SiO$_{2}$ Film Etching Process Using Environment-Friendly New Gas C$_{5}$F$_{7}$H

With the continuous miniaturization of semiconductor memory devices, a much precise etching process for a high aspect ratio contact hole in SiO$_{2}$ film is indispensable. Furthermore, deterioration of the SiO$_{2}$ selectivity over a fragile, thin ArF photoresist would cause the sidewall roughness and poor pattern-width definition. In this study, we utilized a newly designed C$_{5}$F$_{7}$H gas. We compared the etch performances between the new gas and conventional C$_{5}$F$_{8 }$. Ar and O$_{2}$ were introduced with the each fluorocarbon gas to controll the etching rate. A dual frequency (60 MHz / 2 MHz) capacitively coupled plasma was employed. The SiO$_{2}$ etching rate and selectivity to ArF photoresist were investigated as a function of O$_{2}$ flow rate. The maximum selectivity of only 3.7 and the SiO$_{2}$ etching rate of 416 nm/min were obtained at O$_{2}$ flow rate of 20 sccm for the C$_{5}$F$_{8}$/O$_{2}$/Ar plasma. For the newly developed C$_{5}$F$_{7}$H/O$_{2}$/Ar plasma, the maximum selectivity of 13.5 with the etching rate of 356 nm/min was achieved at 25-sccm O$_{2}$ flow rate. From these results, it was confirmed that almost four times higher selectivity than that of the conventional C$_{5}$F$_{8}$ gas was obtained by using the new C$_{5}$F$_{7}$H gas.