Spin torque MRAM fabrication using negative tone lithography and ion beam etching

Patent metadata

Field	Value
Publication number	US-9705077-B2
Application number	US-201514840176-A
Country	US
Kind code	B2
Filing date	Aug 31, 2015
Priority date	Aug 31, 2015
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

A method for forming a memory device includes masking a photoresist material using a reticle and a developer having a polarity opposite that of the photoresist to provide an island of photoresist material. A planarizing layer is etched to establish a pillar of planarizing material defined by the island of photoresist material. A metal layer is etched to form a metal pillar having a diameter about the same as the pillar of planarizing material. A memory stack is etched to form a memory stack pillar having a diameter about the same as the metal pillar. A magnetoresistive memory cell includes a magnetic tunnel junction pillar having a circular cross section. The pillar has a pinned magnetic layer, a tunnel barrier layer, and a free magnetic layer. A first conductive contact is disposed above the magnetic tunnel junction pillar. A second conductive contact is disposed below the magnetic tunnel junction pillar.

First claim

The invention claimed is:

1. A method for forming a memory device, comprising:
masking a photoresist material using a reticle and a developer having a polarity opposite that of the photoresist to provide an island of photoresist material;
etching a planarizing layer with a first etch to establish a pillar of planarizing material defined by the island of photoresist material;
etching a metal layer with a second etch to form a metal pillar having a diameter about the same as the pillar of planarizing material; and
etching a memory stack with a third etch to form a memory stack pillar having a diameter about the same as the metal pillar.

2. The method of claim 1 , wherein the photoresist material is a positive tone photoresist material, the developer is a negative tone developer, and the reticle is a dark field reticle.

3. The method of claim 1 , wherein the photoresist material is a negative tone photoresist material, the developer is a positive tone developer, and the reticle is a bright field reticle.

4. The method of claim 3 , wherein the developer is n-butyl acetate.

5. The method of claim 1 , wherein the memory stack comprises a magnetic tunnel junction formed from a fixed layer, a tunnel barrier, and a free layer.

6. The method of claim 1 , wherein the island of photoresist material is circular.

7. The method of claim 1 , further comprising etching the pillar of planarizing material to reduce a diameter of the pillar of planarizing material before etching the metal layer.

8. The method of claim 7 , wherein etching the pillar of planarizing material reduces the diameter of the pillar of planarizing material to about 70 nm.

9. The method of claim 1 , further comprising etching the memory stack pillar to reduce a diameter of the memory stack pillar.

10. The method of claim 1 , wherein the island has a diameter of about 150 nm.

11. A method for forming a memory device, comprising:
masking a photoresist material using a reticle and a developer having a polarity opposite that of the photoresist to provide an island of photoresist material;
etching a planarizing layer with a first etch to establish a pillar of planarizing material defined by the island of photoresist material;
etching the pillar with a second etch to reduce a diameter of the pillar of planarizing material;
etching a metal layer with a third etch to form a metal pillar having a diameter about the same as the pillar of planarizing material;
etching a memory stack with a fourth etch to form a memory stack pillar having a diameter about the same as the metal pillar; and
etching the memory stack pillar with a fifth etch to reduce a diameter of the memory stack pillar.

12. The method of claim 11 , wherein the photoresist material is a positive tone photoresist material, the developer is a negative tone developer, and the reticle is a dark field reticle.

13. The method of claim 11 , wherein the photoresist material is a negative tone photoresist material, the developer is a positive tone developer, and the reticle is a bright field reticle.

14. The method of claim 11 , wherein the developer is n-butyl acetate.

15. The method of claim 11 , wherein the memory stack comprises a magnetic tunnel junction formed from a fixed layer, a tunnel barrier, and a free layer.

16. The method of claim 11 , wherein the island of photoresist material is circular.

Assignees

• IBM

Inventors

• Annunziata Anthony J
• Galan Armand A
• Holmes Steve
• Joseph Eric A
• Lauer Gen P
• Lin Qinghuang
• Marchack Nathan P

Classifications

• G03F7/70425

  Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning · CPC title

• G11C11/161

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• G11C2211/5615

  Multilevel magnetic memory cell using non-magnetic non-conducting interlayer, e.g. MTJ · CPC title

• G03F7/70325

  Resolution enhancement techniques not otherwise provided for, e.g. darkfield imaging, interfering beams, spatial frequency multiplication, nearfield lenses or solid immersion lenses · CPC title

• H01L43/10

  Electricity · mapped topic