Bruce R. Scharf

Hybrid integration of light-emitters and detectors with SOI-based micro-opto-electro-mechanical systems (MOEMS)

A multidisciplinary team of end users and suppliers has collaborated to develop a novel yet broadly enabling process for the design, fabrication and assembly of Micro-Opto- Electro-Mechanical Systems (MOEMS). A key goal is to overcome the shortcomings of the polysilicon layer used for fabricating optical components in a conventional surface micromachining process. These shortcomings include the controllability and uniformity of material stress that is a major cause of curvature and deformation in released microstructures. The approach taken by the consortium to overcome this issue is to use the single-crystal-silicon (SCS) device layer of a silicon-on-insulator (SOI) wafer for the primary structural layer. Since optical flatness and mechanical reliability are of utmost importance in the realization of such devices, the use of the silicon device layer is seen as an excellent choice for devices which rely on the optical integrity of the materials used in their construction. A three-layer polysilicon process consisting of two structural layers is integrated on top of the silicon device layer. This add-on process allows for the formation of sliders, hinges, torsional springs, comb drives and other actuating mechanisms for positioning and movement of the optical components. Flip-chip bonding techniques are also being developed for the hybrid integration of edge and surface emitting lasers on the front and back surfaces of the silicon wafer, adding to the functionality and broadly enabling nature of this process. In addition to process development, the MOEMS manufacturing Consortium is extending Micro-Electro-Mechanical Systems (MEMS) modeling and simulation design tools into the optical domain, and using the newly developed infrastructure for fabrication of prototype micro-optical systems in the areas of industrial automation, optical switching for telecommunications and laser printing.