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 /spl mu/m 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 /spl mu/m into this structure show that it is suitable for optical interconnect applications.