Fabrication of fluorinated polyimide waveguides on copper-polyimide multilayer substrates for opto-electronic multichip modules

We have developed new opto-electronic substrates, which are key components for constructing opto-electronic multichip modules. These substrates consist of optical waveguides (for OEIC chip-to-chip optical interconnection) on copper-polyimide multilayers for high-speed electrical transmission. Low-loss (0.4 dB/cm) fluorinated polyimide ridge waveguides with nearly vertical and smooth sidewalls (<0.1 p m) on copper-polyimide multilayer substrates are achieved using spincoating, photolithographic patterning, and highly selective dry etching. The low propagation loss is retained even after heat-treatment at the soldering temperature of 300°C. The uniformity of the waveguide film thickness is about ±2% and the uniformity of the etched depth in the ridge waveguides (including the fiber-guiding groove) is about ±2% over the whole substrate (9×9 cm). This new substrate achieves self-aligned fiber-to-waveguide coupling with a low coupling loss deviation (≃0.1 dB)