Silicon on sapphire CMOS for optoelectronic microsystems

we report on a hybrid integration approach that represents a paradigm shift from traditional optoelectronic integration and packaging methods. A recent metamorphosis and wider availability of silicon on sapphire CMOS VLSI technology is generating a great deal of excitement in the optoelectronic systems community as it offers simple and elegant solutions to the many system integration and packaging challenges that one faces when employing bulk silicon CMOS technologies. In the bulk silicon CMOS processes that are used for high-speed interface electronics the substrate is absorbing at both 850 nm and 980 nm wavelengths, necessitating complex and expensive integration procedures such as VCSEL substrate removal to enable the implementation of optical vias through the substrate. Working together, the optical transparency of the sapphire substrate, its superb thermal conductivity and the excellent high speed device characteristics of silicon-on-sapphire CMOS circuits make this technology an excellent choice for cost effective optoelectronic Die-AS-Package (DASP) systems and for implementing optical interconnects for high performance computer architectures. What is perhaps even more important, packaging and input/output interface issues can now be addressed at the CMOS wafer fabrication level where input/output structures can be accurately defined, optimized and processed using lithographic techniques, eliminating problematic die post-processing and packaging-related optical alignment issues.