Micromachined magnetic field sensors

• US 8,395,381 B2
• Filed: 07/09/2010
• Issued: 03/12/2013
• 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
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US12/833,390
• Publication Number:
  US 20120007598A1
• Time in Patent Office: 977 Days
• Field of Search: 324/249, 324251-252
• US Class Current: 324/249
• 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:

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

at least one electrical wiring layer connecting at least one of the at least two magnetic field sensing elements to a source or a sensing terminal,

wherein the sloped sidewalls are formed by displacing the at least two magnetic field sensing elements vertically with at least one pole.

2. The sensor of claim 1, further comprising a cover layer with at least one cavity, wherein a portion of the sloped sidewalls reside in the at least one cavity.

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

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

5. The sensor of claim 1, wherein at least one CMOS circuitry is formed on a base layer.

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

7. The sensor of claim 5, where the at least two magnetic field sensing terminals are connected to the base layer via bonding agents.

8. The sensor of claim 7 wherein the bonding agents are wirebonds and metal bonding pads.

9. The sensor of claim 7 wherein the bonding agents are interconnect layers for wafer level bonding.

10. The sensor of claim 9 wherein bonding agents are patterned thin films of germanium layer, which is bonded to the at least one patterned aluminum layer on the base layer.

11. The sensor of claim 1 wherein the at least two magnetic field sensing elements are Hall effect magnetic sensors.

12. The sensor of claim 11, wherein the at least one magnetic field sensing element comprises N type doped silicon material.

13. The sensor of claim 11, wherein the at least one magnetic field sensing element comprises P type doped silicon material.

14. The sensor of claim 1 wherein the at least two magnetic field sensing elements are 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.

15. The sensor of claim 1, further comprising at least one bump, the at least one bump rests on the at least one pole to form the sloped sidewalls.