MEMS sensor offset compensation with strain gauge

• US 9,625,329 B2
• Filed: 03/02/2015
• Issued: 04/18/2017
• Est. Priority Date: 03/02/2015
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Gurin, Ilya, Seeger, Joe
• Primary Examiner(s): Rogers, David A
• Application Number:
  US14/635,205
• Publication Number:
  US 20160258825A1
• Time in Patent Office: 778 Days
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/183 by measuring variations of frequency of vibrating piezo-resistive material
• CPC Class Codes: G01L 1/2293 of the semi-conductor type semi-conductor devices controllable by variations of applied mechanical force H01L29/84
• CPC Class Codes: G01L 27/002 Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination

Abstract

An example system comprises a microelectromechanical system (MEMS) sensor, a strain gauge, and a strain compensation circuit. The MEMS sensor is operable to generate a sensor output signal that corresponds to a sensed condition (e.g., acceleration, orientation, and/or pressure). The strain gauge is operable to generate a strain measurement signal indicative of a strain on the MEMS sensor. The strain compensation circuit is operable to modify the sensor output signal to compensate for the strain based on the strain measurement signal. The strain compensation circuit stores sensor-strain relationship data indicative of a relationship between the sensor output signal and the strain measurement signal. The strain compensation circuit is operable to use the sensor-strain relationship data for the modifying of the sensor output signal. The modification of the sensor output signal comprises one or both of: removal of an offset from the sensor signal, and application of a gain to the sensor signal.

Claims

1. A system comprising:

a microelectromechanical system (MEMS) sensor operable to generate a sensor output signal that corresponds to a sensed condition;

a strain gauge operable to generate a strain measurement signal indicative of a strain on the MEMS sensor, wherein the strain gauge and MEMS sensor are mechanically coupled via one or more anchor points; and

a strain compensation circuit, wherein the strain compensation circuit is operable to modify the sensor output signal to compensate for the strain based on the strain measurement signal.

2. The system of claim 1, wherein:

the strain compensation circuit stores sensor-strain relationship data indicative of a relationship between the sensor output signal and the strain measurement signal; and

the strain compensation circuit is operable to use the sensor-strain relationship data for the modification of the sensor output signal.

3. The system of claim 2, wherein the strain compensation stores the sensor-strain relationship data in a non-volatile memory.

4. The system of claim 1, wherein the modification of the sensor output signal comprises one or both of:

removal of an offset from the sensor signal, and application of a gain to the sensor signal.

5. The system of claim 1, wherein the modification of the sensor output signal is based, at least in part, on a piecewise linear relationship between strain and an offset and/or between strain and a gain.

6. The system of claim 1, wherein the strain gauge is a piezoresistive strain gauge.

7. The system of claim 1, wherein the strain gauge is a strain-sensitive MEMS resonator comprising a resonating member, an excitation plate, and a sustaining amplifier.

8. The system of claim 7, wherein the resonating member is a beam or diaphragm.

9. The system of claim 1, wherein the MEMS sensor comprises a base substrate coupled to a handle substrate.

10. The system of claim 9, wherein the base substrate is bonded to the handle substrate.

11. The system of claim 10, wherein the base substrate is bonded to the handle substrate utilizing a eutectic bond.

12. The system of claim 10, wherein the base substrate is bonded to the handle substrate in a manner that provides an electrical connection between an actuator of the MEMS sensor and the base substrate.

13. The system of claim 9, wherein the base substrate comprises electrical circuits.

14. The system of claim 9, wherein the base substrate comprises non-volatile memory.

15. The system of claim 9, wherein the strain gauge is formed in the base substrate.

16. The system of claim 1, wherein the MEMS sensor and the strain gauge are formed on a same substrate.

17. The system of claim 1, wherein the condition is one or more of:

acceleration, orientation, angular rate, and pressure.

18. A method comprising:

generating, by a microelectromechanical system (MEMS) sensor, a sensor output signal that corresponds to a sensed condition;

generating, by a strain gauge, a strain measurement signal indicative of a strain on the MEMS sensor, wherein the strain gauge and MEMS sensor are mechanically coupled via one or more anchor points; and

modifying, by a strain compensation circuit, the sensor output signal to compensate for the strain based on the strain measurement signal.

19. The method of claim 18, comprising:

storing, by the strain compensation circuit, sensor-strain relationship data indicative of a relationship between the sensor output signal and the strain measurement signal; and

performing the modifying based on the sensor-strain relationship data.

20. The method of claim 18, wherein the modifying the sensor output signal comprises one or both of:

removing an offset from the sensor signal, and applying a gain to the sensor signal.

21. The system of claim 18, wherein the modification of the sensor output signal is based, at least in part, on a piecewise linear relationship between strain and an offset and/or between strain and a gain.

22. The method of claim 18, wherein the strain gauge is a piezoresistive strain gauge.

23. The method of claim 18, wherein the strain gauge is a strain-sensitive MEMS resonator comprising a resonating member, an excitation plate, and a sustaining amplifier.

24. The method of claim 23, wherein the resonating member is a beam or diaphragm.

25. The method of claim 18, wherein the strain gauge resides in an integrated circuit die to which the MEMS sensor is mounted.

26. The method of claim 18, wherein the condition is one or more of:

acceleration, orientation, angular rate, and pressure.

27. A method comprising:

applying a mechanical stress to a MEMS sensor; and

while applying the mechanical stress to the MEMS sensor;

monitoring, by a strain characterization circuit, an output signal of a strain gauge coupled to the MEMS sensor, wherein the strain gauge and MEMS sensor are mechanically coupled via one or more anchor points;

monitoring, by the strain characterization circuit, an output signal of the MEMS sensor;

determining, by the strain characterization circuit, a relationship between the output signal of the strain gauge and the output signal of the MEMS sensor; and

storing, in a strain compensation circuit, data indicative of the relationship between the output signal of the strain gauge and the output signal of the MEMS sensor.

28. The method of claim 27, comprising:

performing by said strain compensation circuit;

modifying the output signal of the MEMS sensor to compensate for strain based on the stored data indicative of the relationship between the output signal of the strain gauge and the output signal of the MEMS sensor.