COBALT (CO) AND PLATINUM (PT)-BASED MULTILAYER THIN FILM HAVING INVERTED STRUCTURE AND METHOD FOR MANUFACTURING SAME

• US 20150115379A1
• Filed: 06/26/2012
• Published: 04/30/2015
• Est. Priority Date: 05/22/2012
• Status: Active Grant

• Current Assignee: SK Hynix Inc.
• Original Assignee: SK Hynix Inc.
• Inventors: Lee, Tae Young, Lee, Seong Rae, Lim, Sang Ho, Son, Dong-Su
• Granted Patent: US 9,705,075 B2
• Time in Patent Office: Days
• US Class Current: 257/421
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• 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 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

The present invention relates to a cobalt (Co) and platinum (Pt)-based multilayer thin film having a novel structure and perpendicular magnetic anisotropy, and to a fabrication method thereof. More specifically, the invention relates to a cobalt and platinum-based multilayer thin film having perpendicular magnetic anisotropy (PMA), which includes thin cobalt layers and thin platinum layers alternately deposited over a substrate, and has an inverted structure in which a thickness of the thin cobalt layers is greater than that of the thin platinum layers, and to a fabrication method thereof. The cobalt and platinum-based multilayer thin film has a new structure in which the thickness of a magnetic thin layer is greater than that of a non-magnetic thin layer. The multilayer thin film may be easily applied as a free layer and a pinned layer in a magnetic tunnel junction by controlling the perpendicular magnetic anisotropy energy depending on the thickness ratio of the layers. Also, the multilayer thin film has excellent thermal stability, and thus maintains its PMA energy density even after being subjected to a heat treatment process. In addition, it enables a fine amount of in-plane magnetic anisotropy to be formed by heat treatment so as to reduce the critical current density required for magnetization switching. Therefore, it may be advantageously used for high-performance and high-density MRAM.

Claims

1. A cobalt and platinum-based multilayer thin film having perpendicular magnetic anisotropy (PMA), comprising:

thin cobalt layers and thin platinum layers alternately deposited over a substrate,

wherein the cobalt and platinum-based multilayer thin film has an inverted structure in which a thickness of the thin cobalt layers is greater than that of the thin platinum layers, and

wherein a ratio of the thickness of the thin cobalt layers to that of the thin platinum layers in the cobalt and platinum-based multilayer thin film is more than 1;

1 but less than 3;

1.

2. The cobalt and platinum-based multilayer thin film of claim 1, wherein the cobalt and platinum-based multilayer thin film has a highest value of a PMA energy density.

3. The cobalt and platinum-based multilayer thin film of claim 1, wherein the thickness of each of the thin platinum layers in the cobalt and platinum-based multilayer thin film ranges from 0.15 nm to 0.25 nm.

4. The cobalt and platinum-based multilayer thin film of claim 1, wherein the thin cobalt layer and the thin platinum layer in the cobalt and platinum-based multilayer thin film are deposited once or are alternately deposited 2-10 times.

5. The cobalt and platinum-based multilayer thin film of claim 1, wherein the substrate is one selected from the group consisting of a silicon substrate, a glass substrate, a sapphire substrate and a magnesium oxide substrate.

6. The cobalt and platinum-based multilayer thin film of claim 1, wherein a buffer layer and a seed layer are deposited between the substrate and the alternately deposited thin cobalt layer and thin platinum layer, and a protective layer is deposited on the alternately deposited thin cobalt layer and thin platinum layer.

7. The cobalt and platinum-based multilayer thin film of claim 6, wherein the buffer layer, the seed layer or the protective layer is made of Au, Cu, Pd, Pt, Ta, Ru, or an alloy of two or more thereof.

12. The cobalt and platinum-based multilayer thin film of claim 1, wherein a critical current value required for a perpendicular magnetization switching is reduced by forming in-plane magnetic anisotropy after heat treatment of the cobalt and platinum-based multilayer thin film.

8. A method for fabricating a cobalt and platinum-based multilayer thin film, the method comprising the steps of:

(a) depositing, over a substrate, a cobalt and platinum-based multilayer thin film having an inverted structure in which a thickness of thin cobalt layers is greater than that of thin platinum layers; and

(b) heat-treating the multilayer thin film.

9. The method of claim 8, wherein the heat-treating is performed at a temperature between 150°

C. and 500°

C.

10. The method of claim 8, further comprising, before step (a), a step of sequentially depositing a buffer layer and a seed layer over the substrate.

11. The method of claim 8, further comprising, after step (a) and before step (b), a step of depositing a protective layer.

13. A magnetic tunnel junction (MTJ) comprising:

a cobalt and platinum-based multilayer thin film having perpendicular magnetic anisotropy (PMA),

wherein the cobalt and platinum-based multilayer thin film comprises;

thin cobalt layers and thin platinum layers alternately deposited over a substrate,

wherein the cobalt and platinum-based multilayer thin film has an inverted structure in which a thickness of the thin cobalt layers is greater than that of the thin platinum layers, and

wherein a ratio of the thickness of the thin cobalt layers to that of the thin platinum layers in the cobalt and platinum-based multilayer thin film is more than 1;

1 but less than 3;

1.

14. The MTJ of claim 13, wherein the cobalt and platinum-based multilayer thin film is applied as a free layer or a fixed layer in the MTJ by controlling a PMA energy density depending on a thickness ratio of the thin platinum layers and the thin cobalt layers.

15. A cobalt and platinum-based multilayer thin film having perpendicular magnetic anisotropy (PMA), comprising:

thin cobalt layers and thin platinum layers alternately deposited over a substrate,

wherein the cobalt and platinum-based multilayer thin film has an inverted structure in which a thickness of the thin cobalt layers is greater than that of the thin platinum layers.

16. The cobalt and platinum-based multilayer thin film of claim 15, wherein the thickness of each of the thin platinum layers in the cobalt and platinum-based multilayer thin film ranges from 0.15 nm to 0.25 nm.

17. The cobalt and platinum-based multilayer thin film of claim 15, wherein the thin cobalt layer and the thin platinum layer in the cobalt and platinum-based multilayer thin film are deposited once or are alternately deposited 2-10 times.

18. The cobalt and platinum-based multilayer thin film of claim 15, wherein the substrate is one selected from the group consisting of a silicon substrate, a glass substrate, a sapphire substrate and a magnesium oxide substrate.

19. The cobalt and platinum-based multilayer thin film of claim 15, wherein a buffer layer and a seed layer are deposited between the substrate and the alternately deposited thin cobalt layer and thin platinum layer, and a protective layer is deposited on the alternately deposited thin cobalt layer and thin platinum layer.