Transducer responsive to pressure, vibration/acceleration and temperature and methods of fabricating the same

• US 7,178,403 B2
• Filed: 12/03/2004
• Issued: 02/20/2007
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Kulite Semiconductor Products Inc
• Original Assignee: Kulite Semiconductor Products Inc
• Inventors: Kurtz, Anthony D.
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US11/004,327
• Publication Number:
  US 20060117860A1
• Time in Patent Office: 809 Days
• Field of Search: 737/19, 737/20, 737/21, 737/25, 737/26, 737/27, 737/54, 257/414, 361/283.4
• US Class Current: 73/754
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01L 19/0092 Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature G01L9/025, G01L9/045, G01L9/065, G01L9/085, G01L9/105, G01L9/125, G01L19/02, G01L19/04 take precedence; measuring two or more variable G01D21/02; temperature sensors with pressure compensation G01K1/26
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: G01L 9/0055 bonded on a diaphragm
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges

Abstract

A pressure sensing device produces an output proportional to applied pressure irrespective of vibration/acceleration of the device, which device also provides an output proportional only to vibration/acceleration of the device irrespective of the pressure.

Claims

1. A transducer responsive to applied pressure and vibration/acceleration comprising:

at least first and second sensor elements connected in series and responsive to an applied pressure and vibration to produce an output signal proportional to applied pressure and vibration/acceleration,

third, fourth, fifth and sixth sensor elements, said third and fourth elements connected in series, said fifth and sixth elements connected in series, said third, fourth, fifth and sixth sensor elements responsive only to said applied vibration/acceleration and non-responsive to said applied pressure,

said first and second sensor elements connected to said third and fourth elements to form a first array for providing an output directly proportional to pressure whereby applied vibration/acceleration is cancelled,

seventh and eighth elements connected in series and connected to said fifth and sixth elements to form a second array for providing an output responsive only to applied vibration/acceleration and non-responsive to applied pressure.

2. The transducer according to claim 1, wherein:

said first to said sixth sensor elements are each piezoresistive elements for providing a change in resistance according to an applied pressure or vibration/acceleration.

3. The transducer according to claim 2 wherein said seventh and eighth elements are fixed resistors.

4. The transducer according to claim 1 wherein said first and second arrays are each a Wheatstone bridge array.

5. The transducer according to claim 2 wherein said piezoresistors are semiconductor piezoresistors formed on a silicon substrate, with first and second piezoresistors positioned on a first deflecting diaphragm region of said substrate, which first deflecting diaphragm region is adapted to receive an applied pressure and an applied vibration/acceleration, with said third to sixth piezoresistive sensors positioned on a second deflecting diaphragm region on said substrate, which said second region is adapted only to receive an applied vibration/acceleration.

6. The transducer according to claim 5 wherein said seventh and eighth resistors are located on an inactive region of said wafer.

7. The transducer according to claim 4 further including:

a span resistor in series with the bias voltage input of said first Wheatstone bridge to provide an output across said span resistor proportional to the temperature of said bridge.

8. The transducer according to claim 7 wherein said first and second Wheatstone bridges are in close proximity to one another.

9. The transducer according to claim 5, further including a cover member coupled to said wafer and having a first aperture communicating with said first deflecting diaphragm region for enabling an applied pressure to deflect said first region, said cover member completely covering said second deflecting diaphragm region to prevent said applied pressure from deflecting said second diaphragm region, with both regions operative to deflect upon application of an applied vibration/acceleration.

10. The transducer according to claim 9 wherein said cover member is fabricated from glass.

11. A transducer responsive to an applied pressure, vibration/acceleration, comprising:

a semiconductor wafer having a first thin active area indicative of a first diaphragm deflecting region surrounded by an inactive wafer area, said wafer having a second thin active area indicative of a second diaphragm deflecting region also surrounded by an inactive wafer area,

first and second piezoresistive elements located on said first region and connected in series,

third, fourth, fifth and sixth piezoresistive elements located on said second region with said third and forth elements connected in series, and with said fifth and sixth elements connected in series,

said first and second elements connected to said third and fourth elements to form a first Wheatstone bridge array,

first and second resistors connected in series and positioned on an inactive area of said wafer, said first and second resistors connected to said fifth and sixth elements to form a second Wheatstone bridge array,

a cover member secured to said wafer and having an aperture communicating with said first deflecting region to apply a pressure to said first and second piezoresistor elements, said cover member completely covering said second deflecting region to prevent said second region from deflecting from said applied pressure, whereby said first and second regions both deflect upon application of an applied vibration/acceleration to cause said first bridge to provide an output voltage directly proportional to pressure only, whereby any vibration/acceleration component is cancelled and to cause said second bridge to provide an output voltage directly proportional to vibration/acceleration.

12. The transducer according to claim 11 further including a span resistor in series with the voltage input of said first bridge to provide an output across said span resistor indicative of the temperature of said wafer.

13. The transducer according to claim 11 wherein said wafer is fabricated from silicon.

14. The transducer according to claim 13 wherein said piezoresistors are formed on said wafer.

15. The transducer according to claim 14 wherein said piezoresistors are dielectrically isolated from said wafer.

16. The transducer according to claim 13 wherein said cover member is fabricated from glass.

17. The transducer according to claim 12 wherein said span resistor has a relatively zero temperature coefficient.

18. The transducer according to claim 11 wherein said first and second deflecting regions are relatively of the same thickness and area dimensions.

19. The transducer according to claim 11 wherein said piezoresistors are relatively of the same value.

20. The transducer according to claim 11 wherein said wafer is mounted on a metal shim.

21. The transducer according to claim 20 wherein said shim is fabricated from Kovar.