METHOD OF FORMING A CARBON NANOTUBE-BASED CONTACT TO SEMICONDUCTOR

• US 20090173964A1
• Filed: 02/21/2007
• Published: 07/09/2009
• Est. Priority Date: 07/25/2001
• Status: Active Grant

• Current Assignee: Nantero Incorporated
• Original Assignee: Nantero Incorporated
• Inventors: Ward, Jonathan W., Segal, Brent M., Smith, Robert F., Meinhold, Mitchell, Schlatka, Benjamin
• Granted Patent: US 7,563,711 B1
• Time in Patent Office: Days
• US Class Current: 257/103
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 21/28575 on semiconductor bodies comprising AIIIBV compounds
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/417 carrying the current to be rectified, amplified or switched
• CPC Class Codes: H01L 29/452 on AIII-BV compounds
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/40 Materials therefor
• CPC Class Codes: Y10S 438/924 To facilitate selective etching
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

Manufacturers encounter limitations in forming low resistance ohmic electrical contact to semiconductor material P-type Gallium Nitride (p-GaN), commonly used in photonic applications, such that the contact is highly transparent to the light emission of the device. Carbon nanotubes (CNTs) can address this problem due to their combined metallic and semiconducting characteristics in conjunction with the fact that a fabric of CNTs has high optical transparency. The physical structure of the contact scheme is broken down into three components, a) the GaN, b) an interface material and c) the metallic conductor. The role of the interface material is to make suitable contact to both the GaN and the metal so that the GaN, in turn, will make good electrical contact to the metallic conductor that interfaces the device to external circuitry. A method of fabricating contact to GaN using CNTs and metal while maintaining protection of the GaN surface is provided.

Claims

1. A conductive article comprising:

a semiconductor material substrate;

a patterned conductive trace disposed on the semiconductor material substrate wherein the trace includes;

a non-woven nanotube fabric layer comprising a plurality of

unaligned nanotubes providing a plurality of conductive pathways along the extent of the trace, and

a metal layer adjacent to the non-woven nanotube fabric layer.

2. The conductive article of claim 1 wherein the metal layer is a thin film disposed on the non-woven nanotube fabric layer and wherein the metal layer is of generally planar extension and substantially parallel to the major surface of the semiconductor.

3. The conductive article of claim 2 further comprising a metal electrode disposed over and in electrical communication with the metal layer.

4. The conductive article of claim 1 wherein the non-woven nanotube fabric layer is disposed on the metal layer and wherein metal layer is a thin film of generally planar extension and substantially parallel to the major surface of the semiconductor.

5. The conductive article of claim 4, further comprising a metal electrode disposed over and in electrical communication with the non-woven nanotube fabric.

6. The patterned conductive trace of claim 1 further comprising multiple layers of metal and multiple layers of non-woven nanotube fabric, alternately disposed.

7. The patterned conductive trace of claim 6 wherein each layer of metal and each layer of non-woven nanotube fabric is of generally planar extension and substantially parallel to the major surface of the semiconductor.

8. The conductive article of claim 1 wherein at least a portion of the patterned conductive trace includes an active region, the active region constructed and arranged to be substantially optically transparent in at least a portion of the visible light range.

9. The conductive article of claim 8 wherein the metal layer is a thin film of less than 10 nanometers thickness in the dimension substantially perpendicular to the major surface of the semiconductor.

10. The conductive article of claim 1 wherein the semiconductor includes a p-GaN layer and a n-GaN layer disposed in adjacent and substantially parallel layers.

11. The conductive article of claim 1 wherein the semiconductor material substrate is selected from a set including Group III-V, V and II-VI semiconductor materials.

12. The conductive article of claim 1 wherein the non-woven nanotube fabric includes single-walled carbon nanotubes and multi-walled carbon nanotubes.

13. The conductive article of claim 1 wherein the non-woven nanotube fabric includes metallic nanotubes and semiconducting nanotubes and wherein the relative composition of metallic and semiconducting nanotubes in the fabric is controlled.

14. A light-emitting semiconductor device comprising:

a semiconductor material substrate;

a metal contact in electrical communication with the semiconductor;

an interface structure comprising a nonwoven nanotube fabric layer and a metal layer, wherein said interface structure;

is interposed between the metal contact and the semiconductor;

electrically couples the metal contact to the semiconductor; and

includes at least one active region, adjacent to said metal

contact, that is at least partially optically transparent in at least a portion of the visible light range.

15. The light-emitting semiconductor device of claim 14 wherein the interface structure constructed and arranged to provide a low resistance electrical pathway between the semiconductor and the metal contact.

16. The light-emitting semiconductor device of claim 14 wherein the semiconductor includes a p-GaN layer and a n-GaN layer disposed in adjacent and substantially parallel layers.

17. The light-emitting semiconductor device of claim 14 wherein the metal layer of the interface structure is selected and arranged to provide an ohmic contact to the layer of non-woven nanotube fabric and to the metal contact.

18. A method of making a conductive article on a semiconductor comprising:

providing a semiconductor;

forming on the semiconductor a conductive trace including a nonwoven nanotube fabric layer and a thin metal layer;

depositing a mask layer over the conductive trace;

defining a pattern in the mask layer, the pattern corresponding to the shape of the article; and

removing portions of the nanotube fabric layer and portions of the metal layer in accordance with the pattern of the mask layer so that the remaining conductive trace forms the conductive article and the semiconductor is substantially preserved.

19. The method of claim 18 wherein forming a nonwoven nanotube fabric layer includes applying carbon nanotubes via at least one of spincoating and spraycoating operations.

20. The method of claim 18 wherein removing portions of the nanotube fabric and portions of the thin metal layer in accordance with the pattern of the mask layer includes at least one of wet etching and dry etching operations.

21. The method of claim 18 further including forming a metal contact on the conductive trace wherein the metal contact is in electrical communication with the semiconductor.

22. The method of claim 21 wherein forming a metal contact includes at least one of wet etching and reactive ion etching operations.

23. The method of claim 21 wherein the thin metal layer of the conductive trace is constructed and arranged to provide a low resistance contact to the layer of non-woven nanotube fabric and to the metal contact.

24. The method of claim 18 wherein at least a portion of the conductive trace is constructed and arranged to be substantially optically transparent in at least a portion of the visible light range.

25. The method of claim 18 wherein the semiconductor includes a p-GaN layer and a n-GaN layer disposed in adjacent and substantially parallel layers.

26. The method of claim 18 wherein the semiconductor is selected from a set including Group III-V, V and II-VI semiconductor materials.

27. The method of claim 24 wherein forming a conductive trace includes disposing the thin metal layer on the nanotube fabric layer.

28. The method of claim 24 wherein forming a conductive trace includes disposing the nanotube fabric layer on thin metal layer.

29. The method of claim 24 wherein forming a conductive trace further includes providing multiple layers of carbon nanotube fabric and multiple thin layers of metal, alternately disposed.