Micromechanical magnetic field sensor

• US 6,215,318 B1
• Filed: 06/18/1999
• Issued: 04/10/2001
• Est. Priority Date: 06/18/1998
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Emmerich, Harald, Schoefthaler, Martin, Schellin, Ralf, Kaienburg, Joerg
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): LEROUX, ETIENNE PIERRE
• Application Number:
  US09/336,628
• Time in Patent Office: 662 Days
• Field of Search: 324/658, 324/207.24, 324/207.21, 324/256, 324/260, 356/429, 356/431, 356/435, 356/73, 257/415, 257/369, 257/414, 257/431, 257/618
• US Class Current: 324/658
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 33/028 Electrodynamic magnetometers
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B

Abstract

A micromechanical magnetic field sensor includes a printed circuit trace device, which is suspended above a substrate and is capable of being deflected elastically. Also included are a first capacitor plate device that is joined to the printed circuit trace device and is able to be deflected together with the printed circuit trace device, and a second, fixed capacitor plate device that is joined to the substrate and forms a capacitor device by interacting with the first capacitor plate device. A magnetic field sensing device conducts a predetermined current through the printed circuit trace device and measures the change in capacitance of the capacitor device arising in dependence on an applied magnetic field. The magnetic field sensing device can also be designed in such a way that it can be calibrated by calibration current loops.

Claims

1. A micromechanical magnetic field sensor, comprising:

a substrate;

a printed circuit trace device suspended above the substrate and being able to be deflected elastically;

a first capacitor plate device joined to the printed circuit trace device and being able to be deflected together with the printed circuit trace device;

a second, fixed capacitor plate device joined to the substrate and forming a capacitor device by interacting with the first capacitor plate device; and

a magnetic field sensing device for conducting a predetermined current through the printed circuit trace device and for measuring a change in a capacitance of the capacitor device arising as a function of an applied magnetic field, and further comprising;

a plurality of spring devices, wherein;

the printed circuit trace device includes a first elongated beam running in a first direction,

the first elongated beam is elastically suspended above the substrate by arranging a first end of the first elongated beam in one of the plurality of spring devices and by arranging a second end of the first elongated beam in another one of the plurality of spring devices, and

the first elongated beam is able to be deflected in a second direction only.

2. The micromechanical magnetic field sensor according to claim 1, wherein:

the printed circuit trace device includes;

a second beam branching from the first elongated beam in a first direction above the substrate, and

a third beam branching from the first elongated beam in a second direction above the substrate and that is opposite to the first direction, and

wherein the second beam and the third beam are associated with a uniform electrical potential of a branching point from the printed circuit trace device.

3. The micromechanical magnetic field sensor according to claim 2, wherein:

the first capacitor plate device includes a plurality of beams branching from the second beam and the third beam and running over the substrate according to an orientation that is one of parallel and vertical with respect to the first elongated beam.

4. The micromechanical magnetic field sensor according to claim 2, wherein:

an electrical potential corresponding to a uniform electrode potential is tapped at an end of at least one of the second beam and the third beam which is distant from an end of the first elongated beam.

5. The micromechanical magnetic field sensor according to claim 1, wherein:

the second capacitor plate device includes a plurality of beams anchored in the substrate at one end thereof and arranged according to a configuration such that the plurality of beams of the second capacitor plate device forms a differential capacitor device with respect to the first capacitor plate device.

6. The micromechanical magnetic field sensor according to claim 1, further comprising:

an arrangement for conducting a direct current through the printed circuit trace device and for sensing the applied magnetic field via a static change in the capacitance.

7. The micromechanical magnetic field sensor according to claim 1, further comprising:

conducting an alternating current through the printed circuit trace device and sensing the applied magnetic field via a dynamic change in the capacitance, and wherein the alternating current having a natural frequency of the printed circuit trace device and the first capacitor plate device.

8. The micromechanical magnetic field sensor according to claim 1, further comprising:

a conductive layer deposited at least on the first elongated beam of the printed circuit trace device, the conductive layer corresponding to one of a doped epitaxial polysilicon layer and an aluminum layer.

9. The micromechanical magnetic field sensor according to claim 1, further comprising:

a calibration current loop provided on the substrate and for impressing a calibrating magnetic field.

10. The micromechanical magnetic field sensor according to claim 1, further comprising:

a third capacitor plate device wherein the third capacitor plate device forms an additional capacitor device with respect to the first capacitor plate device; and

sensing a change in the capacitance of the additional capacitor device arising as a function of the applied magnetic field.

11. The micromechanical magnetic field sensor according to claim 10, further comprising:

a cap provided over the substrate, wherein;

the third capacitor plate device includes a fourth conducting layer located in the substrate and a fifth conducting layer located on the cap.

12. The micromechanical magnetic field sensor according to claim 11, wherein:

the fifth conducting layer is patterned such that the fifth conducting layer is removed from an interconnecting region between the substrate and the cap.

13. A process for manufacturing a micromechanical magnetic field sensor, comprising the steps of:

(a) providing and patterning a first insulating layer on a substrate;

(b) providing and patterning a first conducting layer on the patterned first insulating layer;

(c) providing and patterning a second insulating layer on the patterned first conducting layer;

(d) providing and patterning a second conducting layer on the patterned second insulating layer to form a printed circuit trace device and a capacitor device;

(e) undercutting deflectable components from at least one of the first insulating layer and the second insulating layer, and

(f) forming, electrical connections for the printed circuit trace device and for the capacitor device from the patterned first conducting layer.

14. The process according to claim 13, further comprising the step of:

encapsulating the deflectable components.

15. The process according to claim 13, further comprising the steps of:

providing a cap; and

applying and patterning a further conducting layer on the cap.

16. A micromechanical magnetic field sensor, comprising:

a substrate;

a printed circuit trace device freely suspended above the substrate and being able to be deflected elastically;

a first capacitor plate device extending from the printed circuit trace device and being able to be deflected together with the printed circuit trace device;

a second capacitor plate device on the substrate and forming a capacitor device by interacting with the first capacitor plate device; and

a magnetic field sensing device for conducting a predetermined current through the printed circuit trace device and for measuring a change in a capacitance of the capacitor device arising as a function of an applied magnetic field.

17. The micromechanical magnetic field sensor of claim 16, wherein the second capacitor plate device on the substrate is secured to the substrate at one end.

18. The micromechanical magnetic field sensor of claim 16, wherein the second capacitor plate device on the substrate is fixed to the substrate.