United Technologies Corporation

Arthur G Foyt

James L Swindal

Robert H Bullis

Walter J Wiegand, Jr

Daniel H Grantham

Robert N Sacks

Richard E Swarts

Sears W Merritt

Robert A Wagner

Mario T Lopiccolo

Paul L Provenzano

A silicon capacitive pressure sensor is disclosed having a silicon diaphragm and a silicon substrate arranged in parallel and separated by a glass dielectric spacer. The glass is deposited onto a surface of the substrate using an ion milling machine. The sensor further includes a transition piece attached to a second layer of glass insulator disposed between the silicon diaphragm and the transition piece. The transition piece has a throughbore formed therein for applying a fluid to a surface of the silicon diaphragm, the fluid having a pressure desired to be measured by the sensor. The glass disposed between the diaphragm and the transition piece is deposited onto the transition piece using the ion milling process.

Silicon capacitive pressure sensor having a glass dielectric deposited

Manufacturing hinged diaphragms for semiconductor sensors (e.g., accelerometers, pressure transducers, etc.), from a SIMOX wafer (W, FIG. 3 A), in which the internal, insulating, silicon dioxide (SiO.sub.2) layer (3) is used as an etch stop in removing silicon from the underside of the wafer by etching with an appropriately selective etch, producing the reduced thickness, peripheral 'hinge' areas (9; FIG. 3 A to FIG. 3 B), with the exposed part of the silicon dioxide layer being removed in a subsequent etching step (FIG. 3 B to FIG. 3C) using a different, selective etch. This produces a single layer, single-crystal, silicon 'hinge' (9'; FIG. 3C) of uniform, continuous material, enhancing the linearity of diaphragm movement during use and the sensor's sensitivity and accuracy. (See FIG. 4 for methodological steps.) If the top, silicon region of the SIMOX wafer is insufficiently thick for the desired diaphragm thickness, additional layer(s) of epitaxial silicon are grown on the upper side of the silicon crystal until the desired thickness is reached; the same being true for increasing the thickness of the silicon substrate. If having reduced thickness areas for the 'hinge' on both sides of the diaphragm are desired, a SIMOX wafer having an intermediate, silicon dioxide layer on both the 'bottom' and the 'top' of the wafer is used, with each layer serving as an etch stop on its respective side, with the then exposed portions of the silicon dioxide layers thereafter being removed, leaving flanking, alternating, silicon 'hinge' bridges (90a/90b; FIG. 5A-C).

Methodology for manufacturing hinged diaphragms for semiconductor sensors

A micromachined three-plate capacitive accelerometer incorporates hinges attached to top and bottom surfaces of the proof mass that are symmetric about X and Y axes and also about diagonal axes; passageways for gas film damping in the fixed members that do not affect the capacitance to any significant degree; and provision for independently selecting two of the parameters sensitivity, capacitance and maximum acceleration.

Capacitive accelerometer with separable damping and sensitivity

A novel heterojunction acoustic charge transport device includes a transducer fabricated on a GaAs/AlGaAs heterojunction material that launches surface acoustic waver (SAW) along a transport channel. The device is characterized by a photodiode configured adjacent to the channel on the substrate to receive a modulated optical beam. An electrical signal equivalent is provided to a Schottky electrode at the end of the transport channel modulating the charge propagated by the surface acoustic wave. The modulated signal is output at a distal end of the transport channel.

Optically modulated acoustic charge transport device

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Glastonbury, CT, United States of America

Arthur G Foyt