Field emission display with electron trajectory field shaping

• US 20060119248A1
• Filed: 12/07/2004
• Published: 06/08/2006
• Est. Priority Date: 12/07/2004
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Johnson, Michael R., Dean, Kenneth A., Howard, Emmett M.
• Granted Patent: US 7,429,820 B2
• Time in Patent Office: Days
• US Class Current: 313/495
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H01J 3/022 with microengineered cathode, e.g. Spindt-type

Abstract

An apparatus is provided for focusing electrons being emitted from a field emission device. The apparatus comprises a substrate (12,41,51) having first and second portions, and a cathode metal layer (20,44,52) formed over the substrate (12,41,51) in the first portion to partially define a sidewall (23) for a trench (25) in the second portion. A ballast layer (22,46,53) is formed over the substrate (12,41,51) in the second portion, the cathode metal layer (20,44,52), and the sidewall (23). A first dielectric layer (24,47,54) is formed over the ballast layer (22,46,53) in the first portion. A gate extraction metal layer (26,48,55) is formed over the first dielectric layer. At least one emitter (30) comprising a high aspect ratio conductive material is formed above the substrate and in the trench (25) having a sidewall (23) defined by the first dielectric layer (24,47,54) and the cathode metal layer (20,44,52). The ballast layer (22,46,53) extends along the sidewall and conductively contacts the cathode metal layer and the at least one emitter. An anode (32) is positioned to receive electrons from the at least one emitter (30). The ballast layer (22,46,53) provides a force that counteracts the sidewise pull of the gate extraction metal layer (26,48,55).

Claims

1. A field emission device comprising:

a substrate having first and second portions;

a cathode metal layer over the first portion to partially define a sidewall for a trench over the second portion;

a ballast layer over the second portion, the cathode metal layer, and the sidewall;

a first dielectric layer over the ballast layer over the first portion;

a gate extraction metal layer over the first dielectric layer;

at least one emitter comprising a high aspect ratio conductive material over the ballast layer in the second portion, the distance from the sidewall to the emitter being greater than the emitter height; and

an anode positioned to receive electrons from the at least one emitter.

2. The field emission device of claim 1 further comprising a second dielectric layer between the substrate and the cathode metal layer.

3. The field emission device of claim 2 further comprising a hard mask layer between the substrate and the second dielectric layer.

4. The field emission device of claim 1 further comprising a second dielectric layer between the cathode metal layer and the ballast layer.

5. The field emission device of claim 4 further comprising a hard mask layer between the substrate and the cathode metal layer.

6. The field emission device of claim 1 wherein the presence of a potential on the sidewall orients the nanotube more perpendicular to the substrate.

7. The field emission device of claim 1 wherein the emitter is a carbon nanotube.

8. The field emission device of claim 7 further comprising a catalyst above the substrate, the carbon nanotube being grown thereon.

9. The field emission device of claim 1 wherein the emitter has a height to radius ratio greater than 100.

10. The field emission device of claim 1 wherein the emitter has a length of between 0.5 and 1.5 times the height from the catalyst pad to the gate.

11. The field emission device of claim 1 wherein the ballast layer comprises one of Carbon, Silicon Carbon, Silicon Carbide, Tantalum Silicon Nitride, Tantalum Nitride, Chrome Oxi-nitride, Aluminum Nitride, or Silicon doped with one or more of Boron, Phosphorous, Arsenic, Antimony, Tantalum, or Nitrogen.

12. The field emission device of claim 1 wherein the ballast layer comprises a thickness of between 0.1 and 2.0 microns.

13. The field emission device of claim 2 wherein the second dielectric layer comprises a thickness of between 0.5 and 5.0 microns.

14. The field emission device of claim 1 wherein the at least one emitter is positioned in the trench at a depth substantially at or below the top of the gate extraction metal layer.

15. A field emission device comprising:

a substrate having first and second portions;

a hard mask over the first and second portions;

a first dielectric layer over the hard mask over the first portion;

a cathode metal layer over the first dielectric layer, wherein the first dielectric layer and the cathode metal layer partially define a sidewall for a trench over the second portion;

a ballast layer over the substrate in the second portion, the cathode metal layer, and the sidewall;

a second dielectric layer over the ballast layer over the first portion;

a gate extraction metal layer over the second dielectric layer;

at least one emitter comprising a high aspect ratio conductive material over the ballast layer over the second portion, the distance from the sidewall to the emitter being greater than the emitter height; and

an anode positioned to receive electrons from the at least one emitter.

16. The field emission device of claim 15 wherein the emitter comprises a high aspect ratio conductive material.

17. The field emission device of claim 15 wherein the emitter is a carbon nanotube.

18. The field emission device of claim 17 wherein the presence of a potential on the sidewall orients the nanotube more perpendicular to the substrate.

19. The field emission device of claim 17 further comprising a catalyst formed over the second portion, the carbon nanotube being grown thereon.

20. The field emission device of claim 15 wherein the emitter has a height to radius ratio greater than 100.

21. The field emission device of claim 15 wherein the emitter has a length of between 0.5 and 1.5 times the height from the catalyst pad to the gate.

22. The field emission device of claim 15 wherein the ballast layer comprises one of Carbon, Silicon Carbon, Silicon Carbide, Tantalum Silicon Nitride, Tantalum Nitride, Chrome Oxi-nitride, Aluminum Nitride, or Silicon doped with one or more of Boron, Phosphorous, Arsenic, Antimony, Tantalum, or Nitrogen.

23. The field emission device of claim 15 wherein the ballast layer comprises a thickness of between 0.1 and 2.0 microns.

24. The field emission device of claim 15 wherein the first dielectric layer comprises a thickness of between 0.5 and 5.0 microns.

25. The field emission device of claim 15 wherein the at least one emitter is positioned in the trench at a depth substantially at or below the top of the gate extraction metal layer.

26. A field emission device comprising:

a substrate having first and second portions;

a hard mask over the first and second portions;

a cathode metal layer over the hard mask over the first portion;

a first dielectric layer over the cathode metal layer, wherein the first dielectric layer and the cathode metal layer partially define a sidewall for a trench in the second portion;

a ballast layer over the substrate in the second portion, the first dielectric layer, and the sidewall;

a second dielectric layer over the ballast layer over the first portion;

a gate extraction metal layer over the second dielectric layer;

at least one emitter comprising a high aspect ratio conductive material over the ballast layer in the second portion, the distance from the sidewall to the emitter being greater than the emitter height; and

an anode positioned to receive electrons from the at least one emitter.

27. The field emission device of claim 26 wherein the emitter comprises a high aspect ratio conductive material.

28. The field emission device of claim 26 wherein the emitter is a carbon nanotube.

29. The field emission device of claim 28 wherein the presence of a potential on the sidewall orients the nanotube more perpendicular to the substrate.

30. The field emission device of claim 28 further comprising a catalyst over the second portion, the carbon nanotube being grown thereon.

31. The field emission device of claim 26 wherein the emitter has a height to radius ratio greater than 100.

32. The field emission device of claim 26 wherein the emitter has a length of between 0.5 and 1.5 times the height from the catalyst pad to the gate.

33. The field emission device of claim 26 wherein the ballast layer comprises one of Carbon, Silicon Carbon, Silicon Carbide, Tantalum Silicon Nitride, Tantalum Nitride, Chrome Oxi-nitride, Aluminum Nitride, or Silicon doped with one or more of Boron, Phosphorous, Arsenic, Antimony, Tantalum, or Nitrogen.

34. The field emission device of claim 26 wherein the ballast layer comprises a thickness of between 0.1 and 2.0 microns.

35. The field emission device of claim 26 wherein the first dielectric layer comprises a thickness of between 0.5 and 5.0 microns.

36. The field emission device of claim 26 wherein the at least one emitter is positioned in the trench at a depth substantially at or below the top of the gate extraction metal layer.

37. A field emission device comprising:

a first material defining a trench having a sidewall and a bottom;

a ballast layer on the sidewall of the trench, the ballast layer adapted to receive a potential; and

at least one emitter comprising a high aspect ratio conductive material positioned in the trench and coupled to the ballast layer, wherein the presence of a potential on the ballast layer on the sidewall exerts a force that tends to orient the nanotube parallel to the sidewall.