| abstract |
The pressure transducer includes a semiconductor cantilever beam, a diaphragm, a spacer, and a back plate. The diaphragm, spacer, and back plate are bonded together at their peripheries to form a cup. The ends of the beam are bonded, respectively, to the supported periphery of the diaphragm and to an intermediate deflecting portion thereof, whereby pressure forces within the cup are transmitted by the diaphragm to the beam. Piezoresistive elements are diffused into the surface of the beam to produce an electric signal in accordance with the strain produced in the beam as the result of the pressure forces. In one embodiment, the beam is a flat plate. In another embodiment, the beam includes a portion at the mounting end that is massive relative to the stress sensitive portion of the beam. The juncture of the massive mounting portion and the stress sensitive portion is an abrupt step, whereby a precise fulcrum for the stress sensitive beam portion is provided. In another embodiment, a relatively massive beam portion also is provided at the movable end of the beam remote from the mounting end. Other embodiments include a wire or a spring inserted between the movable end of the beam and the deflecting portion of the diaphragm. The transducer materials and bonds are chosen to minimize hysteresis, which procedure includes making the internal viscosity of the diaphragm at least closely approach that of the beam. |