Micromachined magnetic field sensors
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.
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.