Reduced process degradation of spin torque magnetoresistive random access memory

• US 9,853,210 B2
• Filed: 11/17/2015
• Issued: 12/26/2017
• Est. Priority Date: 11/17/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Annunziata, Anthony J., Lauer, Gen P., Marchack, Nathan P., Rossnagel, Stephen M.
• Primary Examiner(s): Sandvik, Benjamin
• Assistant Examiner(s): KHAN, FARID H
• Application Number:
  US14/943,247
• Publication Number:
  US 20170141299A1
• Time in Patent Office: 770 Days
• CPC Class Codes: H10N 50/01 Manufacture or treatment

Abstract

A method of making a magnetic random access memory (MRAM) device includes forming a magnetic tunnel junction (MTJ) on an electrode, the MTJ including a reference layer positioned in contact with the electrode, a free layer, and a tunnel barrier layer arranged between the reference layer and the free layer; and depositing an encapsulating layer on and along sidewalls of the MTJ by physical sputtering or ablation of a target material onto the MTJ.

Claims

1. A method of making a magnetic random access memory (MRAM) device, the method comprising:

forming a magnetic tunnel junction (MTJ) on an electrode, the MTJ comprising a reference layer positioned in contact with the electrode, a free layer, and a tunnel barrier layer arranged between the reference layer and the free layer; and

depositing a stoichiometric Si₃N₄ encapsulating layer directly on a top surface of the free layer and directly on sidewalls of the MTJ by physical sputtering of a target material onto the MTJ to form a silicon nitride film comprising stoichiometric Si₃N₄, the physical sputtering being performed with N₂ and Ar gases, at a temperature in a range from about 20 to about 25°

C., a power in a range from about 150 to 1000 Watts (W), and at a deposition rate in a range from about 8 Å

ngstrom/min (Å

/min) to about 20 Å

/min,

wherein the silicon nitride film comprising stoichiometric Si₃N₄ forms a final film on the top surface of the free layer and the sidewalls of the MTJ.

2. The method of claim 1, wherein physical sputtering is a physical vapor deposition (PVD) process that employs a magnetron sputter source.

3. The method of claim 1, wherein physical sputtering employs a radiofrequency (RF) diode plasma source.

4. The method of claim 1, wherein the target material is a stoichiometric Si₃N₄ target with a purity of at least 99.999%.

5. A method of making a magnetic random access memory (MRAM) device, the method comprising:

forming a magnetic tunnel junction (MTJ) on an electrode, the MTJ comprising a reference layer positioned in contact with the electrode, a free layer, and a tunnel barrier layer arranged between the reference layer and the free layer; and

depositing an encapsulating layer comprising pure aluminum directly on a top surface of the free layer and directly on sidewalls of the MTJ by using an ion beam source to ablate an aluminum target material onto the MTJ; and

exposing the encapsulating layer to pure oxygen to fully oxidize the encapsulating layer and form Al₂O₃.

6. The method of claim 5, wherein the pure aluminum is ablated in a substantially inert atmosphere.

7. The method of claim 5, wherein the pure aluminum is ablated at a temperature in a range from about 25 to about 400°

C.

8. The method of claim 5, wherein the pure aluminum has a purity of at least 99.999%.

9. The method of claim 5, further exposing the MTJ to substantially pure O₂ gas before depositing the encapsulating layer.