The optimized oxygen inductively coupled plasma etching parameters are systematically studied to fabricate Poly (methyl-methacrylate-glycidly-methacrylate) inverse ridge waveguide with smooth vertical features. The etch rate, surface roughness and vertical profile are characterized by atomic force microscopy and scanning electron microscopy. The optimized etching parameters are found to be 400-W antenna-RF power, 30-W radio frequency (RF) bias power, 1-Pa-chamber pressure, and 40-sccm be O2-flow rate. Spincoating butyl acetate diluted polymer solution onto the channel waveguide is proved to be an effective method which can decrease the surface roughness. According the results, the RMS rouqhness of the film decreases 80%. Optical propagation loss can be reduced from 2.6 to 1.5 dB/cm for the above reason.