Magnetic tunnel junction pressure sensors and methods

• US 7,547,480 B2
• Filed: 10/28/2005
• Issued: 06/16/2009
• Est. Priority Date: 10/28/2005
• Status: Expired due to Fees

• Current Assignee: Everspin Technologies Incorporated
• Original Assignee: Everspin Technologies Incorporated
• Inventors: Baird, Robert W., Engel, Bradley N., Chung, Young Sir
• Primary Examiner(s): Bernatz; Kevin M
• Application Number:
  US11/262,064
• Publication Number:
  US 20070099031A1
• Time in Patent Office: 1,327 Days
• Field of Search: None
• US Class Current: 428/811.1
• CPC Class Codes: G01L 19/16 Dials; Mounting of dials
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1143 with defined structural feature
• CPC Class Codes: Y10T 428/1171 with defined laminate structural detail

Abstract

An integrated circuit device is provided which comprises a substrate, a conductive line configured to experience a pressure, and a magnetic tunnel junction (“MTJ”) core formed between the substrate and the current line. The conductive line is configured to move in response to the pressure, and carries a current which generates a magnetic field. The MTJ core has a resistance value which varies based on the magnetic field. The resistance of the MTJ core therefore varies with respect to changes in the pressure. The MTJ core is configured to produce an electrical output signal which varies as a function of the pressure.

Claims

1. An integrated circuit device, comprising:

a substrate;

a first insulating layer having a magnetic tunnel junction (“

MTJ”

) core formed therein;

a second insulating layer, disposed over the first insulating layer, the second insulating layer having a conductive line disposed therein and defining a cavity therein, wherein the conductive line is configured to carry a first current that produces a first magnetic field, and wherein at least a portion of the cavity is disposed directly between the conductive line and the MTJ core and wherein a resistance value of the MTJ core varies with changes in the first magnetic field experienced by the MTJ core.

2. An integrated circuit device according to claim 1, wherein the second insulating layer flexes in response to pressure applied to the second insulating layer and wherein the resistance value of the MTJ core changes in response to pressure experienced by the second insulating layer.

3. An integrated circuit device according to claim 2, wherein a distance between the conductive line and the MTJ core varies based on the pressure experienced by the second insulating layer, and wherein the resistance value of the MTJ core varies with respect to the distance between the conductive line and the MTJ core.

4. An integrated circuit device according to claim 3, wherein the MTJ core is configured to sense the pressure and generate an electrical output signal responsive to the pressure.

5. An integrated circuit device according to claim 4, wherein the electrical output signal generated by the MTJ core varies based on the resistance value of the MTJ core.

6. An integrated circuit device according to claim 5, wherein the electrical output signal of the MTJ core is used to determine the pressure experienced by the second insulating layer.

7. An integrated circuit device according to claim 6, further comprising:

a pressure sensor conversion circuit configured to associate the electrical output signal produced by the MTJ core with the pressure experienced by the second insulating layer.

8. An integrated circuit device according to claim 1, wherein the substrate is formed from front end layers by a front end fabrication process, wherein the MTJ core is formed from back end layers by a back end fabrication process which occurs after the front end fabrication process.

9. An integrated circuit device, comprising:

an insulating layer having;

a conductive line configured to carry a first current that generates a first magnetic field, wherein the conductive line moves in response to change in a pressure experienced by the conductive line;

a magnetic tunnel junction (“

MTJ”

) core having a resistance value which varies as a function of the first magnetic field experienced by the MTJ core, and being configured to generate an electrical output signal which varies based on the resistance value of the MTJ core;

wherein the insulating layer defines a cavity and at least a portion of the cavity is disposed directly between said conductive line and said MTJ core; and

a pressure sensor circuit configured to associate a value of the electrical output signal produced by the MTJ core with a pressure value experienced by the conductive line.

10. A pressure sensor apparatus, comprising:

a substrate;

a first insulating layer formed overlying the substrate;

a magnetic tunnel junction (MTJ) core formed in the first insulating layer;

a second insulating layer comprising;

a deformable diaphragm that is designed to move in response to pressure applied thereto, and a cavity defined in the second insulating layer, wherein the MTJ core is disposed below the cavity; and

a programming bit line at least partially embedded in the deformable diaphragm and suspended over a portion of the cavity, wherein at least a portion of the cavity is disposed directly between the programming bit line and the MTJ core and wherein the programming bit line carries a first current that generates a first magnetic field,

wherein the deformable diaphragm moves in response to pressure applied thereto such that a vertical distance between the programming bit line and the MTJ core changes with changes in the pressure applied to deformable diaphragm which changes the first magnetic field experienced by the MTJ core.

11. A pressure sensor apparatus according to claim 10, wherein the MTJ core generates an output current that varies based on changes in the output tunneling magnetic resistance (TMR) of the MTJ core, and wherein the output tunneling magnetic resistance (TMR) of MTJ core varies with changes in the pressure depending on the vertical distance between MTJ core and programming bit line, and wherein the output current generated by the MTJ core correlates to the pressure applied to the deformable diaphragm.

12. A pressure sensor apparatus according to claim 10, wherein the programming bit line is suspended over the cavity by the deformable diaphragm.

13. A pressure sensor apparatus according to claim 10, wherein the MTJ core comprises:

a ferromagnetic free layer in which a first magnetization orientation is rotatable such that the first magnetization orientation is designed to change in both magnitude and direction;

a ferromagnetic pinned layer in which a second magnetization orientation is fixed in one direction such that a mutual angle of the first magnetization orientation is rotatable with respect to the second magnetization orientation of the pinned layer, and

wherein changes in a first magnetic field experienced by the MTJ core changes the mutual angle between the ferromagnetic pinned layer and the ferromagnetic free layer of the MTJ core, and wherein changes in the mutual angle change the output tunneling magnetic resistance (TMR) of the MTJ core such that an output current of the MTJ core varies with changes in pressure;

a tunnel barrier layer disposed between the ferromagnetic free layer and the ferromagnetic pinned layer, wherein the tunnel baffler layer tunnels an output current from the pinned layer to the free layer;

a first electrode layer below the pinned layer; and

a second electrode layer above the free layer.

14. A pressure sensor apparatus according to claim 13, wherein changes in a relative position of the programming bit line with respect to the MTJ core changes the mutual angle between the free layer and the pinned layer which changes the output TMR of the MTJ core, wherein the first and second magnetizations are oriented in the same direction during a parallel state and in opposite directions during an anti-parallel state.

15. A pressure sensor apparatus according to claim 14, wherein the mutual angle between the ferromagnetic free layer and the ferromagnetic pinned layer is approximately 0°

during the parallel state to result in a low output tunneling magnetic resistance (TMR) of the MTJ core, and wherein the mutual angle between the ferromagnetic free layer and the ferromagnetic pinned layer is approximately 180°

during the anti-parallel state to result in a high output tunneling magnetic resistance (TMR) of the MTJ core.

16. A pressure sensor apparatus according to claim 10, wherein the pressure sensor apparatus comprises a plurality of front end layers further comprising:

an active circuit embedded in the substrate;

a third insulating layer overlying the active circuit, wherein the second insulating layer overlies the third insulating layer; and

a programming digit line that carries a second current that generates a second magnetic field that is sensed by the MTJ core, wherein the programming digit line is embedded in the third insulating layer and wherein the second magnetic field experienced by the MTJ core is dependent upon the second current running through the programming bit line.

17. A pressure sensor apparatus according to claim 16, wherein the active circuit comprises:

an analog active circuit component.

18. A pressure sensor apparatus according to claim 10, further comprising:

a pressure sensor conversion circuit that measures the output current, determines a corresponding output TMR of the MTJ core, and associates the corresponding output TMR with a corresponding sensed pressure value indicative of the pressure experienced by the deformable diaphragm.

19. A pressure sensor apparatus according to claim 18, further comprising:

a processor that uses the corresponding sensed pressure value to control operation of the active circuit.

20. A pressure sensor apparatus according to claim 10, further comprising:

a magnetic shielding layer disposed above the deformable diaphragm to protect an output current generated by the MTJ core from external noise generated by sources adjacent the MTJ core that produce magnetic fields.