Electrostatically bonded pressure transducers for corrosive fluids

Abstract

Differential transducers for corrosive or electrically conductive fluids have a first tube for guiding such fluids toward one side of a semiconductor diaphragm containing embedded strain gages, and a second tube for guiding such fluids toward an opposite side of that semiconductor diaphragm. These tubes are made of an electrically insulating material temporarily convertible to an electrical conductor for electrostatic bonding. The semiconductor diaphragm is provided in a semiconductor wafer extending beyond the perimeter of at least the first tube. The strain gages are provided with embedded electrical leads extending beyond the above mentioned perimeter for attachment of electrical contact wires outside the first tube, while providing these leads inlaid in the semiconductor wafer at least in a region to be covered by the first tube. The wafer including the semiconductor diaphragm is integrally sandwiched between layers of material providing electrical conduction for electrostatic bonding at the tubes and electrical insulation and isolation of the diaphragm and strain gages from corrosive or electrically conductive fluids guided toward the diaphragm by the tubes. Each of the tubes is temporarily converted to an electrical conductor, and these first and second tubes are electrostatically bonded to the above mentioned layers with the aid of the above mentioned electrical conduction, to form the tubes, layers and wafer with semiconductor diaphragm, strain gages and electrical leads into an integrated bonded structure.