ACCELEROMETRIC SENSOR IN MEMS TECHNOLOGY HAVING HIGH ACCURACY AND LOW SENSITIVITY TO TEMPERATURE AND AGEING

• US 20170285061A1
• Filed: 09/29/2016
• Published: 10/05/2017
• Est. Priority Date: 03/31/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Tocchio, Alessandro, Rizzini, Francesco, Valzasina, Carlo, Langfelder, Giacomo
• Granted Patent: US 10,591,505 B2
• Time in Patent Office: Days
• CPC Class Codes: G01P 1/006 used for thermal compensation
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum
• CPC Class Codes: G01P 2015/0834 the mass constituting a pendulum having the pivot axis disposed symmetrically between the longitudinal ends, the center of mass being shifted away from the plane of the pendulum which includes the pivot axis

Abstract

The accelerometric sensor has a suspended region, mobile with respect to a supporting structure, and a sensing assembly coupled to the suspended region and configured to detect a movement of the suspended region with respect to the supporting structure. The suspended region has a geometry variable between at least two configurations associated with respective centroids, different from each other. The suspended region is formed by a first region rotatably anchored to the supporting structure and by a second region coupled to the first region through elastic connection elements configured to allow a relative movement of the second region with respect to the first region. A driving assembly is coupled to the second region so as to control the relative movement of the latter with respect to the first region.

Claims

1. An integrated MEMS accelerometric sensor, comprising:

a supporting structure;

a suspended region mobile with respect to the supporting structure; and

a sensing assembly coupled to the suspended region and configured to detect a movement of the suspended region with respect to the supporting structure;

wherein the suspended region has a variable geometry.

2. The accelerometric sensor according to claim 1, wherein the suspended region has a geometry variable between at least first and second configurations, the suspended region having a centroid in a first position in the first configuration, the centroid being in a second position in the second configuration, the first and second positions being different from each other.

3. The accelerometric sensor according to claim 2, wherein the suspended region comprises a first region rotatably anchored to the supporting structure, a second region coupled to the first region, and elastic connection elements coupling the second region to the first region and configured to allow a relative movement of the second region with respect to the first region;

the accelerometric sensor further comprising a driving assembly coupled to the second region and configured to control the relative movement.

4. The accelerometric sensor according to claim 3, wherein the driving assembly is a capacitive driving assembly and comprises driving electrode pairs facing each other and causing a roto-translation movement of the second region with respect to the first region.

5. The accelerometric sensor according to claim 3, further comprising:

a driving source configured to supply the driving assembly with a first driving voltage in a first sensing step and with a second driving voltage in a second sensing step; and

a processing circuit including;

a conversion interface coupled to the sensing assembly and configured to generate a first position-measure signal in the first sensing step and a second position-measure signal in the second sensing step; and

a subtractor configured to receive the first and second position-measure signals and generate an acceleration signal as a difference between the first and second position-measure signals.

6. The accelerometric sensor according to claim 3, further comprising:

a driving source configured to supply an ac driving voltage to the driving assembly; and

a processing circuit including;

an conversion interface coupled to the sensing assembly and configured to generate an ac position-measure signal;

a high-pass filter coupled to an output of the conversion interface; and

a demodulator coupled to an output of the high-pass filter.

7. The accelerometric sensor according to claim 6, wherein the suspended region and the supporting region are formed in a first semiconductor material die and the processing circuit is formed in a second semiconductor material die.

8. The accelerometric sensor according to claim 3, wherein the first and second regions are of a same monolithic semiconductor layer.

9. The accelerometric sensor according to claim 3, wherein the second region comprises a frame that laterally envelops the first region.

10. The accelerometric sensor according to claim 2, wherein the sensing assembly is a capacitive sensing assembly and comprises at least two sensing electrodes facing each other.

11. The accelerometric sensor according to claim 2, wherein the accelerometric sensor is an in-plane acceleration sensor that includes elastic suspension elements that anchor the suspended region to the supporting structure and are configured to allow rotation of the suspended region about a rotation axis perpendicular to the suspended region.

12. The accelerometric sensor according to claim 2, wherein the accelerometric sensor is out-of-plane acceleration sensor that includes elastic suspension elements that anchor the suspended region to the supporting structure and are configured to allow rotation of the suspended region about a rotation axis parallel to the suspended region.

13. A method for detecting an external acceleration, comprising:

driving a suspended region, mobile with respect to a supporting structure, so that the suspended region has at least one first geometrical configuration in a first sensing step and a second geometrical configuration in a second sensing step, the first and second geometrical configurations being different from each other;

acquiring first and second position measure signals correlated to a first position of the suspended region in the first step and to a second position of the suspended region in the second step, respectively; and

processing the first and second position-measure signals and generating an accelerometric signal independent of spurious displacements of the suspended region with respect to the supporting structure.

14. The method according to claim 13, wherein the suspended region comprises a first region rotatably anchored to the supporting structure and a second region coupled to the first region through elastic connection elements configured to allow a relative movement of the second region with respect to the first region;

and wherein driving the suspended region comprises applying a variable driving voltage to a driving assembly coupled to the second region.

15. The method according to claim 14, wherein applying the variable driving voltage comprises supplying a first driving voltage in the first step and a second driving voltage in the second step, the method further comprising:

generating an acceleration signal as a difference between the first and second position-measure signals.

16. The method according to claim 14, wherein applying the variable driving voltage comprises supplying an ac driving voltage, and the first and second position-measure signals are samples of an ac measure signal, the method further comprising:

filtering the ac measure signal with a high-pass filter for generating a filtered signal without dc components; and

demodulating the filtered signal.

17. An integrated MEMS accelerometric sensor, comprising:

a supporting structure;

a suspended region mobile with respect to the supporting structure, wherein the suspended region has a geometry variable between first and second configurations and the suspended region comprises a first region coupled to the supporting structure, a second region coupled to the first region, and elastic connection elements coupling the second region to the first region and configured to allow a relative movement of the second region with respect to the first region;

a sensing assembly coupled to the suspended region and configured to detect a movement of the suspended region with respect to the supporting structure; and

a driving assembly coupled to the second region and configured to control the relative movement of the second region with respect to the first region.

18. The accelerometric sensor according to claim 17, wherein the driving assembly is a capacitive driving assembly and comprises driving electrode pairs facing each other and causing a roto-translation movement of the second region with respect to the first region.

19. The accelerometric sensor according to claim 17, further comprising:

a driving source configured to supply the driving assembly with a first driving voltage in a first sensing step and with a second driving voltage in a second sensing step; and

a processing circuit including;

a conversion interface coupled to the sensing assembly and configured to generate a first position-measure signal in the first sensing step and a second position-measure signal in the second sensing step; and

a subtractor configured to receive the first and second position-measure signals and generate an acceleration signal as a difference between the first and second position-measure signals.

20. The accelerometric sensor according to claim 17, further comprising:

a driving source configured to supply an ac driving voltage to the driving assembly; and

a processing circuit including;

an conversion interface coupled to the sensing assembly and configured to generate an ac position-measure signal;

a high-pass filter coupled to an output of the conversion interface; and

a demodulator coupled to an output of the high-pass filter.