Magnetoresistance sensor with reduced side reading, and its fabrication

• US 20030193761A1
• Filed: 04/12/2002
• Published: 10/16/2003
• Est. Priority Date: 04/12/2002
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Cornwell, Dwight Jr., Pinarbasi, Mustafa, Gill, Hardayal Singh
• Granted Patent: US 6,785,103 B2
• Time in Patent Office: Days
• US Class Current: 360/324.12
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/3932 Magnetic biasing films

Abstract

A magnetoresistance sensor includes a substrate and a sensor structure deposited upon the substrate and having a first lateral side and a second lateral side. The sensor structure includes a layered transverse biasing structure, a free layer deposited upon the layered transverse biasing structure, and a cap layer deposited upon a central portion of the free layer but not upon a side portion of the free layer adjacent to each lateral side. Longitudinal hard biasing structures are disposed laterally adjacent to the lateral sides of the sensor structure. Each longitudinal hard biasing structure has a magnetic seed layer deposited upon the substrate, the respective lateral side of the sensor structure, and the respective side portion of the free layer. A magnetic hard bias layer is deposited upon the seed layer.

Claims

1. A magnetoresistance sensor comprising:

a substrate;

a sensor structure overlying the substrate and having a lateral side, the sensor structure comprising

a layered transverse biasing structure, and

a free layer contacting the layered transverse biasing structure, the free layer having

a central portion that is magnetically free to respond to an external magnetic field, and

a side portion extending toward the central portion from the lateral side and which is magnetically pinned so that it is not free to respond to the external magnetic field; and

a longitudinal hard biasing structure contacting at least the lateral side of the sensor structure.

2. The magnetoresistance sensor of claim 1, wherein the side portion of the free layer is pinned by exchange coupling from the longitudinal hard biasing structure.

3. The magnetoresistance sensor of claim 1, wherein the side portion of the free layer has a width exceeding about 0.05 micrometers.

4. The magnetoresistance sensor of claim 1, wherein the longitudinal hard biasing structure comprises

a magnetic hard bias layer overlying the lateral side of the sensor structure and the side portion of the free layer contacting the seed layer.

5. The magnetoresistance sensor of claim 1, wherein the longitudinal hard biasing structure comprises

a seed layer contacting the substrate, the lateral side of the sensor structure, and the side portion of the free layer, the seed layer having a seed layer crystal structure and being a magnetic material, and

a magnetic hard bias layer contacting the seed layer, the hard bias layer having a hard bias layer crystal structure.

6. The magnetoresistance sensor of claim 5, wherein the seed layer crystal structure is body centered cubic, and the hard bias layer crystal structure is hexagonal close packed.

7. The magnetoresistance sensor of claim 1, wherein the sensor structure comprises a giant magnetoresistance sensor.

8. The magnetoresistance sensor of claim 1, wherein the sensor structure further includes

a cap layer overlying at least a portion of the free layer;

and

9. A magnetoresistance sensor comprising:

a substrate;

a sensor structure deposited upon the substrate and having a first lateral side and a second lateral side, the sensor structure comprising

a layered transverse biasing structure,

a free layer contacting the layered transverse biasing structure, and

a cap layer deposited upon a central portion of the free layer but not upon a side portion of the free layer adjacent to each lateral side thereof; and

a first longitudinal hard biasing structure laterally adjacent to the first lateral side of the sensor structure and a second longitudinal hard biasing structure laterally adjacent to the second lateral side of the sensor structure, each longitudinal hard biasing structure comprising

a seed layer deposited upon the substrate, each lateral side of the sensor structure, and each side portion of the free layer, the seed layer having a seed layer crystal structure and being a magnetic material, and

a magnetic hard bias layer deposited upon the seed layer, the hard bias layer having a hard bias layer crystal structure.

10. The magnetoresistance sensor of claim 9, wherein the side portion of the free layer has a width exceeding about 0.05 micrometers.

11. The magnetoresistance sensor of claim 9, wherein the sensor structure comprises a giant magnetoresistance sensor.

12. The magnetoresistance sensor of claim 9, wherein the hard bias layer physically contacts at least a portion of the cap layer.

13. The magnetoresistance sensor of claim 9, wherein the seed layer crystal structure is body centered cubic, and the hard bias layer crystal structure is hexagonal close packed.

14. The magnetoresistance sensor of claim 9, wherein the seed layer is a CoFeCr alloy, and the hard bias layer is a CoPtCr alloy.

15. A method of fabricating a magnetoresistance sensor comprising the steps of

providing a substrate;

depositing a sensor structure upon the substrate, the sensor structure having a lateral side and comprising

a layered transverse biasing structure, and

a free layer in contact with the layered transverse biasing structure, the free layer having a central portion and a side portion adjacent to the lateral side;

depositing a longitudinal hard biasing structure contacting the sensor structure by the step of

depositing a magnetic hard bias layer overlying the lateral side of the sensor structure and the side portion of the free layer but not the central portion of the free layer, the hard bias layer having a hard bias layer crystal structure.

16. The method of claim 15, wherein the step of depositing a sensor structure includes the steps of

depositing a cap layer overlying the entire free layer, and

removing a portion of the cap layer to expose the side portion of the free layer adjacent to the lateral side.

17. The method of claim 15, wherein the step of depositing the free layer includes the step of

depositing the free layer such that the side portion of the free layer exceeds about 0.05 micrometers in width.

18. The method of claim 15, wherein the step of depositing a sensor structure comprises the step of

depositing a giant magnetoresistance structure.

19. The method of claim 15, wherein the step of depositing the longitudinal hard biasing structure includes an additional step, prior to the step of depositing the magnetic hard bias layer, of

depositing a magnetic seed layer upon the lateral side of the sensor structure and the side portion of the free layer but not the central portion of the free layer, the seed layer having a seed layer crystal structure, and

wherein the step of depositing the magnetic hard bias layer includes the step of

depositing the magnetic hard bias layer in contact with the magnetic seed layer.