Application of porous silicon to bulk silicon micromachining

A fully C-MOS compatible process for bulk silicon micromachining using porous silicon technology and front-side lithography is developed. The process is based on the use of porous silicon as a sacrificial layer for the fabrication of deep cavities into monocrystalline silicon, so as to avoid back side lithography. Cavities as deep as several hundreds of micrometers are produced with very smooth surface and sidewalls. The process is used to produce : a) suspended monocrystalline silicon membranes, b) free standing polysilicon membranes in the form of bridges or cantilevers with lateral dimensions from a few mu ms to several hundreds of mu ms. Important applications to silicon integrated devices as sensors, actuators, detectors etc., are foreseen.