Methods of fabricating three-dimensional magnetic memory devices
The various implementations described herein include methods, devices, and systems for fabricating magnetic memory devices. In one aspect, a method of fabricating a magnetic memory device includes: (1) providing a dielectric substrate with a metallic core protruding from the dielectric substrate, where: (a) a first portion of the metallic core is surrounded by the dielectric substrate and a second portion of the metallic core protrudes away from a surface of the dielectric substrate; and (b) the second portion includes: (i) a surface offset from the surface of the dielectric substrate and (ii) sidewalls extending away from the surface of the dielectric substrate to the offset surface; (2) depositing a first ferromagnetic layer on exposed surfaces of the metallic core and the dielectric substrate; (3) depositing a spacer layer on exposed surfaces of the first ferromagnetic layer; and (4) depositing a second ferromagnetic layer on exposed surfaces of the spacer layer.
1. A method of fabricating a magnetic memory device, the method comprising:
providing a dielectric substrate with a metallic core protruding from the dielectric substrate, wherein:
material composing the metallic core is deposited in a single operation;
a first portion of the metallic core is surrounded by the dielectric substrate and a second portion of the metallic core protrudes away from a surface of the dielectric substrate; and
the second portion of the metallic core comprises: (i) a surface offset from the surface of the dielectric substrate and (ii) sidewalls extending away from the surface of the dielectric substrate to the offset surface;
depositing a first ferromagnetic layer on first exposed surfaces of the metallic core and the dielectric substrate;
depositing a spacer layer on second exposed surfaces of the first ferromagnetic layer; and
depositing a second ferromagnetic layer on third exposed surfaces of the spacer layer, wherein the first ferromagnetic layer, the spacer layer, and the second ferromagnetic layer each substantially conforms to a shape of the first exposed surfaces.
2. The method of claim 1 , wherein the second portion of the metallic core is conical or cylindrical in shape.
3. The method of claim 1 , further comprising, after depositing the first ferromagnetic layer, the spacer layer, and the second ferromagnetic layer:
depositing an insulating layer on fourth exposed surfaces of the second ferromagnetic layer; and
removing portions of the first ferromagnetic layer, the spacer layer, the second ferromagnetic layer, and the insulating layer,
wherein the removing, at least:
creates and exposes an end of the first ferromagnetic layer; and
creates and exposes an end of the second ferromagnetic layer.
4. The method of claim 3 , wherein the removing comprises etching the first ferromagnetic layer, the spacer layer, the second ferromagnetic layer, and the insulating layer using ion-beam etching and/or a chemically-reactive plasma.
5. The method of claim 3 , wherein:
the insulating layer is a first insulating layer; and
the method further comprises depositing a second insulating layer on fifth exposed surfaces, including the exposed ends of the first and second ferromagnetic layers, respectively, to electrically insulate the metallic core, the first ferromagnetic layer, the spacer layer, and the second ferromagnetic layer from one another.
6. The method of claim 5 , wherein:
a thickness of the second insulating layer paralleling the sidewalls of the second portion of the metallic core is less than other thicknesses of the second insulating layer.
7. The method of claim 5 , further comprising:
removing portions of the second insulating layer to expose, at least partially, a sidewall of the second ferromagnetic layer; and
depositing a metal contact on the second insulator layer, wherein:
a shape of the metal contact substantially complements a shape of the second insulator layer; and
complementary sidewall portions of the metal contact the partially exposed sidewall of the second ferromagnetic layer.
8. The method of claim 7 , further comprising, rotating the metallic core while removing the portions of the second insulating layer to partially expose the sidewall of the second ferromagnetic layer.
9. The method of claim 7 , wherein:
removing the portions of the second insulating layer to partially expose the sidewall of the second ferromagnetic layer comprises etching the second insulating layer using ion-beam etching and/or a chemically-reactive plasma; and
a direction of the ion beam is substantially perpendicular to the sidewalls of the second portion of the metallic core during the rotating.
10. The method of claim 1 , wherein the first exposed surfaces comprise: (i) the offset surface of the metallic core, (ii) the sidewalls in the second portion of the metallic core, and (iii) the surface of the dielectric substrate.
11. The method of claim 1 , wherein a thickness of the spacer layer paralleling the sidewalls is less than other thicknesses of the spacer layer.
12. The method of claim 1 , wherein:
the dielectric substrate is positioned along a first axis;
the metallic core is positioned along a second axis; and
the first axis is substantially orthogonal to the second axis.
13. The method of claim 1 , wherein:
the surface of the dielectric substrate is a first surface;
the dielectric substrate includes a second surface that is opposite to the first surface; and
a bottom surface of the metallic core and the second surface of the dielectric substrate are coplanar.
14. The method of claim 1 , where:
providing the metallic core and the dielectric substrate comprises providing the metallic core and the dielectric substrate in a vacuum chamber; and
each depositing operation is performed using a physical vapor deposition process within the vacuum chamber.
15. The method of claim 1 , wherein the sidewalls of the second portion of the metallic core are slanted relative to the surface of the dielectric substrate.
16. The method of claim 1 , wherein the sidewalls of the second portion of the metallic core are perpendicular to the surface of the dielectric substrate.
17. The method of claim 3 , wherein:
the removing further, at least: (i) exposes the offset surface of the metallic core and (ii) partially exposes a sidewall of the second ferromagnetic layer; and
the method further comprises depositing a metal layer on surfaces newly exposed by the removing, the newly exposed surfaces including:
the offset surface of the metallic core;
the partially exposed sidewall of the second ferromagnetic layer; and
the respective ends of the first and second ferromagnetic layers.
18. The method of claim 17 , wherein the metal layer substantially conforms to a shape of the newly exposed surfaces.
19. The method of claim 17 , further comprising, after depositing the metal layer:
removing portions of the metal layer that contact (i) the offset surface of the metallic core and (ii) the respective ends of the first and second ferromagnetic layers,
wherein the metal layer remains in contact with the partially exposed sidewall of the second ferromagnetic layer.
20. The method of claim 19 , wherein:
the metallic core is connected to a first terminal; and
the second ferromagnetic layer is connected to a second terminal via the metal layer.
21. The method of claim 1 , wherein the sidewalls of the second portion of the metallic core are perpendicular to the surface of the dielectric substrate.
22. The method of claim 1 , wherein the second portion of the metallic core is formed using an etchback process.