Sensor and method for detecting a deformation

• US 20060097720A1
• Filed: 07/05/2005
• Published: 05/11/2006
• Est. Priority Date: 07/05/2004
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Zimmer, Juergen, Schmitt, Stephan
• Granted Patent: US 7,319,322 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: G01L 1/125 by using magnetostrictive means magnetostrictive sensors H10N35/101
• CPC Class Codes: G01L 9/007 using variations in inductance
• CPC Class Codes: G01P 15/105 by magnetically sensitive devices

Abstract

A sensor has a substrate having a mechanically deformable region, a magnetostrictive spin-valve sensor element being arranged to detect a mechanical deformation of the mechanically deformable region. On the substrate, there is a device for generating a controllable magnetic field by which a performance of the sensor element is influenced.

Claims

1. A sensor comprising:

a substrate having a mechanically deformable region;

a magnetostrictive multi-layer sensor element for detecting a mechanical deformation of the mechanically deformable region, the multi-layer sensor element comprising a sensor layer consisting of a material having a positive or a negative magnetostriction constant; and

a device, arranged on the substrate, for generating a controllable magnetic field by which a performance of the sensor element is influenced.

2. A sensor according to claim 1, wherein the multi-layer sensor element comprises a magnetic layer system comprising at least two magnetic layers and a non-magnetic layer, the magnetic layer system being formed such that the magnetization directions of at least two neighboring magnetic layers change when extended.

3. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is a GMR sensor element or a TMR sensor element.

4. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is a magnetostrictive spin-valve sensor element.

5. A sensor according to claim 1, wherein the device for generating a controllable magnetic field is integrated in the substrate.

6. A sensor according to claim 5, wherein the device for generating a controllable magnetic field includes a conductor structure.

7. A sensor according to claim 6, wherein the conductor structure includes a straight longitudinal region extending over the magnetostrictive multi-layer sensor element.

8. A sensor according to claim 1, wherein the mechanically deformable region is a bending beam or a membrane.

9. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element and the device for generating a controllable magnetic field is formed to rotate a magnetization direction of a magnetically soft layer of the spin-valve sensor element, thereby influencing the electrical resistance of the spin-valve sensor element.

10. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element and the device for generating a controllable magnetic field are arranged such that the magnetic field has a component in the extension direction of the mechanically deformable region at the position of the magnetostrictive multi-layer sensor element.

11. A sensor according to claim 10, wherein the magnetostrictive multi-layer sensor element and the device for generating a controllable magnetic field are arranged such that the magnetic field generated and the extension direction of the mechanically deformable region at the position of the magnetostrictive multi-layer sensor element are parallel to each other.

12. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element and the device for generating a controllable magnetic field are arranged such that the magnetic field generated is perpendicular to the extension direction of the mechanically deformable region at the position of the magnetostrictive multi-layer sensor element.

13. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element, wherein a magnetization of a magnetically hard layer of the spin-valve sensor element and a magnetization of the magnetically soft layer of the spin-valve sensor element, without a magnetic field applied and without a mechanical deformation of the mechanically deformable region, are parallel or anti-parallel to each other.

14. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element, wherein a magnetization of the magnetically hard layer and a magnetization of the magnetically soft layer of the spin-valve sensor element, without a magnetic field applied and without a mechanical deformation of the mechanically deformable region, comprise an angle between 0°

and 180°

.

15. A sensor according to claim 14, wherein the spin-valve sensor element is formed so that the magnetization of the magnetically hard layer and the magnetization of the magnetically soft layer, without a magnetic field applied and without a mechanical deformation of the mechanically deformable region, are perpendicular to each other.

16. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element arranged such that a magnetization of the magnetically hard layer is parallel to an extension of the mechanically deformable region at the position of the spin-valve sensor element.

17. A sensor according to claim 1, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element arranged such that a magnetization of the magnetically hard layer and an extension direction of the mechanically deformable region at the position of the spin-valve sensor element comprise an angle of ±

45°

or ±

135°

.

18. A sensor according to claim 1, wherein another magnetostrictive multi-layer sensor element is arranged in addition to a magnetostrictive multi-layer sensor element.

19. A sensor according to claim 18, wherein the one magnetostrictive multi-layer sensor element and the other magnetostrictive multi-layer sensor element are connected to form a half-bridge, the other magnetostrictive multi-layer sensor element being arranged such that an extension of the mechanically deformable region at the position of the other magnetostrictive multi-layer sensor element does not influence the magnetization direction of the soft magnetic layer.

20. A sensor according to claim 18, wherein the other magnetostrictive spin-valve sensor element is arranged such that a magnetization of the magnetically hard layer is perpendicular to an extension direction of the mechanically deformable region at the position of the other magnetostrictive spin-valve sensor element.

21. A sensor according to claim 18, wherein the other magnetostrictive spin-valve sensor element is arranged such that an angle between a magnetization of the magnetically hard layer and an extension direction of the mechanically deformable region at the position of the other magnetostrictive spin-valve sensor element has a value of ±

45°

.

22. A sensor according to claim 1, wherein the device for generating a controllable magnetic field is connected to a controller.

23. A sensor according to claim 22, wherein the controller is formed to control the device for generating a controllable magnetic field when a predetermined value of a linearity or a sensitivity of the output characteristic curve of the sensor element is fallen below or exceeded by a predetermined magnitude such that a magnetic field differing from the previous magnetic field is generated by it.

24. A sensor according to claim 22, wherein the controller is formed to keep a resistance of the sensor element constant independently of a deformation of the mechanically deformable region.

25. A method for detecting a deformation of a mechanically deformable region arranged on a substrate by means of a magnetostrictive multi-layer sensor element, comprising the steps of:

adjusting an operating point of the magnetostrictive multi-layer sensor element by applying a magnetic field; and

detecting a value indicating the mechanical deformation of the mechanically deformable region at the position of the magnetostrictive multi-layer sensor element.

26. A method according to claim 25, wherein the step of adjusting an operating point takes place in dependence on a linearity of the characteristic curve of the magnetostrictive multi-layer sensor element.

27. A method according to claim 26, wherein the step of adjusting an operating point comprises the steps of:

determining a linearity of the characteristic curve of the magnetostrictive multi-layer sensor element at an operating point adjusted;

comparing the linearity of the characteristic curve to a predetermined value; and

generating a new magnetic field differing from the previous magnetic field when the linearity of the characteristic curve at the previous operating point differs from a predetermined value by a predetermined magnitude.

28. A method according to claim 27, wherein the step of determining a linearity takes place by means of one or several reference characteristic curves of the magnetostrictive multi-layer sensor element.

29. A method according to claim 25, wherein the step of adjusting an operating point takes place in dependence on a sensitivity of the sensor element.

30. A method according to claim 29, wherein the step of adjusting an operating point comprises the steps of:

determining a sensitivity of the magnetostrictive multi-layer sensor element at an operating point adjusted;

comparing the sensitivity to a predetermined value; and

generating a new magnetic field differing from the previous magnetic field when the sensitivity at the previous operating point differs from a predetermined value by a predetermined magnitude.

31. A method according to claim 25, wherein the magnetic field is adjusted in dependence on one or several parameters causing a drift of the magnetostrictive multi-layer sensor element.

32. A method according to claim 25, wherein the operating point is adjusted such that an electrical resistance of the magnetostrictive multi-layer sensor element is kept constant independently of a deformation of the mechanically deformable region.

33. A method according to claim 32, wherein the magnetostrictive multi-layer sensor element is formed as a spin-valve sensor element, the electrical resistance of the spin-valve sensor element being obtained by keeping the direction of the magnetically soft layer at a predetermined value.

34. A method according to claim 32, wherein the step of detecting a value of a mechanical deformation comprises detecting a value indicating a value of the magnetic field generated.

35. A method according to claim 34, wherein the value detected is a value of the electrical current generating the magnetic field.

36. A method according to claim 25, wherein in the step of adjusting an operating point, the magnetic field is generated depending on an offset value of the multi-layer sensor element.

37. A method according to claim 25, wherein the magnetic field is generated by a device integrated on the substrate.