Electronic fuse with conformal fuse element formed over a freestanding dielectric spacer

• US 20070210890A1
• Filed: 03/09/2006
• Published: 09/13/2007
• Est. Priority Date: 03/09/2006
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Yang, Chih-Chao, Tonti, William, Hsu, Louis, Mandelman, Jack
• Granted Patent: US 7,460,003 B2
• Time in Patent Office: Days
• US Class Current: 337/159
• CPC Class Codes: H01L 23/5256 comprising fuses, i.e. connections having their state changed from conductive to non-conductive
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: Y10T 29/49107 Fuse making

Abstract

An electronic fuse for an integrated circuit and a method of fabrication thereof are presented. The electronic fuse has a first terminal portion and a second terminal portion interconnected by a fuse element. The fuse element has a convex upper surface and a lower surface with a radius of curvature at a smallest surface area of curvature less than or equal to 100 nanometers. Fabricating the electronic fuse includes forming an at least partially freestanding dielectric spacer above a supporting structure, and then conformably forming the fuse element of the fuse over at least a portion of the freestanding dielectric spacer, with the fuse element characterized as noted above. The dielectric spacer may remain in place as a thermally insulating layer underneath the fuse element, or may be removed to form a void underneath the fuse element.

Claims

1. A fuse for an integrated circuit, the fuse comprising:

a first terminal portion and a second terminal portion interconnected by a fuse element,

wherein the fuse element has a convex upper surface and a lower surface with a radius of curvature at a smallest surface area of curvature less than or equal to 100 nanometers.

2. The fuse of claim 1, wherein the fuse element resides over a void in a supporting structure.

3. The fuse of claim 1, wherein the fuse element resides above a thermally insulating, dielectric spacer.

4. The fuse of claim 3, wherein the fuse element is conformably disposed over at least a portion of the thermally isolating, dielectric spacer.

5. The fuse of claim 4, wherein the thermally isolating, dielectric spacer has a quadrant-shaped cross-section.

6. The fuse of claim 1, wherein the upper surface of the fuse element is convex for a majority of the distance between the first terminal portion and the second terminal portion.

7. The fuse of claim 1, wherein the lower surface of the fuse element is planar in a vertical direction for a portion thereof, and wherein the smallest surface area of curvature is adjacent to the planar portion of the lower surface.

8. The fuse of claim 7, wherein the planar portion of the lower surface of the fuse element is oriented orthogonal to a plane containing at least one of an upper surface of the first terminal portion or an upper surface of the second terminal portion.

9. The fuse of claim 1, wherein the first terminal portion is electrically contacted from both above and below, and the second terminal portion is electrically contacted from above only, with a dielectric material being disposed below, and wherein the first terminal portion is electrically contacted from below via an underlying metal.

10. The fuse of claim 1, wherein the fuse is an electrically programmable fuse, the fuse element has a minimum thickness T_min≦

5 nm between the upper surface and lower surface, and the fuse has a minimum length less than 70 nm, and wherein the fuse is programmable at an operating voltage of the integrated circuit less than 3 volts.

11. The fuse of claim 1, wherein enhanced current density, heat generation, and temperature rise are obtained in a region of the fuse element adjacent to the smallest area of curvature in the lower surface thereof having the radius of curvature less than or equal to 100 nanometers.

12. A method of fabricating a fuse for an integrated circuit, the method comprising:

forming an at least partially freestanding dielectric spacer above a supporting structure; and

conformably forming a fuse element of the fuse over at least a portion of the freestanding dielectric spacer, wherein the fuse element has a convex upper surface and a lower surface with a radius of curvature at a smallest surface area of curvature less than or equal to 100 nanometers.

13. The method of claim 12, wherein the freestanding dielectric spacer is a sacrificial spacer, and wherein the method further comprises removing the sacrificial spacer after conformably forming the fuse element over the at least a portion thereof to define a void underneath the fuse element.

14. The method of claim 13, wherein the forming of the at least partially freestanding dielectric spacer comprises forming the dielectric spacer from at least one of germanium, silicon nitride, silicon carbide, hydrogenated silicon carbide or nitrogenated silicon carbide.

15. The method of claim 12, wherein forming the freestanding dielectric spacer comprises forming the freestanding dielectric spacer with a quadrant-shaped cross-section.

16. The method of claim 12, wherein the fuse comprises a first terminal portion and a second terminal portion interconnected by the fuse element, and wherein the freestanding dielectric spacer is thermally insulating, and the conformably forming of the fuse element comprises forming the fuse element over the at least a portion of the freestanding dielectric spacer, with the upper surface of the fuse element being convex for a majority of the distance between the first terminal portion and the second terminal portion of the fuse.

17. The method of claim 16, wherein the forming of the freestanding dielectric spacer further comprises forming at least a portion of the freestanding dielectric spacer to comprise a vertically oriented surface, and wherein the conformably forming of the fuse element over the at least a portion of the freestanding dielectric spacer results in the lower surface of the fuse element being vertically straight over a portion thereof, wherein the vertically straight portion of the lower surface is oriented orthogonal to a plane containing at least one of an upper surface of the first terminal portion or an upper surface of the second terminal portion.

18. The method of claim 12, wherein the fuse comprises a first terminal portion and a second terminal portion interconnected by the fuse element, and wherein the conformably forming comprises forming the fuse element with a variable thickness, wherein a thickness of the fuse element is thinner in a middle region thereof compared with regions of the fuse element adjacent to the first terminal portion and the second terminal portion of the fuse.