Dependence of photoresist surface modifications during plasma-based pattern transfer on choice of feedgas composition: Comparison of C4F8- and CF4-based discharges

The authors report a study of the impact of surface chemical factors on etch rates along with surface and line edge roughness introduction for prototypical photoresist (PR) materials and structures during plasma-based pattern transfer employing fluorocarbon (FC) discharges. For selected photoresist materials and model polymers (193nm PR, 248nm, PR, and polymethyladamantyl methacrylate), the influence of bulk polymer properties on plasma durability was clarified by comparing etch rates, surface roughness introduction, and profile evolution of nanostructures. They studied the effects of both fluorocarbon fragment deposition and polymer surface fluorination by gas phase fluorine atoms on plasma etching resistance and surface roughness evolution of the organic materials by comparing discharges fed with C4F8∕Ar or CF4∕Ar∕H2 gas mixtures. The spatial frequency distribution of surface roughness was obtained using fast Fourier transformation of atomic force microscopy data. A graphitic layer was formed for Ar con...