Method of making a high thermal stability reference structure with out-of-plane anisotropy for magnetic device applications

• US 9,466,789 B2
• Filed: 10/10/2014
• Issued: 10/11/2016
• Est. Priority Date: 02/28/2012
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Headway Technologies Incorporated
• Inventors: Wang, Yu-Jen, Kula, Witold, Tong, Ru-Ying, Jan, Guenole
• Primary Examiner(s): BERNATZ, KEVIN M
• Application Number:
  US14/511,273
• Publication Number:
  US 20150056368A1
• Time in Patent Office: 732 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• 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: G11B 5/3929 Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding
• CPC Class Codes: G11B 5/66 the record carriers consisting of several layers
• CPC Class Codes: G11B 5/84 Processes or apparatus specially adapted for manufacturing record carriers
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/123 having a L10 crystallographic structure, e.g. [Co,Fe][Pt,Pd] thin films
• 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 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H01F 10/3295 Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers
• CPC Class Codes: H01F 41/305 applying the spacer or adjusting its interface, e.g. in order to enable particular effect different from exchange coupling
• CPC Class Codes: H03B 15/006 using spin transfer effects or giant magnetoresistance
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials
• CPC Class Codes: Y10T 428/1107 Magnetoresistive
• CPC Class Codes: Y10T 428/1121 Multilayer
• CPC Class Codes: Y10T 428/1143 : with defined structural feature

Abstract

Enhanced Hc and Hk in addition to higher thermal stability to 400° C. are achieved in magnetic devices by adding dusting layers on top and bottom surfaces of a spacer in a synthetic antiferromagnetic (SAF) structure to give a RL1/DL1/spacer/DL2/RL2 reference layer configuration where RL1 and RL2 layers exhibit perpendicular magnetic anisotropy (PMA), the spacer induces antiferromagnetic coupling between RL1 and RL2, and DL1 and DL2 are dusting layers that enhance PMA. Dusting layers are deposited at room temperature to 400° C. RL1 and RL2 layers are selected from laminates such as (Ni/Co)n, L1₀ alloys, or rare earth-transition metal alloys. The reference layer may be incorporated in STT-MRAM memory elements or in spintronic devices including a spin transfer oscillator. A transition layer such as CoFeB/Co may be formed between the RL2 reference layer and tunnel barrier layer in a bottom spin valve design.

Claims

1. A method of forming a magnetic device having high perpendicular magnetic anisotropy (PMA) comprising:

(a) depositing a seed layer on a substrate;

(b) forming a reference layer on the seed layer wherein the reference layer has a RL1/DL1/spacer/DL2/RL2 configuration in which the RL1 and RL2 layers exhibit perpendicular magnetic anisotropy, the spacer induces RKKY (antiferromagnetic coupling) between the RL1 and RL2 layers, and DL1 and DL2 are dusting layers which enhance the RKKY coupling between the RL1 and RL2 layers;

(c) forming a CoFeB/Co transitional layer on the RL2 layer;

(d) forming a non-magnetic spacer on the reference layer;

(e) depositing a free layer on the non-magnetic spacer;

(f) depositing a cap layer on the free layer to give a multilayer stack with a seed/reference layer/non-magnetic spacer/free layer/cap layer configuration; and

(g) annealing the multilayer stack.

2. The method of claim 1 wherein the dusting layers are comprised of Co, CoFe, or a Co alloy and are deposited at room temperature or at a temperature up to at least 400°

C.

3. The method of claim 1 wherein the annealing step comprises heating the multilayer stack to a temperature between 200°

C. and 500°

C. for about 1 minute to 10 hours.

4. The method of claim 1 wherein one or both of the RL1 and RL2 layers have a laminated structure represented by (Ni/Co)n, (Pd/Co)n, (Pt/Co)n, (Ni/CoFe)n, (Ni/CoFeB)n, (NiFe/Co)n, (NiFeB/Co)n, or (NiCo/Co)n where n is the number of laminations and n is between about 2 and 30.

5. The method of claim 1 wherein one or more of the RL1 and RL2 layers are a L1₀ alloy that is FePt, CoPt, FePd, NiPt, FeNi, FeCu, MnAl, MnPt, MnPd, or CuAu, or are made of a rare earth-transition metal (RE-TM) alloy.

6. The method of claim 1 wherein the free layer is a multilayer stack with a RL3/DL3/spacer/DL4/RL4 configuration in which RL3 and RL4 layers exhibit PMA, the spacer induces RKKY coupling between the RL3 and RL4 layers, and DL3 and DL4 are dusting layers that enhance the RKKY coupling between the RL3 and RL4 layers.

7. A method of forming a magnetic device having high perpendicular magnetic anisotropy (PMA) comprising:

(a) depositing a seed layer on a substrate;

(b) forming a Co/CoFeB transitional layer on the seed layer;

(c) depositing a free layer on the Co/CoFeB transitional layer wherein the free layer contacts the CoFeB layer in the transitional layer;

(d) forming a non-magnetic spacer on the free layer;

(e) forming a reference layer on the non-magnetic spacer wherein the reference layer has a Co/CoFeB/RL1/DL1/spacer/DL2/RL2 configuration in which the RL1 and RL2 layers exhibit perpendicular magnetic anisotropy, Co/CoFeB is a transitional layer, the spacer induces RKKY (antiferromagnetic coupling) between the RL1 and RL2 layers, and DL1 and DL2 are dusting layers which enhance the RKKY coupling between the RL1 and RL2 layers;

(f) depositing a cap layer on the reference layer to give a multilayer stack with a seed layer/free layer/non-magnetic spacer/reference layer/cap layer configuration; and

(g) annealing the multilayer stack.

8. The method of claim 7 wherein the DL1 and DL2 dusting layers are comprised of Co, CoFe, or a Co alloy and are deposited at room temperature or at a temperature up to about 400°

C.

9. The method of claim 7 wherein the annealing comprises heating the multilayer stack to a temperature between 200°

C. and 500°

C. for about 1 minute to 10 hours.

10. The method of claim 7 wherein one or both of the RL1 and RL2 layers have a laminated structure represented by (Ni/Co)n, (Pd/Co)n, (Pt/Co)n, (Ni/CoFe)n, (Ni/CoFeB)n, (NiFe/Co)n, (NiFeB/Co)n, or (NiCo/Co)n where n is the number of laminations and n is between about 2 and 30.

11. The method of claim 7 wherein one or more of the RL1 and RL2 layers are a L1₀ alloy that is FePt, CoPt, FePd, NiPt, FeNi, FeCu, MnAl, MnPt, MnPd, or CuAu, or are made of a rare earth-transition metal (RE-TM) alloy.

12. The method of claim 7 wherein the free layer is a multilayer stack with a FL1/DL5/spacer/DL6/FL2 configuration in which FL1 and FL2 layers exhibit PMA, the spacer induces RKKY coupling between the FL1 and FL2 layers, and DL5 and DL6 are dusting layers that enhance the RKKY coupling between the FL1 and FL2 layers.

13. A method of forming multilayer stack having a thermal stability to at least 400°

C. in a magnetic device, comprising;

(a) depositing a seed layer on a substrate; and

(b) forming a composite reference layer on the seed layer, comprising;

(1) a first reference (RL1) layer and a second reference (RL2) layer each exhibiting perpendicular magnetic anisotropy wherein the RL1 and RL2 layers are made of a laminate that is (Ni/CoFe)n, (Ni/CoFeB)n, (NiFe/Co)n, (NiFeB/Co)n, or (NiCo/Co)n where n is the number of laminations;

(2) a spacer that induces RKKY (antiferromagnetic) coupling between the RL1 and RL2 layers;

(3) a first dusting layer (DL1) and a second dusting layer (DL2) that enhance the RKKY coupling between the RL1 and RL2 layers; and

(4) a CoFeB/Co transitional layer such that the multilayer stack has a RL1/DL1/spacer/DL2/RL2/CoFeB/Co configuration.

14. The method of claim 13 wherein the spacer is Ru, Rh, Ir, Cu, or Cr and has a thickness from about 2 to 20 Angstroms.

15. The method of claim 13 wherein n is from about 2 to 30.

16. The method of claim 13 wherein the DL1 and DL2 dusting layers are made of Co, CoFe, or a Co alloy.

17. The method of claim 13 wherein the seed layer is comprised of NiCr, Ta, Pd, Pt, or Ru.

18. The method of claim 13 further comprised of forming a free layer, and a non-magnetic second spacer that is formed between the free layer and the RL2 layer.

19. The method of claim 18 wherein the free layer has a second multilayer stack with a FL1/DL5/third spacer/DL6/FL2 configuration wherein FL1 and FL2 are ferromagnetic layers that exhibit PMA, the third spacer induces RKKY coupling between the FL1 and FL2 layers, and DL5 and DL6 are dusting layers that enhance the RKKY coupling between the FL1 and FL2 layers.