Four-terminal-gauge quasi-circular and square diaphragm silicon pressure sensors

Five pressure sensors with a four-terminal gauge using shear stress have been developed. In order to obtain high fracture strength of the sensors, a quasi-circular diaphragm, in place of a square one, has been made by an aqueous solution of potassium hydroxide and isopropyl alcohol. Since a four-terminal gauge is small, four four-terminal gauges with different distances from the centre are made on a diaphragm so that an optimum gauge for various pressure ranges, i.e., various thickness of the diaphragm, can be chosen. This sensor makes a custom pressure sensor possible. For measuring very low pressures, a square pressure sensor consisting of a cross rib with the four-terminal gauge, thin membranes and a centre boss (EI-type cross-section) has been developed. This sensor can be used as an acceleration sensor by etching off the membranes.