Low-k SiOCH Film Etching Process and Its Diagnostics Employing Ar/C5F10O/N2 Plasma

We proposed an environmental harmonic etching gas of C 5 F 10 O (CF 3 CF 2 CF 2 OCFCF 2 ), and demonstrated the etching of low- k SiOCH films employing a dual-frequency capacitively coupled etching system. Dissociative ionization cross sections for the electron impact ionizations of C 5 F 10 O and c-C 4 F 8 gases have been measured by quadrupole mass spectroscopy (QMS). The dissociative ionization cross section of CF 3 + from C 5 F 10 O gas was much higher than those of other ionic species, and 10 times higher than that of CF 3 + from C 4 F 8 gas. CF 3 + is effective for increasing the etching rate of SiO 2 . As a result, the etching rate of SiOCH films using Ar/C 5 F 10 O/N 2 plasma was about 1000 nm/min, which is much higher than that using Ar/C 4 F 8 /N 2 plasma. The behaviours of fluorocarbon radicals in Ar/C 5 F 10 O/N 2 plasma, which were measured by infrared diode laser absorption spectroscopy, were similar to those in Ar/C 4 F 8 /N 2 plasma. The densities of CF and CF 3 radicals were markedly decreased with increasing N 2 flow rate. Etching rate was controlled by N 2 flow rate. A vertical profile of SiOCH with a high etching rate and less microloading was realized using Ar/C 5 F 10 O/N 2 plasma chemistry.