Magnetic element with improved field response and fabricating method thereof

• US 6,376,260 B1
• Filed: 04/05/2001
• Issued: 04/23/2002
• Est. Priority Date: 07/19/1999
• Status: Expired due to Term

• Current Assignee: Everspin Technologies Incorporated
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Shi, Jing, Slaughter, Jon Michael, Chen, Eugene Youjun
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): KIELIN, ERIK J
• Application Number:
  US09/825,705
• Time in Patent Office: 383 Days
• Field of Search: 438/3, 365/171, 365/173, 365/158
• US Class Current: 438/3
• 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: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01F 10/3268 the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
• CPC Class Codes: H01F 10/3272 by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

An improved and novel fabrication method for a magnetic element, and more particularly a magnetic element (10) including a first electrode (14) , a second electrode (18) and a spacer layer (16). The first electrode (14) includes a fixed ferromagnetic layer (26) having a thickness t₁. A second electrode (18) is included and comprises a free ferromagnetic layer (28) having a thickness t₂. A spacer layer (16) is located between the fixed ferromagnetic layer (26) and the free ferromagnetic (28) layer, the spacer layer (16) having a thickness t₃, where 0.25t₃<t₁<2t₃, thereby producing near zero magnetic field at the free ferromagnetic layer (28).

Claims

1. A method of fabricating a magnetic element comprising the steps of:

providing a substrate element having a surface;

forming a first electrode on the substrate, the first electrode comprising a fixed ferromagnetic layer whose magnetization is fixed in a preferred direction in the presence of an applied magnetic field, the fixed ferromagnetic layer having a top surface, a bottom surface and a thickness t₁;

forming a spacer layer on the fixed ferromagnetic layer of the first electrode, the spacer layer having a thickness t₃; and

forming a second electrode on the spacer layer comprising a free ferromagnetic layer whose magnetization is free to rotate in the presence of an applied magnetic field, the free ferromagnetic layer having a thickness t₂;

wherein t₁ is chosen such that the magnetic fields produced by the topology of the top surface and the bottom surface of the fixed ferromagnetic layer cancel to produce near zero coupling energy between the free ferromagnetic layer and the fixed ferromagnetic layer.

2. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a first electrode comprising a fixed ferromagnetic layer includes the step of adjusting the roughness of an interface of the fixed ferromagnetic layer, thereby providing for near zero coupling.

3. A method of fabricating a magnetic element as claimed in claim 2, wherein the step of adjusting the roughness of an interface of the fixed ferromagnetic layer includes one of ion bombardment, adjusting the thickness of the fixed ferromagnetic layer and deposition of a third material on a surface of the fixed ferromagnetic layer.

4. A method of fabricating a magnetic element as claimed in claim 1 wherein t₁ is chosen in the range 0.25t₃<

t₁<

2t₃ such that the magnetic fields produced by the topology of the surfaces of the fixed ferromagnetic layer cancel to produce the lowest coupling energy possible between the free ferromagnetic layer and the fixed ferromagnetic layer without degradation of the electrical properties of the device.

5. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a first electrode on the substrate includes forming a first electrode further comprising a pinned ferromagnetic layer and an antiferromagnetic pinning layer exchange coupled thereto, the pinned ferromagnetic layer and the antiferromagnetic pinning layer formed between the substrate and the fixed ferromagnetic layer, the pinned ferromagnetic layer having its magnetization fixed by antiferromagnetic exchange through a spacer layer, in a direction opposite the fixed ferromagnetic layer and thereby defining a SAF structure.

6. A method of fabricating a magnetic element as claimed in claim 1 wherein the steps of forming a first electrode on the substrate and a second electrode on the spacer layer includes forming the fixed ferromagnetic layer and the free ferromagnetic layer to have magnetization directions one of parallel or antiparallel to one another and in the absence of an applied magnetic field.

7. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a first electrode on the substrate and a second electrode on the spacer layer includes forming the free ferromagnetic layer and the fixed ferromagnetic layer to include at least one of NiFe, NiFeCo, CoFe, or Co.

8. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a spacer layer includes forming the spacer layer to include one of a dielectric material defining a MTJ structure or a conductive material defining a spin valve structure.

9. A method of fabricating a magnetic element as claimed in claim 1 further including the step of forming a high moment material located at an interface of the fixed ferromagnetic layer and the spacer layer.

10. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a first electrode on the substrate includes forming the fixed ferromagnetic layer of a high moment material.

11. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a second electrode includes forming the free ferromagnetic layer to include an Ru antiferromagnetically coupled tri-layer.

12. A method of fabricating a magnetic element as claimed in claim 1 wherein the step of forming a spacer layer includes forming a spacer layer having a thickness of less than 20 Å

.

13. A method of fabricating a magnetic element comprising the steps of:

forming a fixed ferromagnetic layer including a top surface and a bottom surface whose magnetic moment is fixed in a preferred direction in the presence of an applied magnetic field, the fixed ferromagnetic layer having a thickness of t₁;

forming a spacer layer on the fixed ferromagnetic layer, the spacer layer having a thickness of t₃; and

forming a free ferromagnetic layer on the spacer layer whose magnetic moment is oriented generally perpendicular to the moment of the magnetic field and is free to rotate away from said perpendicular orientation in the presence of an applied magnetic field, the free ferromagnetic layer having a thickness of t₂;

wherein 0.25t₃<

t₁<

2t₃, thereby producing near zero magnetic field at the free ferromagnetic layer.

14. A method of fabricating a magnetic element as claimed in claim 13 wherein the step of forming a spacer layer includes forming the spacer layer to include one of a dielectric material defining a MTJ structure or a conductive material defining a spin valve structure.

15. A method of fabricating a magnetic element as claimed in claim 13 further including the step of forming a high moment material located at an interface of the fixed ferromagnetic layer and the spacer layer.

16. A method of fabricating a magnetic element as claimed in claim 13 wherein the step of forming a fixed ferromagnetic layer includes forming the fixed ferromagnetic layer of a high moment material.

17. A method of fabricating a magnetic element as claimed in claim 13 wherein the step of forming a free ferromagnetic layer includes forming the free ferromagnetic layer to include an Ru antiferromagnetically coupled tri-layer.

18. A method of fabricating a magnetic element as claimed in claim 13 wherein the step of forming a spacer layer includes forming a spacer layer having a thickness of less than 20 Å

.

19. A method of fabricating a magnetic element as claimed in claims wherein the step of forming a fixed ferromagnetic layer includes forming an AF pinning layer formed adjacent the fixed ferromagnetic layer wherein the roughness of an interface h3 of the AF pinning layer, is greater than the roughness of an interface h2 of the fixed ferromagnetic layer, thereby decreasing the coupling field of the magnetic element.