MICROMACHINED MAGNETIC FIELD SENSORS

• US 20120007598A1
• Filed: 07/09/2010
• Published: 01/12/2012
• Est. Priority Date: 07/09/2010
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Lo, Chiung C., Seeger, Joseph, Lim, Martin
• Granted Patent: US 8,395,381 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: G01R 33/0011 comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A micromachined magnetic field sensor integrated with electronics is disclosed. The magnetic field sensors utilize Hall-effect sensing mechanisms to achieve 3-axis sensing. A Z axis sensor can be fabricated either on a device layer or on a conventional IC substrate with the design of conventional horizontal Hall plates. An X and Y axis sensor are constructed on the device layer. In some embodiments, a magnetic flux concentrator is applied to enhance the performance of the magnetic field sensor. In some embodiments, the magnetic field sensors are placed on slope sidewalls to achieve 3-axis magnetic sensing system. In some embodiments, a stress isolation structure is incorporated to lower the sensor offset. The conventional IC substrate and device layer are connected electrically to form a 3-axis magnetic sensing system. The magnetic field sensor can also be integrated with motion sensors that are constructed in the similar technology.

Claims

1. A micromachined magnetic field sensor comprises:

a layer comprising;

at least two magnetic field sensing elements formed only on the slope sidewall areas, such that the outputs of the at least two elements are combined to detect the in-plane magnetic fields and out of plane magnetic fields; and

at least one electrical wiring layer connecting the at least one magnetic field sensing element to a source or a sensing terminal.

2. The sensor of claim 1, wherein the slope sidewalls are formed in at least one micromachined cavity within the layer.

3. The sensor of claim 2, wherein the cavity is formed by micromachining reactive ion etching.

4. The sensor of claim 2, wherein the cavity is formed by micromachining wet etching.

5. The sensor of claim 2, wherein the cavity is formed by wafer saw.

6. The sensor of claim 1, wherein at least one CMOS circuitry is formed on the layer.

7. The sensor of claim 1, wherein the at least one magnetic field sensing element comprises III-V compound material.

8. The sensor of claim 1, where the terminals are connected to a conventional IC substrate comprising signal processing circuitry via bonding agents.

9. The sensor of claim 8 wherein the bonding agents are wirebonds and metal bonding pads.

10. The sensor of claim 8 wherein the bonding agents are interconnect layers for wafer level bonding.

11. The sensor of claim 10 wherein bonding agents are patterned thin films of germanium layer, which is bonded to the at least one patterned aluminum layer on the conventional IC substrate.

12. The sensor of claim 8 further comprising a magnetic sensing element on the conventional IC substrate.

13. The sensor of claim 1 further comprising a cover substrate to protect the micromachined magnetic field sensor from damages and interferences.

14. The sensor of claim 1 comprises a Hall effect magnetic sensor.

15. The sensor of claim 14, wherein the slope sidewalls are formed by displacing the magnetic field sensing elements vertically with at least one pole during micromachining process.

16. The sensor of claim 14, wherein the at least one magnetic field sensing element comprises N type doped silicon material.

17. The sensor of claim 14, wherein the at least one magnetic field sensing element comprises P type doped silicon material.

18. The sensor of claim 1 comprises any of a Lorentz effect magnetic sensor;

a magnetoresistive sensor;

a magneto-diode sensor;

a magneto-transistor;

a fluxgate;

a magneto-impedance sensor;

a magneto-optical sensor; and

MAGFET.

27. The method of claim 8 wherein the bonding agents are wirebonds and metal bonding pads.

32. The method of claim 14, wherein the slope sidewalls are formed by displacing the magnetic field sensing elements vertically with at least one pole during micromachining process.

33. The method of claim 14, wherein the at least one magnetic field sensing element comprises N type doped silicon material.

34. The method of claim 14, wherein the at least one magnetic field sensing element comprises P type doped silicon material.

35. The method of claim 1 comprises any of a Lorentz effect magnetic sensor;

a magnetoresistive sensor;

a magneto-diode sensor;

a magneto-transistor;

a fluxgate;

a magneto-impedance sensor;

a magneto-optical sensor; and

MAGFET.

19. A method for providing a magnetic field sensor comprises:

providing a layer comprising;

providing at least two magnetic field sensing elements formed only on the slope sidewall areas, such that the outputs of the at least two elements are combined to detect the in-planee magnetic fields and out of plane magnetic fields; and

at least one electrical wiring layer connecting the at least one magnetic field sensing element to a source or a sensing terminal.

20. The method of claim 19, wherein the slope sidewalls are formed in at least one micromachined cavity within the layer.

21. The method of claim 20, wherein the cavity is formed by micromachining reactive ion etching.

22. The method of claim 20, wherein the cavity is formed by micromachining wet etching.

23. The method of claim 20, wherein the cavity is formed by wafer saw.

24. The method of claim 19, wherein at least one CMOS circuitry is formed on the layer.

25. The method of claim 19, wherein the at least one magnetic field sensing element comprises III-V compound material.

26. The method of claim 19, where the terminals are connected to a conventional IC substrate comprising signal processing circuitry via bonding agents.

28. The method of claim 26 wherein the bonding agents are interconnect layers for wafer level bonding.

29. The method of claim 28 wherein bonding agents are patterned thin films of germanium layer, which is bonded to the at least one patterned aluminum layer on the conventional IC substrate.

30. The method of claim 26 further comprising a magnetic sensing element on the conventional IC substrate.

31. The method of claim 19 further comprising a cover substrate to protect the micromachined magnetic field sensor from damages and interferences.