Abstract

The development of optically interconnected VLSI and wafer-scale systems has as a prerequisite the existence of a light modulator technology compatible with logic circuit technology that will enable the unconstrained placement of a large number of logic-driven light sources on a die or wafer. Integrated lasers, multiple-quantum-well electroabsorption modulators, and organic electrooptic materials exhibit high speed but are sufficiently mature to permit system prototyping, especially in silicon. Ferroelectric liquid crystals (FLCs) possess low switching energies and driving voltages in the surface-stabilized cell configuration¹ and are, therefore, well matched to the output characteristics of silicon CMOS logic gates. Rapid development of faster materials is under way with switching times of 3 μs at 15 V/μm available now. We present a procedure that incorporates fabrication of most components of a reflective surface-stabilized FLC light modulator cell into an unmodified bulk CMOS process flow. The reflective electrode and 1-1.5-μm thick spacer can be obtained by specifying features in the mask description of the die. Light sources can thus be placed in the same manner as transistors. The only postprocessing steps that need be applied to the silicon die are the application of an aligning layer to ensure proper smectic layer orientation and assembly of the cells with a common transparent cover electrode.

© 1988 Optical Society of America