Micro-electro-mechanical acceleration sensor device

Patent metadata

Field	Value
Publication number	US-2016274141-A1
Application number	US-201514980735-A
Country	US
Kind code	A1
Filing date	Dec 28, 2015
Priority date	Mar 20, 2015
Publication date	Sep 22, 2016
Grant date	—

Abstract

A MEMS acceleration device for measurement of the acceleration along three axes. The device includes capacitors, which capacitance changes under the influence of an acceleration acting upon the device. The change of capacitance for acceleration parallel to the substrate are, normally used with distinct capacitors. This device combines capacitors for using the change in capacitance for sensing in two independent and different directions parallel to the substrate thereby reusing the capacitor. Thereby allowing shrinking of the device while maintaining substantially the same sensitivity.

First claim

1 . A micro-electro-mechanical acceleration sensor device, the device comprising:
a substrate having a first substrate surface and a substrate plane; and a movable body having a first movable body surface;
wherein the first substrate surface and the first movable body surface are configured to constitute a first capacitor having a first capacitance;
wherein the movable body is configured to undergo a first displacement relative to the substrate plane in response to a first acceleration, the first displacement changing the first capacitance;
wherein the first displacement is parallel to the substrate plane;
wherein the first displacement has a first angle relative to the first substrate surface and is parallel to the substrate plane;
wherein the first angle is oblique to the first substrate surface; and
wherein the first capacitor is configured to yield a maximum change of the first capacitance in response to the first displacement.

2 . The device according to claim 1 ,
wherein the substrate has a second substrate surface;
wherein the movable body has a second movable body surface;
wherein the second substrate surface and the second movable body surface are configured to constitute a second capacitor having a second capacitance;
wherein the movable body is configured to undergo a second displacement relative to the substrate in response to a second acceleration, the second displacement changing the second capacitance;
wherein the second displacement has a second angle relative to the first substrate surface and is parallel to the substrate plane;
wherein the second angle is oblique to the first substrate surface;
wherein the second capacitor is configured to yield a maximum change of the second capacitance in response to the second displacement; and
wherein the first and second angles are different.

3 . The device according to claim 2 ,
wherein the substrate has a third substrate surface;
wherein the movable body has a third movable body surface;
wherein the third substrate surface and the third movable body surface are configured to constitute a third capacitor having a third capacitance; and
wherein the third capacitor is configured to have the third capacitance changed in an opposite direction with respect to the first capacitance.

4 . The device according to claim 3 ,
wherein the substrate has a fourth substrate surface;
wherein the movable body has a fourth movable body surface;
wherein the fourth substrate surface and the fourth movable body surface are configured to constitute a fourth capacitor having a fourth capacitance; and
wherein the fourth capacitor is configured to have the fourth capacitance changed in an opposite direction with respect to the second capacitance.

5 . The device according to claim 4 , wherein the first and second displacement are perpendicular.

6 . The device according to claim 1 ;
wherein the movable body is configured to undergo the first displacement and depended on claim 2 second displacement, which are composed of a translation or rotation parallel to the substrate plane.

7 . The device according to claim 6 , wherein the pivot axis of said rotation is perpendicular to the substrate.

8 . The device according to claim 7 , wherein the movable body has a centre of mass placed at a distance from the pivot axis.

9 . The device according to claim 1 ,
wherein the substrate has a fifth substrate surface;
wherein the movable body has a fifth movable body surface;
wherein the fifth substrate surface and the fifth movable body surface are configured to constitute a fifth capacitor having a fifth capacitance;
wherein the movable body is configured to undergo a third displacement relative to the substrate in response to a third acceleration, the third displacement changing the fifth capacitance; and
wherein the third displacement is perpendicular to the substrate plane.

10 . The device according to claim 4 , wherein, when the movable body is not subjected to an acceleration, the first capacitance and the second capacitance are configured to be equal.

11 . The device according to claim 10 , wherein, when the movable body is not subjected to an acceleration, the first capacitor and the fourth capacitor are configured to have equal capacitances.

12 . The device according to claim 2 , wherein the movable body surfaces are electrically coupled.

13 . A micro-electromechanical system comprising:
a first device according to claim 1 ; a first excitation circuit configured for a first electrical excitation of at least one surface of the first capacitor of the first device; and a first measuring circuit configured for measuring a first electrical result of said first excitation on another surface of the first capacitor of the first device.

14 . The system according to claim 13 , comprising a second device according to claim 1 , wherein the first displacement of the first device is independent of the first displacement of the second device.

15 . A method for measuring acceleration using a system comprising a sensor device comprising:
selecting a first excitation surface from the group of a substrate surface and a first movable body surface, thereby defining the other surface as a first sensing surface,
wherein the sensor device comprises a substrate having the first substrate surface and a movable body having the first movable body surface;
placing the first excitation surface at a reference voltage;
exciting the first excitation surface with a first excitation voltage; and
measuring a first charge change from the first sensing surface from said placing to said exciting for measuring a first acceleration,

wherein the first substrate surface and the first movable body surface are configured to constitute a first capacitor having a first capacitance;
wherein the substrate further has a substrate plane;
wherein the movable body is configured to undergo a first displacement relative to the substrate plane, in response to a first acceleration, the first displacement changing the first capacitance;
wherein the first displacement has a first angle relative to the first substrate surface parallel to the substrate plane;
wherein the first angle is oblique to the first substrate surface; and
wherein the first displacement yields a maximum change of the first capacitance.

16 . The method for measuring acceleration using the system according to claim 15 further comprising:
further selecting a second excitation surface being a second substrate surface in case the first substrate surface is selected as the first excitation surface or otherwise a second movable body surface and thereby defining the other surface as a second sensing surface;

wherein the substrate further comprises the second substrate surface and the movable body further comprises the second movable body surface; and
wherein the first and second sensing surfaces are electrically conductively coupled;
further placing the second excitation surface at the reference voltage at the same time as the first excitation surface is placed at the reference voltage;
further exciting the second excitation surface with the first excitation voltage at the same time as the first excitation surface is excited with the first excitation voltage;
second exciting the first excitation surface with a second excitation voltage and the second excitation sur

Assignees

• Freescale Semiconductor Inc

Inventors

• Enjalbert Jerome Romain

Classifications

• G01P2015/0831

  the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration · CPC title

• G01P15/18

  in two or more dimensions · CPC title

• G01P15/125 Primary

  by capacitive pick-up · CPC title