BMEMS-type high-sensitivity inertial sensor and manufacturing process thereof

• US 7,270,003 B2
• Filed: 07/25/2005
• Issued: 09/18/2007
• Est. Priority Date: 07/29/2004
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Baldo, Lorenzo, Del Sarto, Marco, Sassolini, Simone, Marchi, Mauro
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/189,544
• Publication Number:
  US 20060042385A1
• Time in Patent Office: 785 Days
• Field of Search: 735/143.2, 735/143.6, 735/143.8, 735/041.2, 735/041.4, 735/041.5, 735/040.4, 735/142.9
• US Class Current: 73/514.32
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings

Abstract

The semiconductor inertial sensor is formed by a rotor element and a stator element electrostatically coupled together. The rotor element is formed by a suspended mass and by a plurality of mobile electrodes extending from the suspended mass. The stator element is formed by a plurality of fixed electrodes facing respective mobile electrodes. The suspended mass is supported by elastic suspension elements. The suspended mass has a first, larger, thickness, and the elastic suspension elements have a second thickness, smaller than the first thickness.

Claims

1. A semiconductor inertial sensor, comprising:

a fixed region;

a rotor element having a first semiconductor layer, an intermediate layer positioned on the first semiconductor layer, and a second semiconductor layer positioned on the intermediate layer; and

a stator element formed from the first semiconductor layer and electrostatically coupled to the rotor element, said rotor element comprising a suspended mass carried by said fixed region via elastic suspension elements formed in said first semiconductor layer, said suspended mass having a first thickness and said elastic suspension elements having a second thickness, different from said first thickness.

2. The semiconductor inertial sensor according to claim 1 wherein said first thickness is greater than said second thickness.

3. The semiconductor inertial sensor according to claim 1, comprising a supporting substrate arranged directly underneath said rotor element, wherein said rotor element directly faces said substrate and is arranged at a distance therefrom via an air gap.

4. The semiconductor inertial sensor according to claim 1 wherein said rotor element comprises a plurality of mobile electrodes extending from said suspended mass, and said stator element comprising a plurality of fixed electrodes facing respective said mobile electrodes, said mobile electrodes having said first thickness and said fixed electrodes having said second thickness.

5. The semiconductor inertial sensor according to claim 4 wherein said sensor is a translational type sensor, and wherein said suspended mass has a polygonal shape with at least two first opposite sides and two second opposite sides, said mobile electrodes extending from said first opposite sides and said elastic suspension elements extending from said second opposite sides, and said fixed electrodes facing said mobile electrodes.

6. The semiconductor inertial sensor according to claim 4 wherein said sensor is a rotational type sensor, and wherein said suspended mass has a circular shape, said mobile electrodes extending radially from said suspended mass and said fixed electrodes extending radially towards said suspended mass, comb-fingered to said mobile electrodes, said elastic suspension elements extending in a generally radial direction between said suspended mass and said fixed region.

15. The semiconductor inertial sensor according to claim 1 wherein the intermediate layer is a dielectric layer.

7. A micro-electro-mechanical device, comprising:

a semiconductor substrate;

a rotor having a suspended mass a first thickness positioned in a spaced-apart relationship with the substrate wherein the semiconductor substrate extends directly below the suspended mass; and

an elastic suspension element having a second thickness, different from the first thickness, coupled between the rotor and the substrate wherein the rotor includes portions of first and second semiconductor material layers formed on the substrate, and the suspension element includes a portion of the first semiconductor material layer.

8. The device of claim 7, further comprising a detector circuit configured to detect movement of the rotor, relative to the substrate, along an axis lying parallel to a face of the substrate.

9. The device of claim 8 wherein the detector circuit is formed in the substrate.

10. The device of claim 8, further comprising a stator rigidly coupled to the substrate, and wherein the detector circuit is configured to detect changes in capacitive coupling between the rotor and the stator.

16. The system of claim 7 wherein the rotor includes a the first semiconductor material layer, an intermediate layer positioned on the first semiconductor material layer, and the second semiconductor material layer positioned on the intermediate layer.

17. The system of claim 16 wherein the intermediate layer is a dielectric layer.

11. A system, comprising:

an inertial sensor formed on a semiconductor material substrate, the inertial sensor including;

a rotor having a suspended mass in a spaced-apart relationship with a surface of the substrate wherein the surface of the substrate extends directly below the suspended mass, the rotor having a first thickness,

a stator rigidly coupled to the substrate, and

a spring element having a second thickness, different from the first thickness, the spring element coupled between the rotor and the substrate wherein the rotor includes a first semiconductor layer, an intermediate layer positioned on the first semiconductor layer, and a second semiconductor layer positioned on the intermediate layer.

12. The system of claim 11, further comprising:

an apparatus including a standby function; and

a detector circuit coupled to the inertial sensor and configured to initiate a restoration of functionality of the apparatus upon detection of movement by the sensor.

13. The system of claim 11, further comprising:

an automobile; and

a detector circuit coupled to the inertial sensor and configured to detect movement of the automobile.

14. The system of claim 11 wherein the intermediate layer is a dielectric layer.