Evaluation of fluorinated polyimide etching processes for optical waveguide fabrication

Fluorinated polyimides have attracted much attention as potential materials fur optical waveguide fabrication due to their high thermal stability, hum idity resistance, as well as low optical loss in the wavelength region of o ptical communications. For the Fabrication of optical waveguide structures, reactive ion etching (RIE) has been widely used. According to our study, t he highest etch rate obtained with vertical profile for RIE of fluorinated polyimides with O-2 plasma was 300 nm/min. Inductively coupled plasma (ICP) etching of Ultradel(R) 9020D fluorinated polyimide has been conducted to o btain waveguide channels with higher etch rate and more vertical profile th an is possible with RIE. The etch rate and the etch profile have been inves tigated as a function of ICP power, r.f. chuck power, O-2 flow rate, and ch amber pressure. Etch rates of 1700 nm/min to 2200 nm/min with vertical prof ile and smooth sidewall were obtained by ICP etching at an ICP power of 500 W, r.f. chuck power of 150 W to 350 W. chamber pressure of 5 mTorr and O-2 flow rate of 40 seem. Under these conditions there was no appreciable chan ge in the etch rate with chamber pressure in the range 5-20 mTorr. (C) 1999 Published by Elsevier Science S.A. All rights reserved.