Fabrication of Spin-Coated Optical Waveguides for Optically Interconnected LSI and Influence of Fabrication Process on Underlying Metal–Oxide–Semiconductor Capacitors

Abstract

A microscopic optical waveguide fabrication technique on silicon substrates at low temperatures using a fluorinated polyimide (FPI) is developed for application in an optically interconnected LSI. Propagation loss decreases to about 1.0 dB/cm in the miniaturized FPI waveguide with a core size of 1.5×10 µm2 made on a thermal oxide film and to about 4.8 dB/cm in a waveguide with a core size of 1×10 µm2 made on spin-on-glass. Furthermore, the FPI waveguides are also fabricated on metal–oxide–semiconductor (MOS) capacitors, and the influence of the waveguide fabrication including a plasma etching process on the underlying MOS capacitors is evaluated by examining the time-dependent dielectric breakdown characteristics. It is observed that plasma damage in the dry etching process may not be so large, but the damage at the spin-coating step for spin-on-glass for clad layer formation on a MOS capacitor is relatively large in the FPI waveguide fabrication process.