Realistic Etch Yield of Fluorocarbon Ions in SiO2 Etch Process

The energy distribution and flux of ions striking an rf-biased electrode were measured by using an rf floating ion energy analyzer. Energies of CF1 +, which was the dominant species, were distributed over a voltage range of about half the peak-to-peak bias voltage. Energetic ions with neutral radicals, forming the reactive fluorocarbon polymer layer on a SiO2 film, affected etching characteristics such as rate and selectivity. To investigate the chemical activity of the reactive layer, we estimated the etch yield of SiO2 from the given energy distribution of the ions and the etch rate of SiO2. We found that the energy dependence of the etch yield should be controlled by precisely regulating the flux and composition of neutral radicals under a given ion flux, in order to obtain a high etch rate under the actual SiO2 etching conditions.