Contact-Hole Etching with NH 3 -Added C 5 F 8 Pulse-Modulated Plasma

For plasma etching, an alternative perfluorocarbon (PFC) gas is necessary in order to minimize the effect on global warming. Etching contact holes of sub-0.1-µm size in SiO 2 is studied using an etching gas with a small greenhouse effect, cyclic (c-) C 5 F 8 containing various other gases (O 2 , H 2 and NH 3 ). Adding NH 3 to pulse-modulated plasma is quite effective for improving the etching characteristics compared with adding O 2 or H 2 . Adding NH 3 improves both the hole profile and etching selectivity. The influence of the added NH 3 gas was analyzed by optical emission spectroscopy (OES), and the correlation between the flow rate of NH 3 , the OES results, and the SiO 2 etching rate was studied.