Magnetic random access memory (MRAM) with enhanced magnetic stiffness and method of making same

• US 9,054,298 B2
• Filed: 04/04/2012
• Issued: 06/09/2015
• Est. Priority Date: 12/10/2010
• Status: Active Grant

• Current Assignee: Avalanche Technology Incorporated
• Original Assignee: Avalanche Technology Incorporated
• Inventors: Zhou, Yuchen, Huai, Yiming
• Primary Examiner(s): Cleveland, Micheal
• Assistant Examiner(s): TADAYYON ESLAMI, TABASSOM
• Application Number:
  US13/439,817
• Publication Number:
  US 20120264234A1
• Time in Patent Office: 1,161 Days
• Field of Search: 427/127, 427/128, 427/129, 427/130, 427/131, 427/132, 360/324, 428/811, 428/811.3
• US Class Current: 1/1
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01F 10/3286 Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy
• CPC Class Codes: H01F 10/329 Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect
• 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 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A spin transfer torque magnetic random access memory (STTMRAM) element and a method of manufacturing the same is disclosed having a free sub-layer structure with enhanced internal stiffness. A first free sub-layer is deposited, the first free sub-layer being made partially of boron (B), annealing is performed of the STTMRAM element at a first temperature after depositing the first free sub-layer to reduce the B content at an interface between the first free sub-layer and the barrier layer, the annealing causing a second free sub-layer to be formed on top of the first free sub-layer and being made partially of B, the amount of B of the second free sub-layer being greater than the amount of B in the first free sub-layer. Cooling down the STTMRAM element to a second temperature that is lower than the first temperature and depositing a third free sub-layer directly on top of the second free layer, with the third free sub-layer being made partially of boron (B), wherein the amount of B in the third sub-free layer is less than the amount of B in the second free sub-layer.

Claims

1. A method of manufacturing a spin transfer torque magnetic random access memory (STTMRAM) magnetic tunnel junction film stack comprising:

a) depositing a magnetic interface layer on top of a barrier layer to form a magnetic tunnel junction (MTJ);

b) annealing the STTMRAM magnetic tunnel junction film stack with the magnetic interface layer exposed on top at a first temperature;

c) cooling down the STTMRAM MTJ film stack to a second temperature that is lower than the first temperature; and

d) continuing depositing a top layer on top of the magnetic interface layer, the top layer being made of a single layer or having a multi-layer structure,

wherein steps a) and b) are carried out without exposing the MTJ film stack to atmospheric environment.

2. A method of manufacturing, as recited in claim 1, wherein the annealing is achieved with a heating element disposed beneath a substrate underlying the STTMRAM magnetic tunnel junction film stack.

3. A method of manufacturing, as recited in claim 2, wherein the heating element is made of a heating block, a heating chuck or a heating plate.

4. A method of manufacturing, as recited in claim 1, wherein the annealing is achieved with a radiation source disposed above the STTMRAM magnetic tunnel junction film stack.

5. A method of manufacturing, as recited in claim 4, wherein the radiation source is a lamp.

6. A method of manufacturing, as recited in claim 4, wherein the radiation source is a laser.

7. A method of manufacturing, as recited in claim 1, wherein the entire cycle time between start of the annealing step and end of the cooling-down step is less than 10 minutes.

8. A method of manufacturing, as recited in claim 7, wherein the entire cycle time is 2 minutes or less.

9. A method of manufacturing, as recited in claim 1, wherein the top layer is made of Co, Fe, B, Pd, Pt, Ta, Ru, Tb, Cr, Mg, O, Cu, Zn, Hf, or any combination thereof.

10. A method of manufacturing, as recited in claim 1, wherein the top layer is made of interlaced magnetic and non-magnetic layers.

11. A method of manufacturing, as recited in claim 1, wherein the magnetic interface layer is made of Co, Fe, Ta, Ti, Ni, Cr, Pt, Pd, Tb, Zn, O, Cu, Zr, or any combination thereof.

12. A method of manufacturing, as recited in claim 1, wherein the magnetic interface layer is composed of a stack of multiple magnetic layers with each of the layers of the multiple magnetic layers having a distinct boron content.

13. A method of manufacturing, as recited in claim 1, wherein the magnetic interface layer is composed of a second multilayer structure that includes magnetic and non-magnetic layers with at least one magnetic layer contacting the barrier layer.

14. A method of manufacturing, as recited in claim 13, wherein the second multilayer structure includes a top surface layer.

15. A method of manufacturing, as recited in claim 14, wherein the top surface layer is made of non-magnetic material.

16. A method of manufacturing, as recited in claim 15, wherein the top surface layer is made of a material comprising at least one element selected from the group consisting of Ta, Pd, Ru, Mg, O, Hf, Tb, Pt, Ti, Cu, and Hf.

17. A method of manufacturing, as recited in claim 14, wherein the top surface layer is made of magnetic material.

18. A method of manufacturing, as recited in claim 17, wherein the top surface layer is made of a material comprising at least one element selected from the group consisting of Co, Fe, B, Ni, Ta, Pd, Ru, Mg, O, Tb, Pt, Ti, Cu, Zr, Mn, Ir, and Hf.