High temperature piezoresistive strain gauges made of silicon-on-insulator

Abstract

Disclosed is an apparatus for measuring a parameter in a borehole penetrating the earth. The apparatus includes a sensor configured to be disposed in the borehole and having a piezo-resistor fabricated from a semiconductor on an insulator wherein a portion of the semiconductor is etched to the insulator to form the piezo-resistor, the piezo-resistor being responsive to the parameter.

What is claimed is: 
     
         1 . An apparatus for measuring a parameter in a borehole penetrating the earth, the apparatus comprising:
 a sensor configured to be disposed in the borehole and having a piezo-resistor fabricated from a semiconductor on an insulator wherein a portion of the semiconductor is etched to the insulator to form the piezo-resistor, the piezo-resistor being responsive to the parameter.   
     
     
         2 . The apparatus according to  claim 1 , wherein the piezo-resistor comprises a plurality of piezo-resistors. 
     
     
         3 . The apparatus according to  claim 2 , wherein the plurality of piezo-resistors comprises a network. 
     
     
         4 . The apparatus according to  claim 3 , wherein the network comprises an electrical bridge. 
     
     
         5 . The apparatus according to  claim 4 , wherein the electrical bridge comprises a Wheatstone bridge. 
     
     
         6 . The apparatus according to  claim 1 , wherein the semiconductor is doped with n-type or p-type doping material up to a degeneration region of the semiconductor. 
     
     
         7 . The apparatus according to  claim 1 , wherein the semiconductor comprises silicon and the insulator comprises silicon dioxide. 
     
     
         8 . The apparatus according to  claim 1 , further comprising an electrical signal source coupled to the piezo-resistor to energize the piezo-resistor. 
     
     
         9 . The apparatus according to  claim 1 , further comprising an amplifier coupled to the piezo-resistor and configured to amplify an output signal corresponding to the measured parameter. 
     
     
         10 . The apparatus according to  claim 1 , wherein the parameter is at least one of acceleration, force, tilt, contact, pressure, strain, stress, and magnetic field fluctuations. 
     
     
         11 . The apparatus according to  claim 10 , wherein the sensor is configured as a Hall sensor. 
     
     
         12 . The apparatus according to  claim 10 , wherein the parameter is related to a property of an earth formation penetrated by the borehole. 
     
     
         13 . The apparatus according to  claim 1 , wherein the semiconductor is on a first insulator separated from a second insulator. 
     
     
         14 . An apparatus for measuring a parameter in a borehole penetrating the earth, the apparatus comprising:
 a carrier configured to be conveyed through the borehole; and   a sensor disposed at the carrier and having a piezo-resistor fabricated from a semiconductor on an insulator wherein a portion of the semiconductor is etched to the insulator to form the piezo-resistor, the piezo-resistor being responsive to the downhole parameter.   
     
     
         15 . The apparatus according to  claim 14 , wherein the carrier is a drill string. 
     
     
         16 . A method for measuring a parameter in a borehole penetrating the earth, the method comprising:
 disposing a sensor into the borehole, the sensor having a piezo-resistor fabricated from a semiconductor on an insulator wherein a portion of the semiconductor is etched to the insulator to form the piezo-resistor, the piezo-resistor being responsive to the parameter; and   measuring the parameter using the sensor.   
     
     
         17 . The method according to  claim 16 , further comprising energizing the piezo-resistor with an input electrical signal. 
     
     
         18 . The method according to  claim 17 , further comprising receiving an output electrical signal due to the energizing wherein the output electrical signal relates to the measured parameter. 
     
     
         19 . The method according to  claim 16 , further comprising at least one of recording the measured parameter, transmitting the measured parameter to downhole electronics, or transmitting the measured parameter to a processing system disposed at the surface of the earth. 
     
     
         20 . The method according to  claim 15 , wherein the parameter is at least one of acceleration, force, tilt, contact, pressure, strain, stress, and magnetic field fluctuations. 
     
     
         21 . The method according to  claim 19 , wherein the parameter is related to a property of an earth formation penetrated by the borehole. 
     
     
         22 . The method according to  claim 16 , wherein the semiconductor is on a first insulator separated from a second insulator.