Microelectromechanical structure insensitive to mechanical stresses

• US 6,508,124 B1
• Filed: 09/07/2000
• Issued: 01/21/2003
• Est. Priority Date: 09/10/1999
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Zerbini, Sarah, Vigna, Benedetto, Sassolini, Simone
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/657,294
• Time in Patent Office: 866 Days
• Field of Search: 735/140.1, 735/140.2, 735/141.6, 735/142.9, 735/143.2, 735/143.8, 735/041.2, 735/040.4
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A microelectromechanical structure includes a rotor element having a barycentric axis and suspended regions arranged a distance with respect to the barycentric axis. The rotor element is supported and biased via a suspension structure having a single anchoring portion extending along the barycentric axis. The single anchoring portion is integral with a body of semiconductor material on which electric connections are formed.

Claims

1. A microelectromechanical structure comprising a rotor element having a barycentric axis and including suspended regions arranged at a distance with respect to said barycentric axis, wherein said rotor element is connected to a single anchoring portion extending along said barycentric axis, wherein the microelectromechanical structure is an angular accelerometer, and said rotor element comprises a suspended mass of annular shape concentric with said barycentric axis and connected to said single anchoring portion through a suspension structure, said suspending mass bearing a plurality of mobile electrodes extending radially towards said barycentric axis and interleaved with a plurality of fixed electrodes.

2. The microelectromechanical structure according to claim 1, wherein in that said single anchoring portion is integral with a body of semiconductor material.

3. The microelectromechanical structure according to claim 1, wherein said suspension structure comprises suspended arms extending radially, at a uniform angular distance from each other, from said suspended mass towards a central anchoring element integral with said anchoring portion, said anchoring portion being integral with a substrate of semiconductor material.

4. The microelectromechanical structure according to claim 3, wherein said central anchoring element is in electrical contact, through said anchoring portion, with an electrical connection region extending over said substrate and beneath said rotor element;

said electrical connection region being isolated from said rotor element by an air gap region.

5. The microelectromechanical structure according to claim 1, wherein said rotor element is of semiconductor material.

6. A microelectromechanical structure, comprising:

a first plurality of stator elements; and

a rotor having a barycentric axis and including;

a central anchor portion through which the barycentric axis extends;

a first seismic mass separated from the central anchor portion;

a first plurality of mobile rotor elements interleaved with the plurality of stator elements, the rotor elements extending from and being supported by the first seismic mass; and

a first plurality of flexible support arms extending between the first and seismic mass and the central anchor portion, the support arms flexibly supporting the first seismic mass such that the seismic mass and rotor elements are movable coupled to the central anchor portion.

7. The microelectromechanical structure according to claim 6, further comprising:

a second seismic mass extending at a distance from the first seismic mass on an opposite side of said barycentric axis;

second and third pluralities of stator element; and

a suspension structure connected between said central anchor portion and said second seismic mass, said second seismic mass bearing second and third pluralities of mobile rotor elements, said second and third pluralities of mobile rotor elements extending from a different side of said second seismic mass and being interleaved with said second and third pluralities of stator elements, respectively.

8. The microelectromechanical structure according to claim 7, wherein said suspension structure comprises first spring elements extending perpendicularly to said seismic masses towards the central anchor portion, said central anchor portion being integral with a substrate of semiconductor material.

9. The microelectromechanical structure according to claim 8, wherein said central anchor portion is a beam element extending parallel to said seismic masses.

10. The microelectromechanical structure according to claim 7, wherein the microelectromechanical structure comprises a linear accelerometer.

11. The microelectromechanical structure according to claim 7, wherein the microelectromechanical structure comprises a gyroscope.

12. The microelectromechanical structure according to claim 7, wherein said suspension structure comprises a second plurality of flexible support arms connected between said central anchor portion and said second seismic mass;

each said flexible support arm of said second plurality of flexible support arms bearing fourth and fifth pluralities of mobile rotor elements, each plurality of the fourth and fifth pluralities of mobile rotor elements extending from a different side of a respective flexible support arm of said second plurality of support arms and being interleaved with a respective plurality of stator elements.

13. The microelectromechanical structure of claim 6 wherein the first seismic mass has an annular shape concentric with said barycentric axis and the support arms extend radially from the central anchor portion to the first seismic mass.

14. The microelectromechanical structure of claim 13 wherein the rotor elements extend radially inwardly from the first seismic mass to the central anchor portion.

15. The microelectromechanical structure of claim 13, further comprising:

an electrical connection region in contact with and extending from the central anchor portion to an electrical contact, the connection region extending beneath the first seismic mass and isolated from the first seismic mass by a first air gap, the rotor elements being electrically connected to the electrical contact through the first seismic mass, at least one of the support arms, the central anchor portion, and the connection region.

16. The microelectromechanical structure of claim 6 further comprising:

a second plurality of stator elements;

wherein the rotor further includes;

a second seismic mass positioned on an opposite side of the central anchor portion from the first seismic mass;

a second plurality of mobile rotor elements interleaved with the second plurality of stator elements, the second plurality of rotor elements extending from and being supported by the first seismic mass; and

a second plurality of flexible support arms extending between the second seismic mass and the central anchor portion, the second plurality of support arms flexibly supporting the second seismic mass such that the second seismic mass and second plurality of rotor elements are movably coupled to the central anchor portion.

17. The microelectromechanical structure of claim 6, further comprising:

a second seismic mass separated from the central anchor portion;

a second plurality of stator elements; and

a second plurality of mobile rotor elements interleaved with the second plurality of stator elements, the second plurality of mobile rotor elements extending from and being supported by the second seismic mass, wherein the first plurality of stator elements and the first plurality of mobile rotor elements are positioned between the first seismic mass and the central anchor portion and the second plurality of stator elements and the second plurality of rotor elements are positioned between the second seismic mass and the central anchor portion.

18. The microelectromechanical structure of claim 6 wherein the first plurality of flexible support arms includes first and second support arms, the first support arm extending from a first end of the central anchor portion to a first end of the first seismic masses and the second support arm extending from a second end of the central anchor portion to a second end of the first seismic mass and the rotor further includes:

a second seismic mass separated from the central anchor portion;

a third support extending from the first end of the central anchor portion to a first end of the second seismic mass; and

a fourth support arm extending from the second end of the central anchor portion to a second end of the second seismic mass.

19. The microelectromechanical structure of claim 6, further comprising second, third, and fourth pluralities of stator elements, wherein the first plurality of flexible support arms includes first and second flexible support arms and the rotor further includes:

a second seismic mass separated from the central anchor portion;

a third flexible support arm extending between the second seismic mass and the central anchor portion;

a second plurality of mobile rotor elements interleaved with the second plurality of stator elements, the second plurality of mobile rotor elements extending from the second seismic mass;

a third plurality of mobile rotor elements extending from the first flexible support arm and interleaved with the third plurality of stator elements; and

a fourth plurality of mobile rotor elements extending from the second flexible support arm and interleaved with the fourth plurality of stator elements.