Patterned growth of single-walled carbon nanotubes from elevated wafer structures

• US 7,022,541 B1
• Filed: 11/18/2002
• Issued: 04/04/2006
• Est. Priority Date: 11/19/2001
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Dai, Hongjie, Yenilmez, Erhan
• Primary Examiner(s): Booth, Richard A.
• Application Number:
  US10/299,978
• Time in Patent Office: 1,233 Days
• Field of Search: 438/1, 438/466, 438/780, 438/782, 438/951
• US Class Current: 438/52
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01Q 70/12 Nanotube tips
• CPC Class Codes: Y10S 438/951 Lift-off
• CPC Class Codes: Y10S 977/843 Gas phase catalytic growth, i.e. chemical vapor deposition

Abstract

A wafer-scale fabrication approach for manufacturing single-walled carbon nanotube (SWNT) tips is implemented. Catalyst material is selectively placed (e.g., patterned) onto a plurality of prefabricated elevated structures (e.g., silicon tips) on a wafer. SWNTs are grown protruding from the catalyst on the elevated structures. The resulting SWNT protruding from a tip can be implemented in a variety of applications, such as in atomic force microscopy (AFM). With this approach, nanotube tips can be implemented for a variety of applications, including advanced nanoscale imaging, imaging of solid-state and soft biological systems and for scanning probe lithography.

Claims

1. A method for manufacturing a plurality of nanotube tips, the method comprising:

forming a removable layer on a portion of a wafer having elevated structures extending therefrom, at least a portion of the elevated structures being substantially free of the removable layer;

forming catalyst material on the removable layer and on the at least a portion of the elevated structures being substantially free of the removable layer;

removing the removable layer and the catalyst material thereon, leaving catalyst material on a portion of the elevated structures; and

growing single-walled carbon nanotube tips from the plurality of elevated structures using the catalyst material.

2. The method of claim 1, wherein forming catalyst material comprises:

spin-coating a catalyst suspension on the wafer; and

wherein removing the removable layer includes removing a portion of the catalyst suspension.

3. The method of claim 2, wherein forming a removable layer comprises:

forming a photoresist layer on the wafer and leaving at least a portion of the elevated structures exposed;

wherein spin-coating a catalyst suspension on the wafer includes spin-coating a catalyst suspension on the photoresist layer and on the exposed portion of the elevated structures; and

wherein removing a portion of the catalyst suspension includes removing a portion of the photoresist layer having catalyst suspension thereon.

4. The method of claim 3, wherein forming a photoresist layer includes spin-coating the photoresist layer on a portion of the wafer that does not include an upper portion of the elevated structures.

5. The method of claim 2, wherein removing the removable layer and the catalyst material thereon includes lifting off the removable layer with a solvent.

6. The method of claim 5, wherein lifting off the removable layer with a solvent includes using acetone to dissolve a portion of the removable layer.

7. The method of claim 1, wherein forming catalyst material includes selectively placing a metal salt on the elevated structures and configured and arranged for growing at least one nanotube from each elevated structure.

8. The method of claim 1, wherein forming catalyst material includes selectively placing the catalyst material on sidewalls of the elevated structures that extend from the wafer.

9. The method of claim 1, wherein forming catalyst material includes selectively placing a thin layer of catalyst material around at least a portion of an elevated structure.

10. The method of claim 1, wherein growing single-walled carbon nanotube tips includes using a carbon-containing gas as feedstock and CVD growing the single-walled carbon nanotube tips.

11. The method of claim 10, wherein growing single-walled carbon nanotube tips includes using a hydrogen co-flow for the CVD growth.

12. The method of claim 11, wherein using a hydrogen co-flow includes using a hydrogen co-flow having flowrate characteristics selected to inhibit carbon pyrolysis while maintaining the growth of the single-walled carbon nanotube tips.

13. The method of claim 1, wherein forming catalyst material includes selectively placing catalyst material on at least 300 elevated structures and wherein growing single-walled carbon nanotube tips includes growing single-walled carbon nanotube tips from at least 85% of the at least 300 elevated structures.

14. The method of claim 1, further comprising shortening the length of at least one of the single-walled carbon nanotube tips.

15. The method of claim 14, wherein shortening the length of the at least one of the single-walled carbon nanotube tips includes applying an electric bias voltage between the single-walled carbon nanotube tip and a doped silicon substrate and oxygen discharge etching the single-walled carbon nanotube tip.

16. The method of claim 15, wherein forming a removable layer on a portion of a wafer having elevated structures extending therefrom includes forming a removable layer on a portion of a wafer having cantilevers, each cantilever having an elevated structure, further comprising applying the single-walled carbon nanotube tip against the substrate by oscillating the cantilever and obtaining a force curve for the single-walled carbon nanotube tip, wherein shortening the length of the at least one of the single-walled carbon nanotube tips includes shortening the length of the single-walled carbon nanotube tip until the force curve reaches an amplitude threshold that indicates that a rigid and non-sticking nanotube tip is obtained.

17. The method of claim 14, wherein shortening the length of the at least one of the single-walled carbon nanotube tips includes electrically discharging a portion of the at least one of the single-walled carbon nanotube tips.

18. The method of claim 1, further comprising:

removing one of the plurality of elevated structures having a single-walled carbon nanotube tip from the wafer; and

mounting the removed elevated structure onto a testing arrangement.

19. The method of claim 18, wherein mounting the removed elevated structure onto a testing arrangement includes mounting the removed elevated structure onto an atomic force microscopy arrangement.

20. The method of claim 1, wherein forming catalyst material comprises evaporating a sub-nanometer thick iron film onto the elevated structures, where the iron film is adapted to catalyze the growth of carbon nanotubes from the elevated structure.

21. The method of claim 1, wherein forming catalyst material comprises patterning the catalyst during the manufacture of the wafer.

22. The method of claim 1, wherein growing single-walled carbon nanotube tips includes growing nanotubes that include carbon and another type of atom.

23. The method of claim 1, wherein growing single-walled carbon nanotube tips includes growing probe tips for atomic force microscopy.

24. A method for manufacturing a plurality of probe tips, the method comprising:

spin-coating a photoresist onto a wafer having a plurality of elevated structures and leaving at least a portion of the elevated structures exposed and substantially free from photoresist;

forming catalyst suspension material on a portion of the photoresist and the exposed elevated structures;

after forming the catalyst suspension material, removing the photoresist and a portion of the catalyst suspension material thereon with a solvent, leaving catalyst material on sidewalls of the plurality of elevated structures;

placing the wafer into a CVD chamber; and

heating the CVD chamber and growing single-walled carbon nanotube probe tips extending from the catalyst suspension material on the plurality of elevated structures.