Media-Compatible Electrically Isolated Pressure Sensor For High Temperature Applications

A method for manufacturing a Micro-Electro-Mechanical System (MEMS) pressure sensor, the method comprising:

• forming a gauge wafer comprising a diaphragm region and a pedestal region, wherein a first surface of the diaphragm region is configured to be accessed by a pressurized medium that exerts a pressure resulting in a deflection of the diaphragm region;
• forming an electrical insulation layer disposed on a second surface of the diaphragm region opposite to the first surface;
• forming a plurality of sensing elements patterned on the electrical insulation layer disposed on the second surface in the diaphragm region, wherein a thermal expansion coefficient of the material of the sensing elements substantially matches with a thermal expansion coefficient of the material of the gauge wafer;
• forming a cap wafer with a central recess in an inner surface;
• forming a plurality of through-wafer embedded vias made of an electrically conductive material in the cap wafer;
• creating a sealed cavity by coupling the inner recessed surface of the cap wafer to the gauge wafer, such that the sensing elements are enclosed in the recess, and electrical connections from the sensing elements come out to an outer surface of the cap wafer opposite to the inner recessed surface through the electrically conductive through-wafer embedded vias;
• forming a spacer wafer with a central aperture;
• and
• attaching the spacer wafer to the pedestal region of the gauge wafer with the central aperture aligned to the diaphragm region.