Surface etching properties of a thermally curable polymer based on fluorinated polyether for polymer waveguide biosensor applications

In this study, to achieve a low polymer surface roughness, we studied a thermally curable polymer based on highly fluorinated polyether to examine the effects of antenna power, bias power, and gas flow rate in oxygen plasma. The polymer surface roughness was unaffected by the O ₂ flow rate and the antenna power, but increased with increasing bias power. These results indicate that the polymer based on fluorinated polyether was more affected by ion bombardment than by chemical etching by O ₂. The surface roughness was also affected by the variation in antenna power due to the influence of plasma-induced ion bombardment after a long etching time. Therefore, the surface roughness of the polymer based on fluorinated polyether was more dependent on the bias power and the etching time than on the antenna power and the gas flow rate for same etching time. As a result, a low surface roughness was acquired at an etching condition of low bias power and short etching time. However, because of the shallow hole shape of the polymer surface, the etching condition of 1000-W antenna power and 300-W bias power was determined to be the most suitable for a long etching time. A polymer waveguide with a single mode at a 1064-nm wavelength was fabricated under this optimum etching condition.