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High‐aspect‐ratio (HAR) etch of SiO2 films was attempted using a low‐frequency (2 MHz) bias power in an inductively coupled plasma (ICP) system using heptafluoroisopropyl pentafluoroethyl ketone (C6F12O) gas, which has a lower global warming potential (GWP). Etching characteristics of the oxide film according to changes such as the CF4/C6F12O mixing ratio, source power (13.56 MHz), and bias power were derived. To understand the etching characteristics and mechanism, optical emission spectroscopy (OES), double Langmuir probe (DLP) measurement, and X‐ray photoelectron spectroscopy (XPS) analysis were performed. We observed the vertically etched profile of the 100 nm etched line pattern with a scanning electron microscope (SEM) and at first suggested that the HAR oxide etching process is feasible using the ICP system.

In this work, we discuss the effects of component ratios on plasma characteristics, chemistry of active species, and silicon etching kinetics in CF4 + O2, CHF3 + O2, and C4F8 + O2 gas mixtures. It was shown that the addition of O2 changes electrons- and ions-related plasma parameters rapidly suppresses densities of CFx radicals and influences F atoms kinetics through their formation rate and/or loss frequency. The dominant Si etching mechanism in all three cases is the chemical interaction with F atoms featured by the nonconstant reaction probability. The latter reflects both the remaining amount of fluorocarbon polymer and oxidation of silicon surface.

In this study, we investigated the effect of Ar/He mixing ratio in the tetrafluoromethane/perfluorocyclobutane/Ar/He gas mixture on plasma parameters, SiO2 etching kinetics, and etching selectivity with respect to the amorphous carbon layer (ACL) mask in the inductively coupled plasma system with the low frequency (2 MHz) bias source. It was found that the type of dominant carrier gas does influence the output process characteristics through changes in both ion flux and CFx/F ratio determining the plasma polymerizing ability. In particular, He‐rich plasmas exhibited better performance with respect to the faceting of ACL mask and SiO2/ACL etching selectivity.

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