MEMS sensors, methods for providing same and method for measuring a fluid constituent

• US 10,641,626 B2
• Filed: 08/21/2018
• Issued: 05/05/2020
• Est. Priority Date: 08/23/2017
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Bretthauer, Christian, Dehe, Alfons, Makaram, Prashanth, Onaran, Abidin Guclu, Walther, Arnaud
• Primary Examiner(s): Dowtin, Jewel V
• Application Number:
  US16/106,247
• Publication Number:
  US 20190063968A1
• Time in Patent Office: 623 Days
• CPC Class Codes: G01F 1/363 with electrical or electro-mechanical indication G01F1/37 and G01F1/38 take precedence
• CPC Class Codes: G01F 1/383 with electrical or electro-mechanical indication
• CPC Class Codes: G01F 1/84 Coriolis or gyroscopic mass flowmeters
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal
• 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 9/0016 of a diaphragm
• CPC Class Codes: G01N 11/08 by measuring pressure required to produce a known flow
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/02809 Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/323 compensating for pressure or tension variations
• CPC Class Codes: G01N 29/326 compensating for temperature variations
• CPC Class Codes: G01N 33/0009 General constructional details of gas analysers, e.g. portable test equipment devices for withdrawing samples in the gaseous state G01N1/22

Abstract

In accordance with an embodiment, a MEMS sensor includes a membrane that is suspended from the substrate, a resonant frequency of said membrane being influenced by an ambient pressure that acts on the membrane; and an evaluation device configured to perform a first measurement based on the resonant frequency of the membrane to obtain a measurement result, where the evaluation device is configured to at least partly compensate an influence of the ambient pressure on the measurement result.

Claims

1. A MEMS sensor comprising:

a substrate;

a membrane that is suspended from the substrate, a resonant frequency of said membrane being influenced by an ambient pressure that acts on the membrane; and

an evaluation device which is configured to perform a first measurement based on the resonant frequency of the membrane to obtain a measurement result; and

wherein the evaluation device is configured to at least partly compensate an influence of the ambient pressure on the measurement result.

2. The MEMS sensor as claimed in claim 1, wherein the evaluation device is configured to at least partly compensate an influence of an ambient temperature acting on the membrane on the measurement result.

3. The MEMS sensor as claimed in claim 1, wherein the MEMS sensor is configured to perform a reference measurement before or after the first measurement to determine the ambient pressure that acts on the membrane and to provide a result of the reference measurement of the evaluation device.

4. The MEMS sensor as claimed in claim 1, wherein the evaluation device is configured to determine the ambient pressure based on a deflection of the membrane.

5. The MEMS sensor as claimed in claim 1, wherein the evaluation device is further configured to alternately in time perform a reference measurement based on an unresonant evaluation of a membrane position and perform the first measurement.

6. The MEMS sensor as claimed in claim 5, wherein the evaluation device is configured to use a result of the reference measurement to determine the ambient pressure and to perform a calibration with respect to the first measurement.

7. The MEMS sensor as claimed in claim 1, wherein the measurement result depends on an ambient fluid that interacts with the membrane, wherein the evaluation device is configured to resonantly excite the membrane to obtain an information item with respect to the ambient fluid.

8. The MEMS sensor as claimed in claim 1, wherein the evaluation device is embodied to take account of a concentration of a constituent of a fluid that interacts with the membrane on the basis of the rule

Δ

f(P,T,PPM)=Σ

_i=0ⁿΣ

_j=0ⁿΣ

_k=0ⁿa_i,j,kPⁱT^jPPM^k,

where Δ

f denotes a shift of the resonant frequency of the membrane obtained by the influence of an ambient temperature and the ambient pressure and ai,j,k denotes polynomial coefficients.

9. The MEMS sensor as claimed in claim 1, wherein the evaluation device is configured to provide a measurement signal based on a reference measurement for determining the ambient pressure and based on the first measurement, and the measurement signal has an information item with respect to the ambient pressure, an ambient temperature, and a fluid that interacts with the membrane.

10. The MEMS sensor as claimed in claim 1, wherein the membrane is configured to facilitate adsorption of a constituent of a fluid at the membrane, wherein the adsorption of the constituent causes a change in a mass of the membrane bringing about a resonance shift of a natural frequency of the membrane, and wherein the evaluation device is configured to output a measurement signal that has an information item with respect to the resonance shift.

11. The MEMS sensor as claimed in claim 10, wherein the membrane is a first membrane and the MEMS sensor has at least one second membrane, wherein the first and second membrane are configured for an adsorption of different constituents of the fluid.

12. The MEMS sensor as claimed in claim 1, wherein the MEMS sensor is formed in absence of a heating element for heating the membrane to reverse diffusion of a constituent of a fluid into the membrane.

13. The MEMS sensor as claimed in claim 1, wherein the evaluation device is configured to apply a changeable electric bias voltage to the membrane to set a changeable natural frequency of the membrane.

14. The MEMS sensor as claimed in claim 13, wherein the evaluation device is configured to change the changeable electric bias voltage based on a result of the first measurement.

15. The MEMS sensor as claimed in claim 13, wherein the evaluation device is configured to perform a reference measurement for determining the ambient pressure at a first value of the changeable electric bias voltage to obtain a first partial result and perform a further first measurement with a second value of the changeable electric bias voltage to obtain a second partial result, wherein the MEMS sensor is further configured to perform differential processing of the first partial result and of the second partial result to obtain a result of a second measurement.

16. The MEMS sensor as claimed in claim 1,

wherein the membrane is a first membrane which has a first sensitivity in respect of a constituent of a fluid, and the MEMS sensor further has a second membrane which has a second sensitivity in respect of the constituent of the fluid;

and

wherein the MEMS sensor is embodied to perform a first run-through of the first measurement using the first membrane and perform a second run-through of the first measurement using the second membrane, wherein the MEMS sensor is configured to perform differential processing of a result of the first run-through and of the second run-through to obtain a result of a second measurement.

17. The MEMS sensor as claimed in claim 16, wherein the first sensitivity and the second sensitivity form a quotient of a larger value and a smaller value, which is at least 1.1 and at most 10.

18. A MEMS sensor comprising:

a substrate;

a membrane that is suspended from the substrate; and

an evaluation device configured to alternately in time perform a reference measurement based on an unresonant evaluation of a membrane position and perform a first measurement based on a resonant frequency of the membrane.

19. The MEMS sensor as claimed in claim 18, configured to obtain a measurement result based on the first measurement, wherein the evaluation device is configured to determine an environmental influence that acts on the membrane on the basis of the reference measurement, and wherein the evaluation device is further configured to at least partly compensate the environmental influence on the measurement result.

20. The MEMS sensor as claimed in claim 18, wherein the evaluation device is configured to provide an information item with respect to an ambient pressure that acts on the membrane based on the reference measurement, and wherein the evaluation device is configured to take account of an influence of the ambient pressure on the resonant frequency of the membrane during the first measurement.

21. A MEMS sensor comprising:

a substrate;

a membrane that is suspended from the substrate; and

an evaluation device configured to perform a measurement using a deflection of the membrane;

wherein the evaluation device is configured to perform a first implementation of the measurement with a first membrane sensitivity of the membrane and a second implementation of the measurement with a second membrane sensitivity of the membrane or of a further membrane to obtain a combined result by combining a result of the first implementation and a result of the second implementation.

22. The MEMS sensor as claimed in claim 21, wherein the evaluation device is embodied to apply a first changeable electric bias voltage to the membrane for the first implementation to obtain the first membrane sensitivity and to apply a second electric bias voltage to the membrane for the second implementation to obtain the second membrane sensitivity.

23. The MEMS sensor as claimed in claim 21, wherein the membrane is a first membrane which has a first sensitivity in respect of a constituent of a fluid, and the MEMS sensor further has a second membrane that has a second sensitivity in respect of the constituent of the fluid;

and

wherein the MEMS sensor is configured to perform the first implementation of the measurement using the first membrane and is configured to perform the second implementation of the measurement using the second membrane, wherein the MEMS sensor is configured to perform differential processing of a result of the first implementation and the second implementation to obtain the combined result.

24. The MEMS sensor as claimed claim 21, wherein the first membrane sensitivity and the second membrane sensitivity form a quotient of a larger value and a smaller value, which is at least 1.1 and at most 10.

25. The MEMS sensor as claimed in claim 21, wherein the evaluation device is configured to at least partly compensate an environmental influence acting on the membrane on a result of the measurement.