Structure and method to reduce shorting in STT-MRAM device

• US 9,450,180 B1
• Filed: 12/14/2015
• Issued: 09/20/2016
• Est. Priority Date: 11/03/2015
• 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.
• Primary Examiner(s): Coleman, William
• Application Number:
  US14/968,287
• Time in Patent Office: 281 Days
• US Class Current: 1/1
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• 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

Abstract

A method of making a magnetic random access memory (MRAM) device includes depositing a spacer material on an electrode; forming a magnetic tunnel junction (MTJ) on the spacer material that includes a reference layer in contact with the spacer material, a free layer, and a tunnel barrier layer; patterning a hard mask on the free layer; etching the MTJ and the spacer material to transfer a pattern of the hard mask into the MTJ and the spacer material; forming an insulating layer along a sidewall of the hard mask, the MTJ, and the spacer material; disposing an interlayer dielectric (ILD) on and around the hard mask, MTJ, and spacer material; etching through the ILD to form a trench that extends to a surface and sidewall of the hard mask and a sidewall of a portion of the MTJ; and disposing a metal in the trench to form a contact electrode.

Claims

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

depositing a spacer material on an electrode;

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

patterning a hard mask on the free layer of the MTJ;

etching the MTJ and the spacer material to transfer a pattern of the hard mask into the MTJ and the spacer material;

forming an insulating layer along a sidewall of the hard mask, the MTJ, and the spacer material;

disposing an interlayer dielectric (ILD) on and around the hard mask, the MTJ, and the spacer material;

etching through the ILD to form a trench that extends to a surface and a sidewall of the hard mask and a sidewall of a portion of the MTJ; and

disposing a metal in the trench to form a contact electrode.

2. The method of claim 1, wherein the MTJ comprises a magnetic material, and etching the MTJ redeposits a portion of the magnetic material along a portion of a sidewall of the spacer beneath the insulating layer.

3. The method of claim 1, wherein etching the MTJ and the spacer material includes reactive ion etching.

4. The method of claim 1, wherein etching the MTJ and the spacer material includes ion beam etching.

5. The method of claim 1, wherein etching the MTJ and the spacer material does not substantially degrade the hard mask.

6. The method of claim 1, wherein the tunnel barrier layer is substantially free of redeposited magnetic material that accumulates during etching the MTJ.

7. The method of claim 1, wherein the spacer has a thickness in a range from about 20 to about 50 nanometers (nm).

8. The method of claim 2, wherein the redeposited magnetic material is confined to the sidewall of the spacer.

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

depositing a spacer material on an electrode;

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

patterning a hard mask on the free layer of the MTJ;

etching the MTJ and the spacer material to transfer a pattern of the hard mask into the MTJ and the spacer material;

forming an insulating layer along a sidewall of the hard mask, the MTJ, and the spacer material;

disposing an interlayer dielectric (ILD) on and around the hard mask, the MTJ, and the spacer material;

etching through the ILD to form a trench that extends to a surface of the hard mask, along a sidewall of the hard mask, and along a sidewall of a portion of the MTJ; and

disposing a metal in the trench to form a contact electrode;

wherein etching the MTJ redeposits a portion of the magnetic material of the reference layer or the free layer onto the sidewall of the spacer material beneath the insulating layer.

10. The method of claim 9, wherein the spacer material comprises ruthenium.

11. The method of claim 9, wherein the hard mask comprises tantalum nitride.

12. The method of claim 9, wherein the sidewall of the tunnel barrier layer is substantially free of the redeposited portion of the magnetic material.

13. The method of claim 9, wherein the tunnel barrier layer comprises magnesium oxide.

14. The method of claim 9, wherein etching the MTJ and the spacer material is reactive ion etching, ion beam etching, or a combination thereof.