Capping structure for enhancing dR/R of the MTJ device

• US 7,449,345 B2
• Filed: 06/15/2004
• Issued: 11/11/2008
• Est. Priority Date: 06/15/2004
• Status: Expired due to Fees

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Applied Spintronics, Inc., Headway Technologies Incorporated (TDK Corporation)
• Inventors: Tong, Ru-Ying, Hong, Liubo, Li, Min, Horng, Cheng T.
• Primary Examiner(s): Menz; Douglas M.
• Assistant Examiner(s): Such; Matthew W
• Application Number:
  US10/868,715
• Publication Number:
  US 20050276099A1
• Time in Patent Office: 1,610 Days
• Field of Search: 438/3, 257421-428, 257E43001-E43007, 427127-132, 428800-8489
• 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: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

An MTJ in an MRAM array or in a TMR read head is comprised of a capping layer with a lower inter-diffusion barrier layer, an intermediate oxygen gettering layer, and an upper metal layer that contacts a top conductor. The composite capping layer is especially useful with a moderate spin polarization free layer such as a NiFe layer with a Fe content of about 17.5 to 20 atomic %. The capping layer preferably has a Ru/Ta/Ru configuration in which the lower Ru layer is about 10 to 30 Angstroms thick and the Ta layer is about 30 Angstroms thick. As a result, a high dR/R of about 40% is achieved with low magnetostriction less than about 1.0 E−6 in an MTJ in an MRAM array. Best results are obtained with an AlOx tunnel barrier layer formed by an in-situ ROX process on an 8 to 10 Angstrom thick Al layer.

Claims

1. A method of forming an MTJ element on a substrate, comprising:

(a) sequentially forming a seed layer, an AFM layer, a pinned layer, and a tunnel barrier layer on a substrate;

(b) forming a moderate spin polarization free layer on the tunnel barrier layer; and

(c) forming a capping layer on said moderate spin polarization free layer wherein said capping layer is comprised of a lower inter-diffusion barrier layer comprised of Ru that contacts said moderate spin polarization free layer, a middle oxygen gettering layer made of Ta, and an oxidation resistant upper metal layer formed on the middle oxygen gettering layer, said oxidation resistant upper metal layer is comprised of Ru and has a top surface that is essentially planar and all layers in said capping layer that has a Ru/Ta/Ru configuration have substantially the same width.

2. The method of claim 1 wherein the substrate is a bottom conductor in an MRAM structure.

3. The method of claim 2 further comprised of forming a top conductor on the top surface of said upper metal layer.

4. The method of claim 2 wherein said tunnel barrier layer is comprised of AlOx and is formed by depositing an Al layer with a thickness of about 8 to 10 Angstroms on said pinned layer and then performing an in-situ radical oxidation (ROX) process.

5. The method of claim 2 wherein the moderate spin polarization free layer is comprised of NiFe with an Fe content from about 17.5 to 20 atomic % and a thickness of about 20 to 50 Angstroms.

6. The method of claim 1 wherein the substrate is a shield capping layer on a bottom shield in a TMR read head.

7. The method of claim 6 further comprised of forming an upper shield on the top surface of said oxidation resistant upper metal layer.

8. The method of claim 6 wherein said tunnel barrier layer is comprised of AlOx and is formed by depositing an Al layer with a thickness of about 5 to 6 Angstroms on said pinned layer and then performing an in-situ natural oxidation (NOX) process.

9. The method of claim 6 wherein the moderate spin polarization free layer is a composite CoFe/NiFe layer comprised of CoFe with a Fe content of about 10 atomic % and a thickness of about 5 to 10 Angstroms and NiFe with a Fe content from about 17.5 to 20 atomic % and a thickness of about 30 to 40 Angstroms.

10. The method of claim 1 wherein the seed layer is comprised of NiCr, the AFM layer is comprised of MnPt, and the pinned layer is a SyAP pinned layer comprised of a lower CoFe layer that has a Fe content of about 10 atomic %, a middle Ru coupling layer, and an upper CoFe layer that has a Fe content from 25 to 50 atomic %.

11. The method of claim 1 wherein the lower inter-diffusion barrier layer has a thickness of about 10 to 30 Angstroms.

12. The method of claim 1 wherein said middle oxygen gettering layer has a thickness between about 20 and 50 Angstroms.

13. The method of claim 1 wherein the oxidation resistant upper metal layer has a thickness of about 100 to 250 Angstroms.

14. The method of claim 1 wherein all layers in the MTJ element are deposited in an ultra high vacuum sputtering system comprised of sputtering chambers and an oxidation chamber wherein all layers are formed after a single pump down step.

15. The method of claim 1 wherein said substrate has an upper amorphous Ta layer that promotes smooth and dense growth in the layers within said MTJ element.