Planar inertial sensor, in particular for portable devices having a stand-by function

• US 20050274184A1
• Filed: 09/23/2004
• Published: 12/15/2005
• Est. Priority Date: 09/26/2003
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Lasalandra, Ernesto, Merassi, Angelo, Zerbini, Sarah, Vigna, Benedetto
• Granted Patent: US 7,252,002 B2
• Time in Patent Office: Days
• US Class Current: 73/514.10
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0857 using a particular shape of the suspension spring
• CPC Class Codes: H04M 2250/12 including a sensor for measuring a physical value, e.g. temperature or motion telephones including GPS signal receivers H04M2250/10

Abstract

A planar inertial sensor includes a first region and a second region of semiconductor material. The second region is capacitively coupled, and mobile with respect to the first region. The second region extends in a plane and has second portions, which face respective first portions of the first region. Movement of the second region, relative to the first region, in any direction belonging to the plane modifies the distance between the second portions and the first portions, which in turn modifies a value of the capacitive coupling.

Claims

1. An inertial sensor, comprising:

a first region of semiconductor material, said first region being fixed; and

a second region of semiconductor material, said second region being mobile and facing, at least in part, said first region, said second region extending in a plane, and said second region being translatable with respect to said first region in any direction belonging to said plane.

2. The inertial sensor according to claim 1 wherein said first and second regions are capacitively coupled to one another and have first and, respectively, second portions facing one another, said second portions being mobile with respect to said first portions so as to modify the distance between them in case of translation of said second region with respect to said first region in said direction belonging to said plane.

3. The inertial sensor according to claim 2 wherein said first and second regions have a basically circular shape and said first and second portions are shaped like the arc of a circumference.

4. The inertial sensor according to claim 1 wherein said first region is formed by a first plurality of arc-shaped regions, said arc-shaped regions of said first plurality being arranged on concentric circumferences, said second region being formed by a second plurality of arc-shaped regions, said arc-shaped regions of said second plurality being arranged on concentric circumferences, each said arc-shaped region of said first plurality facing a respective arc-shaped region of said second plurality.

5. The inertial sensor according to claim 4 wherein said arc-shaped regions of said second region arranged on a same circumference are connected together to form a plurality of concentric circumferences connected to one another through radial-connection arms.

6. The inertial sensor according to claim 1 wherein said second region is supported by a central anchorage.

7. The inertial sensor according to claim 6 wherein said second region has a central opening and said central anchorage comprises a pin element extending in said central opening and a plurality of spiral springs extending between said pin element and said second region.

8. The inertial sensor according to claim 1 wherein said first and second regions have a substantially elliptical shape.

9. The inertial sensor according to claim 1 wherein said first and second regions have a substantially polygonal shape.

10. The inertial sensor according to claim 2 wherein a capacitive value of the capacitive coupling between the first and second regions varies in accordance with a distance of translation of the second region with respect to first region, and wherein the variation is substantially independent of a direction of translation belonging to said plane.

11. A portable electronic apparatus comprising:

a device for re-activation from stand-by, said device for re-activation from stand-by including an inertial sensor having a first region of semiconductor material, said first region being fixed, and a second region of semiconductor material, said second region being mobile and facing, at least in part, said first region, said second region extending in a plane, and said second region being translatable with respect to said first region in any direction belonging to said plane.

12. A device, comprising:

a support substrate;

a stator region formed on the substrate; and

a rotor region movably coupled to the substrate such that the rotor region is free to move in any direction lying in a plane parallel to a surface of the substrate, the rotor region being capacitively coupled to the stator region such that displacement of the rotor a given distance in any direction lying in the plane changes the capacitive coupling to a degree substantially equal to a change of the coupling resulting from displacement of the rotor the same distance in any other direction lying in the plane.

13. The device of claim 12 wherein the support substrate is a first semiconductor material layer, and wherein the stator region and rotor region are formed in a second semiconductor material layer formed on the first semiconductor material layer.

14. The device of claim 12, comprising:

a detection circuit including a capacitor formed by the capacitive coupling and configured to detect changes of the capacitive coupling that exceed a selected threshold.

15. The device of claim 14 wherein the detection circuit is configured to bring a system from standby to active when the selected threshold is exceeded.

16. The device of claim 12 wherein:

the rotor is radially symmetrical, in plan view; and

the stator includes a sensor region surrounding the rotor, in plan view, and capacitively coupled thereto.

17. The device of claim 16 wherein:

the rotor has a substantially annular shape; and

wherein the rotor is movably coupled to the substrate via a plurality of springs surrounded by the annular shaped rotor and mechanically coupled at respective first ends to the rotor and at respective second ends to the substrate.

18. The device of claim 16 wherein:

the rotor comprises a plurality of rotor electrodes mechanically coupled to the rotor in concentric rings; and

the sensor region comprises a plurality of sensor electrodes facing respective ones of the plurality of rotor electrodes.

19. The device of claim 18 wherein each of the plurality of sensor electrodes is coupled to a common node.

20. The device of claim 16 wherein the rotor has a polygonal shape, in plan view.

21. The device of claim 16 wherein the rotor has a substantially circular shape, in plan view.

22. A device, comprising:

an electronic system; and

detection means for detecting when acceleration of the electronic system in any direction lying in a plane exceeds a selected acceleration threshold, the threshold being substantially equal with respect to acceleration in any direction lying in the plane.

23. The device of claim 22 wherein the electronic system comprises a cellular telephone.

24. The device of claim 22 wherein the electronic system comprises a hand-held video game.

25. The device of claim 22 wherein the electronic system comprises a palm-top computer.

26. The device of claim 22 wherein the electronic system comprises a calculator.

27. A method, comprising:

displacing a rotor within a plane, a distance relative to a stator; and

varying a capacitive coupling between the rotor and the stator in direct relation to the distance the rotor is displaced, a magnitude of the variation being substantially independent of a direction of displacement of the rotor within the plane.

28. The method of claim 27 wherein the relationship between the distance of displacement and magnitude of variation is non-linear.

29. The method of claim 27, comprising performing the displacing step in response to movement of an electronic device.