The time dependence of the ion composition in pulse-modulated dual-frequency capacitively coupled plasma with Ar/C4F8/O2 was measured using a quadrupole mass spectrometer with an electrostatic energy analyzer. After turning on the pulse, Ar+ ions were preferentially generated, and then, the composition of CxFy + ions, such as C2F4 + and C3F5 + ions, increased. This phenomenon was discussed on the basis of the time variation of electron temperature and the resultant change in the ratio of the C4F8 ionization rate to that of Ar atoms.

In this study, a novel phenomenological model is developed to predict the etching yields of SiO2 and SiNx substrates by fluorocarbon (FC) and hydrofluorocarbon (HFC) ions. The CF layer thickness and reactive layer chemistry are described, which significantly affect the etching yields. The study focuses on the dependence of the atomic component of the ion and the incident ion energy of the ion on the etching yield. Some assumptions enable the calculation of ion etching yields in a short turn-around-time. The proposed model can predict the etching yields of other larger species at the higher incident ion energy. The obtained simulation results are in good agreement with the experimental data. The optimal etching ions for high aspect ratio etching are comprehensively investigated using the proposed model, providing a better understanding of the differences in the underlying material and the atomic component of the ion.

In the dry etching process using fluorocarbon (FC) gas, deposited amorphous-CFx (a-CFx) films in patterns, such as holes and trenches, strongly affect the etching performance. The influence of the FC gas molecular structures and their atomic compositions on the formation of a-CFx films at different positions in the holes were investigated. It was found that the deposition region and thickness of the a-CFx film strongly depend on the molecular structures of the FC gas, such as double bonds, benzene rings, and the atomic ratio of fluorine to carbon.