<title>Micromachined silicon structures for single-mode passive alignment</title>

Penetration into the fiber-in-the-loop (FITL) and fiber-to-the-curb (FTTC) markets requires a drastic cost reduction in optoelectronic packaging. To achieve this goal, passive alignment techniques were developed using micromachined silicon waferboard technology which showed great potential for the tight tolerances (plus or minus 0.5 micrometers) required to passively align optoelectronic devices to single mode fibers. In this technology, micromachined alignment pedestals and standoffs precisely locate the x, y, and z positions of optoelectronic devices, which have matching alignment notches, to the optical fiber confined by a v-groove. The tight tolerances are possible using precision photolithography and well controlled reactive ion etching (RIE). In this paper, we report our process development results of forming micromachined silicon alignment pedestals using RIE. We demonstrate RIE etch depth control for the 6 micrometer z-standoffs with a 0.13 micrometer standard deviation and etch profile control for the x and y alignment pedestals to within 0.25 micrometers for each edge, which were obtained across a 3-inch wafer and from run to run. Such high precision control on RIE etch profile and uniformity is extremely important in developing manufacturable processes.