Capacitive sensor and a method for manufacturing the capacitive sensor

• US 7,555,950 B2
• Filed: 09/23/2005
• Issued: 07/07/2009
• Est. Priority Date: 09/23/2004
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: Mutikainen, Risto, Ruohio, Jaakko
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Gissel; Gunnar J
• Application Number:
  US11/232,922
• Publication Number:
  US 20060213269A1
• Time in Patent Office: 1,383 Days
• Field of Search: 735/143.2, 735/140.1, 737/18, 737/24
• US Class Current: 73/514.32
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

The present invention relates to measuring devices for use in physical measuring, and in particular to capacitive sensors. In the sensor according to the invention, the shape of the stationary electrode (3), (4), (12), (17-20), (27-28) is stepped. Through the invention, a method for manufacturing a capacitive sensor with improved linearity is achieved, as well as a capacitive sensor suitable for use particularly in small capacitive sensor solutions.

Claims

1. A capacitive sensor comprising:

a movable electrode; and

a stationary electrode; and

a stationary surface of the capacitive sensor,

wherein the shape of the stationary electrode is stepped,

wherein the stationary electrode is manufactured onto the stationary surface of the capacitive sensor using thin-film technology,

wherein the shape of the stationary surface of the capacitive sensor is essentially planar, and

wherein the capacitive sensor is configured to measure capacitance.

2. The sensor according to claim 1, wherein the shape of the stationary electrode is essentially concave.

3. The sensor according to claim 1, wherein the shape of the stationary electrode is essentially convex.

4. The sensor according to claim 1, wherein the shape of the stationary electrode is essentially the shape of an inclined plane.

5. The sensor according to claim 4, wherein the shape of the stationary electrode is the shape of an inclined plane, which essentially coincides with a rotating plane at an extreme position.

6. The sensor according to claim 1, wherein the shape of the stationary electrode is implemented such, that the electrodes touch at several distinct spots essentially over their entire surface when the movable electrode is at the extreme position.

7. The sensor according to claim 1, wherein the shape of the stationary electrode is optimized such, that a minimum of linearity error is achieved.

8. The sensor according to claim 7, wherein the shape of the stationary electrode is a lower order approximation of the equation for the ideal shape.

9. The sensor according to claim 1, wherein the stationary electrode is manufactured layer by layer out of metal.

10. The sensor according to claim 9, wherein the thicknesses of the metal layers of the stationary electrode are unequal.

11. The sensor according to claim 9 wherein the metal layers of the stationary electrode consist of mutually different metals or alloys.

12. The sensor according to claim 1, wherein the shape of the stationary electrode is essentially circular in a plane.

13. The sensor according to claim 1, wherein the shape of the stationary electrode is essentially quadrangular in a plane.

14. The sensor according to claim 12, wherein the stationary electrode is essentially cylindrically concave or convex.

15. The sensor according to claim 12 wherein the stationary electrode is essentially spherically concave or convex.

16. The sensor according to claim 12 wherein there is a hole in the center of the metal layer of the stationary electrode.

17. The sensor according to claim 1, wherein the structure of the stationary electrode is non-singly monolithic.

18. The sensor according to claim 17, wherein support structures have been added to the stationary electrode.

19. The sensor according to claim 1, wherein the movable electrode is supported by a torsion spring.

20. The sensor according to claim 1, wherein the movable electrode is supported by a bending spring.

21. The sensor according to claim 1, wherein the sensor is a capacitive pressure sensor.

22. The sensor according to claim 1, wherein the sensor is a capacitive acceleration sensor.

23. The sensor according to claim 1, wherein the sensor is a capacitive sensor of angular velocity.

24. A method for manufacturing a stationary electrode of a capacitive sensor, the method comprising:

metallizing a metal layer onto a stationary surface of the capacitive sensor;

patterning the metal layer by removing the metal layer elsewhere than in the area of the desired pattern; and

repeating the metallizing and the patterning at least once such that a stepped electrode structure is obtained,

wherein the stationary electrode of the capacitive sensor is manufactured onto the stationary surface of the capacitive sensor in a stepped fashion using thin-film technology,

wherein the stationary surface of the capacitive sensor is essentially planar, and

wherein the capacitive sensor is configured to measure capacitance.

25. The method according to claim 24, wherein the stationary electrode is manufactured such that an electrode structure of essentially concave shape is obtained.

26. The method according to claim 24, wherein the stationary electrode is manufactured such that an electrode structure of essentially convex shape is obtained.

27. The method according to claim 24, wherein the stationary electrode is manufactured such that an electrode structure of essentially the shape of an inclined plane is obtained.

28. The method according to claim 27, wherein the stationary electrode is manufactured such that an electrode structure shape is obtained being the shape of an inclined plane, which essentially coincides with a rotating plane at an extreme position.

29. The method according to claim 24, wherein the patterning is implemented by etching.

30. The method according to claim 24, wherein the patterning is implemented additively by means of a lift-off technique.

31. The method according to claim 24, wherein the thicknesses of the metal layers of the stationary electrode are unequal.

32. The method according to claim 24, wherein the metal layers of the stationary electrode consist of mutually different metals or alloys.

33. The method according to claim 24, wherein the stationary electrode is manufactured to such a shape, that the stationary electrode and a movable electrode touch at several distinct spots essentially over their entire surface when the movable electrode of the capacitive sensor is at the extreme position.

34. The method according to claim 24, wherein the shape of the stationary electrode is optimized such, that a minimum of linearity error is achieved.

35. The method according to claim 34, wherein shape of the stationary electrode is a lower order approximation of the ideal shape.

36. The method according to claim 24, wherein the stationary electrode is manufactured essentially in the shape of a circle in a plane.

37. The method according to claim 24, wherein the stationary electrode is manufactured essentially in the shape of a quadrangle in a plane.

38. The method according to claim 37, wherein the stationary electrode is manufactured essentially to a cylindrically concave or convex shape.

39. The method according to claim 37 wherein the stationary electrode is manufactured essentially to a spherically concave or convex shape.

40. The method according to claim 38 wherein a hole is made in the stationary electrode at the center of the metal layer.

41. The method according to claim 24, wherein the stationary electrode is manufactured such that its structure is non-singly monolithic.

42. The method according to claim 41, wherein support structures are added to the stationary electrode.

43. The method according to claim 24, wherein a movable electrode of the capacitive sensor is supported by a torsion spring.

44. The method according to claim 24, wherein a movable electrode of the capacitive sensor is supported by a bending spring.

45. The method according to claim 24, wherein the capacitive sensor is made into a capacitive pressure sensor.

46. The method according to claim 24, wherein the capacitive sensor is made into a capacitive acceleration sensor.

47. The method according to claim 24, wherein the capacitive sensor is made into a capacitive sensor of angular velocity.