Magnetic tunnel junction sensor with moveable cladding

• US 20070159735A1
• Filed: 10/19/2006
• Published: 07/12/2007
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Everspin Technologies Incorporated
• Original Assignee: Everspin Technologies Incorporated
• Inventors: Engel, Bradley, Smith, Kenneth, Butcher, Brian
• Granted Patent: US 7,602,177 B2
• Time in Patent Office: Days
• US Class Current: 360/324.200
• CPC Class Codes: G01R 33/06 using galvano-magnetic devices

Abstract

Methods (300, 400) and apparatus (46, 416, 470) are provided for sensing physical parameters. The apparatus (46, 416, 470) comprises a magnetic tunnel junction (MTJ) (32, 432), a magnetic field source (MFS) (34, 445, 476) whose magnetic field (35) overlaps the MTJ (32, 432) and a moveable magnetic cladding element (33, 448, 478) whose proximity (43, 462, 479, 479′) to the MFS (34, 445, 476) varies in response to an input to the sensor. The MFS (34, 445, 476) is located between the cladding element (33, 448, 478) and the MTJ (32, 432). Motion (41, 41′, 41-1, 464, 477) of the cladding element (33, 448, 478) relative to the MFS (34, 445, 476) in response to sensor input causes the magnetic field (35) at the MTJ (32, 432) to change, thereby changing the electrical properties of the MTJ (32, 432). A one-to-one correspondence (54) between the sensor input and the electrical properties of the MTJ (32, 432) is obtained.

Claims

1. A sensor, comprising:

a magnetic tunnel junction (MTJ);

a magnetic field source (MFS) coupled to the MTJ and adapted to provide a magnetic field thereto; and

a magnetic cladding element moveably coupled to the MFS so that when perturbed by an input to the sensor, movement of the cladding element causes the magnetic field at the MTJ provided by the MFS to vary in response to the input to the sensor.

2. The sensor of claim 1, wherein the MFS is fixedly coupled to the MTJ.

3. The sensor of claim 1, wherein the MFS comprises auxiliary cladding elements on lateral sides thereof and the magnetic cladding element has a lateral width relative to the MFS to overlap the combination of the MFS and the auxiliary cladding elements.

4. The sensor of claim 1, wherein the magnetic cladding element has extensions at some lateral edges thereof adapted to engage lateral edges of the MFS as the cladding element approaches the MFS.

5. The sensor of claim 1, further comprising a write-line magnetically coupled to the MTJ on an opposite side of the MTJ from the MFS.

6. The sensor of claim 5, wherein the write-line has further auxiliary magnetic cladding on three sides not facing the MTJ.

7. The sensor of claim 1, further comprising a deflectable element supporting the magnetic cladding and coupled to the sensor input.

8. A sensor comprising:

a magnetic tunnel junction (MTJ) comprising;

a first magnetic electrode;

a second magnetic electrode; and

a dielectric separating the first and second electrodes, adapted to provide tunneling conduction therebetween;

a magnetic field source (MFS) for providing a magnetic field, fixedly located in proximity to the second magnetic electrode; and

magnetic cladding moveably suspended in variable proximity to the MFS so that variation of the proximity of the magnetic cladding to the MFS in response to an input of the sensor causes the magnetic field of the MFS at the MTJ to vary, thereby altering the electrical properties of the MTJ.

9. The sensor of claim 8, wherein the MFS comprises a current carrying conductor.

10. The sensor of claim 9, wherein the current carrying conductor is U-shaped.

11. The sensor of claim 8, wherein the MFS comprises a permanent magnet.

12. The sensor of claim 8, further comprising, a deflectable member for moveably supporting the magnetic cladding in variable proximity to the MFS.

13. The sensor of claim 12, wherein the magnetic cladding is located between the deflectable member and the MFS.

14. The sensor of claim 12, wherein the deflectable member comprises tantalum, tantalum oxide, tantalum nitride, silicon, silicon oxide, silicon oxy-nitride, silicon nitride and/or a combination thereof.

15. The sensor of claim 8, further comprising:

a conductive write-line fixedly located spaced apart from a first side of the MTJ; and

wherein the MFS is fixedly located spaced apart from a second, opposite, side of the MTJ; and

wherein the magnetic cladding is moveably located spaced apart from a side of the MFS not facing the MTJ.

16. A method for forming a sensor, comprising:

providing a magnetic tunnel junction (MTJ);

providing a magnetic field source (MFS) having a first side coupled to the MTJ; and

forming a magnetic cladding, moveably coupled to the MFS on a second, opposite side of the MFS, and adapted to move relative to the MFS in response to input to the sensor, thereby altering the magnetic field provided by the MFS at the MTJ.

17. The method of claim 16, wherein the forming step further comprises:

adding a spacer over the MFS;

forming the magnetic cladding on the spacer; and

removing a portion of the spacer lying between the magnetic cladding and the MFS so that at least a part of the magnetic cladding can move relative to the MFS in response to the sensor input.

18. The method of claim 16, wherein the step of providing the MFS further comprises providing second magnetic cladding on lateral sides of the MFS, wherein the moveable cladding responsive to the sensor input has sufficient lateral width to at least overlap the lateral width of the MFS plus the second cladding.

19. The method of claim 16, wherein the step of forming the magnetic cladding moveably coupled to the MFS, further comprises, bonding a substantially non-magnetic material to the magnetic cladding.

20. The method of claim 16, wherein the substantially non-magnetic material comprises, tantalum, tantalum oxide, tantalum nitride, silicon, silicon oxide, silicon oxy-nitride, silicon nitride and/or a combination thereof.