Improvement of Surface Morphology of Polymer Waveguides for High Sensitivity Optical Biosensor by Chemical Mechanical Polishing

High sensitivity biosensors were investigated in an attempt to improve the surface morphology of polymer waveguides using chemical mechanical polishing technology. The polymer waveguides, based on fluorinated polyethers, were fabricated by a combination of photo-lithography and reactive ion etching, and then their surfaces were polished under a variety of processing conditions. The root means square roughness (RMS) of the polymer waveguide surfaces decreased from 12.8 to 3.7 nm with increasing the polishing time after the dry-etching process. The detection sensitivity of the evanescent field bio-sensor, based on the fabricated polymer waveguide, was examined. A titanium dioxide film with a thickness of 50 nm was deposited on the polymer surface by radio frequency sputtering. A glycerol–water solution was dropped onto the titanium dioxide film deposited on the polymer surface and the interference pattern was measured using an optical system. The measured index change leading to a phase variation of 2π was 4.2 ×10-4.