by comparing the million metric tons of carbon equivalent (MMTCE) values obtained from the emitted amounts of the by-product gases during the etching of a 1 μm-thick Si3N4 layer. The results showed that the C3F6O/O2 chemistry was superior to the SF6/O2 chemistry in lowering the global warming effects. C3F6O gas could be used as an alternative to replace SF6 gas for future etching processes of flat panel display materials.