| 摘要 |
A shear stress sensor is fabricated using wafer bonding technology. The shear stress sensor is a floating element shear stress sensor designed to measure shear stresses of about 1 kPa-100 kPa over a wide range of operating conditions (temperature, humidity), as well as for a large variety of fluids. The sensor employs a silicon plate suspended about 1.4 microns above the surface of a silicon substrate by piezoresistive arms. The arms are directed parallel to the flow of interest and are loaded in tensile or compressive stress. The piezoresistive arms convert the strain to an electrical output which can be configured in a half bridge circuit with appropriate wiring. Fabrication of the sensor includes bonding a substrate silicon wafer and a device wafer which has an epitaxial silicon layer grown on top of a p+ dopant layer. The device wafer is etched back using the p+ layer as an etch stop. After selective removable of the p+ layer, ohmic contacts are formed through implantation and metalization techniques. Plasma etching of the epitaxial silicon layer releases the sensor plate. A PECVD oxide is used to define the geometric characteristics of the plate and arms and to passivate the wafer chip.
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