Molecular structure effects on dry etching behavior of Si-containing resists in oxygen plasma

The authors have studied the influence of Si–O bonding in the polymer structure of Si-containing resists on O2 plasma etch behavior. Three polymers were synthesized with the same Si wt % (12.1%) and varying number of Si–O bonds (0, 1, or 2). The etch resistance during the plasma process was measured by monitoring the film thickness removed using real-time in situ ellipsometry. After plasma exposure, surface chemical changes and roughness were characterized by x-ray photoelectron spectroscopy and atomic force microscopy, respectively. For O2 plasma exposure without substrate bias, all polymers showed the formation of a ∼1 nm SiO2 layer at the surface that acted as a barrier to further oxygen etching. Adding Si–O bonds to the polymer structure at constant wt % Si greatly reduced the etch rate and Si loss during oxygen plasma etching relative to the case of no such bonds. Polymers with one Si–O bond in the polymer structure showed identical etch behavior to polymers with the same wt % Si and two Si–O bonds. ...