Media-compatible electrically isolated pressure sensor for high temperature applications

Abstract

A pressure sensor is described with sensing elements electrically and physically isolated from a pressurized medium. An absolute pressure sensor has a reference cavity, which can be at a vacuum or zero pressure, enclosing the sensing elements. The reference cavity is formed by bonding a recessed cap wafer with a gauge wafer having a micromachined diaphragm. Sensing elements are disposed on a first side of the diaphragm. The pressurized medium accesses a second side of the diaphragm opposite to the first side where the sensing elements are disposed. A spacer'wafer may be used for structural support and stress relief of the gauge wafer. In one embodiment, vertical through-wafer conductive vias are used to bring out electrical connections from the sensing elements to outside the reference cavity. In an alternative embodiment, peripheral bond pads on the gauge wafer are used to bring out electrical connections from the sensing elements to outside the reference cavity. In various embodiments, a regular silicon-on-insulator wafer or a double silicon-on-insulator wafer may be used as the gauge wafer, and appropriate micromachining steps are adopted to define the diaphragm. A layer of corrosion resistant material is deposited on the surface of the diaphragm that is accessed by the pressurized medium.

Description

technical field [0001] The present invention relates generally to pressure sensing devices and, more particularly, to pressure sensing elements in malignant and / or electrically conductive pressurized media at elevated temperatures. Background technique [0002] Diaphragm pressure sensors have been widely used in which pressure applied by a pressurized medium deflects a diaphragm, and a sensing element (such as a strain gauge) coupled to the diaphragm detects the deflection and provides feedback to correct the diaphragm. The inclined signal provides some pressure. [0003] There are two main types of pressure sensors. The first type is known as a differential pressure sensor, which measures pressure relative to atmospheric pressure. The second type is known as an absolute pressure sensor, which typically measures pressure relative to vacuum or zero pressure. [0004] Figures 1A and 1B illustrate a conventional differential pressure sensor 100 and a conventional absolute pr...

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Problems solved by technology

This method is complex and uses capacitive sensors and polysilicon connections

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