Patterning of and contacting magnetic layers

• US 8,590,139 B2
• Filed: 05/18/2010
• Issued: 11/26/2013
• Est. Priority Date: 05/18/2009
• Status: Expired due to Fees

• Current Assignee: IMEC International, Katholieke Universiteit Leuven
• Original Assignee: IMEC International, Katholieke Universiteit Leuven
• Inventors: Lagae, Liesbet, Op De Beeck, Maria, Cornelissen, Sven
• Primary Examiner(s): BERNATZ, KEVIN M
• Application Number:
  US13/202,300
• Publication Number:
  US 20120052258A1
• Time in Patent Office: 1,288 Days
• Field of Search: None
• US Class Current: 29/603.13
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: Y10T 29/49043 Depositing magnetic layer or coating
• CPC Class Codes: Y10T 29/49046 with etching or machining of magnetic material
• CPC Class Codes: Y10T 29/49048 Machining magnetic material [e.g., grinding, etching, polishing]
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Abstract

A method according to embodiments of the present invention comprises providing a magnetic stack comprising a magnetic layer sub-stack comprising magnetic layers and a bottom conductive electrode and a top conductive electrode electrically connecting the magnetic layer sub-stack at opposite sides thereof; providing a sacrificial pillar on top of the magnetic stack, the sacrificial pillar having an undercut with respect to an overlying second sacrificial material and a sloped foot with increasing cross-sectional dimension towards the magnetic stack, using the sacrificial pillar for patterning the magnetic stack, depositing an insulating layer around the sacrificial pillar, selectively removing the sacrificial pillar, thus creating a contact hole towards the patterned magnetic stack, and filling the contact hole with electrically conductive material.

Claims

1. A method for patterning and electrically contacting a magnetic stack, comprising:

providing a magnetic stack comprising a magnetic layer sub-stack comprising at least one magnetic layer and a bottom conductive electrode and a top conductive electrode electrically connecting the magnetic layer sub-stack at opposite sides thereof, wherein the magnetic layer comprises a magnetic material;

providing a sacrificial pillar on top of the magnetic stack, the sacrificial pillar having an undercut with respect to an overlying second sacrificial material and a sloped foot with increasing cross-sectional dimension towards the magnetic stack;

using the sacrificial pillar for patterning the magnetic stack by patterning the top conductive electrode and the magnetic layer to create a magnetic pillar, whereby a part of the magnetic material is redeposited onto sloped sidewalls of a patterned first sacrificial layer but not onto the magnetic layer;

depositing an insulating layer around the sacrificial pillar;

planarizing the insulating layer below a level of the second sacrificial material, whereby a portion of the sacrificial pillar is left;

selectively removing the sacrificial pillar, whereby a contact hole towards the patterned magnetic stack is created in the insulating layer; and

filling the contact hole with an electrically conductive material.

2. The method of claim 1, wherein providing a sacrificial pillar comprises:

providing a first sacrificial layer;

providing a second sacrificial material over the first sacrificial layer;

patterning the second sacrificial material;

patterning the first sacrificial layer using the patterned second sacrificial material as a mask, whereby an undercut in the first sacrificial layer is created, such that a part of the patterned first sacrificial layer remote from the magnetic stack has a width smaller than a width of the mask, and such that a part of the patterned first sacrificial layer close to the magnetic stack has a sloped bottom part which, at an interface with the magnetic stack, has a width substantially equal to the width of the mask.

3. The method of claim 2, wherein patterning the first sacrificial layer comprises using anisotropic reactive ion etching with a reactive ion plasma to achieve an undercut at a top of the first sacrificial layer underneath the patterned second sacrificial material and a sloped profile towards a bottom of the first sacrificial layer, wherein patterning is achieved by selection of a directionality and a chemical composition of the reactive ion plasma.

4. The method of claim 1, wherein depositing an insulating layer around the sacrificial pillar comprises depositing an insulating layer around the sacrificial pillar surrounded by redeposited magnetic material.

5. The method of claim 1, further comprising patterning the electrically conductive material filling the contact hole.

6. The method of claim 1, wherein providing a magnetic stack comprises providing at least one magnetic layer selected from the group consisting of Co, Fe, Ni, CoFe, CoFeB, NiFe, IrMn, and PtMn.

7. The method of claim 1, wherein providing a magnetic stack further comprises providing an additional insulating layer.

8. The method of claim 7, wherein patterning the magnetic stack is stopped in the additional insulating layer.

9. The method of claim 1, wherein providing a magnetic stack comprises providing one or more magnetic multilayers selected from the group consisting of Ta, CoFeB, MgO, CoFeB, Ru, CoFe, InMn, FeCuN, and Ta.

10. The method of claim 1, wherein providing a magnetic stack comprises providing at least one magnetic layer having a thickness I of from 1 nm to 10 nm.

11. The method of claim 1, wherein patterning the magnetic stack comprises ion milling.

12. The method of claim 1, wherein providing a sacrificial pillar comprises providing a sacrificial pillar having a height of from 100 nm to 500 nm.

13. The method of claim 1, wherein planarizing the insulating layer comprises using chemical mechanical polishing.

14. The method of claim 1, wherein selectively removing the sacrificial pillar is performed using a selective dry etching step.

15. Use of the method of claim 1 in the fabrication of any of MRAM memories, hard disk read heads and sensors, spin torque oscillators, and magnetic logic devices.

16. A device comprising a patterned stack of magnetic layers formed by the method of claim 1.