Characterization of low-k SiCOH film etching in fluorocarbon inductively coupled plasmas

The etching process for the low-k SiCOH films was analyzed using an inductively coupled plasmas system with CF₄/Ar and CHF₃/Ar plasma for nanoscale-integrated devices. The chemical compositions of the etched SiOCH surface, the etch rate, the plasma density, and the ion energy were measured at various bias voltages and source power conditions. The chemical composition of the fluorocarbon layers on the etched SiOCH surface was analyzed with X-ray photoelectron spectroscopy (XPS), and it was revealed that the relative ratio of fluorine and carbon (F/C) on the surface is decreased linearly as the SiOCH etch rate increases. An ion-enhanced etch model was adopted to quantitatively explain low-k SiCOH film etching phenomena. A positive linear relationship was observed between the experimental etching rates and the voltage^1/2 ion flux by the ion-enhanced etch model, and the energy dependence parameter shows the condition of the etch target surface with the generated fluorocarbon polymer.