MEMS low pressure sensor chip for elevated operating temperatures up to 3000C
Since there is significant demand for measurement of low pressures in fluids with very high temperatures, we are developing a new type of pressure sensors for elevated operating temperatures up to 3000C. To this purpose we use standard planar technologies and wet anisotropic chemical etching of SOI (Silicon-On-Insulator) wafers. This high-temperature sensor is based on the idea that piezoresistors in this case are not insulated mutually and from the substrate by the contact potential of the p-n junction, but by dielectric (silicon dioxide).
Our sensor of absolute low pressures has a square profiled diaphragm with a central boss. Such a diaphragm ensures good lienarity in low pressure sensors. Piezoressitive sensors in Wheatstone bridge are insulated by silicon dioxide both mutually and from the substrate senzora. To process SOI wafers, we utilized maskless technique based on wet chemical etching in aqueous solution of tetramethyl amonium hydroxide..