Sidewall chemistry of nano-contact patterns in C4F8 + CH2F2 + O2 + Ar inductively coupled plasmas

Highlights: • The characteristics of the sidewall etching residue were investigated. • A thinner polymer was formed on the sidewall of the nanopatterns than on the surface. • The chemical composition of the sidewall residue varied with the profile depth. -- Abstract: In this study, silicon dioxide contact holes were etched with C₄F₈ + CH₂F₂ + O₂ + Ar gas plasmas, and the characteristics of the etching residue thereby generated inside the nanopatterns were investigated. The chemical composition of the etching residue formed on the sidewalls of the nano-contact patterns in the gas chemistry was investigated at various oxygen partial pressures by performing in situ Ar sputtering and X-ray photoelectron microscopy at different take-off angles. To investigate the effect of the plasma-active species (polymerizing radicals and charged species) on the formation of the etching residue, plasma diagnostics were conducted via optical emission spectroscopy and Langmuir probe measurements. It was found that as the oxygen content of the plasma increased, the thickness of the fluorocarbon (FC) polymer layer formed on the sidewalls of the nanopatterns decreased with a reduction in the FC polymer deposition rate of the plasma. In addition, at higher aspect ratios, the FC polymer layer showed a lower fluorine content.