Silicon-based fabrication process for production of optical waveguides

The fabrication of silicon waveguides for use as optical interconnects in silicon optoelectronic integrated circuits for wavelengths beyond 1.1 μm is described. The process does not require silicon-on-insulator technology, and only uses VLSI processing techniques. Long, thin mesas are etched from a silicon substrate and masked along their sides with silicon nitride. The ridges are then isotropically dry etched to undercut the walls. The remaining silicon is thermally oxidised to leave a single-crystal silicon core encased in silicon dioxide. The cross-sectional area of the silicon cores is determined by the anisotropic silicon etch and the oxidation time. Waveguides with dimensions six by four microns surrounded by a micron-thick oxide layer have been fabricated. Results of launching light of wavelength 1.5 μm into this structure show that it is suitable for optical interconnect applications