Method of producing regular arrays of nano-scale objects using nano-structured block-copolymeric materials

• US 20030185985A1
• Filed: 01/30/2003
• Published: 10/02/2003
• Est. Priority Date: 02/01/2002
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Bronikowski, Michael J., Hunt, Brian D.
• Granted Patent: US 7,115,305 B2
• Time in Patent Office: Days
• US Class Current: 427/258
• CPC Class Codes: B81B 2203/0361 Tips, pillars
• CPC Class Codes: B81C 1/00031 Regular or irregular arrays of nanoscale structures, e.g. etch mask layer photomechanical, e.g. photolithographic, production of textured or patterned surfaces G03F7/00; lithographic processes for making patterned surfaces using printing and stamping G03F7/0002
• CPC Class Codes: B81C 2201/0149 Forming nanoscale microstructures using auto-arranging or self-assembling material
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/08 Aligned nanotubes
• CPC Class Codes: C01B 2202/36 Diameter
• CPC Class Codes: C01B 32/162 characterised by catalysts
• CPC Class Codes: Y10S 977/844 Growth by vaporization or dissociation of carbon source using a high-energy heat source, e.g. electric arc, laser, plasma, e-beam

Abstract

A method of forming a periodic array of nano-scale objects using a block copolymer, and nano-scale object arrays formed from the method are provided. The method for forming the arrays generally includes the steps of depositing a block copolymer of at least two blocks on a substrate to form an ordered meso-scale structured array of the polymer materials, forming catalytic metal dots based on the meso-scale structure, and growing nano-scale objects on the catalytic dots to form an ordered array of nano-scale objects.

Claims

1. A method of forming an ordered array of nanofeatures comprising the steps of:

depositing a block copolymer on a substrate, wherein the block copolymer comprises at least two different blocks, and wherein the block copolymer can self-assemble into an ordered polymeric array of a plurality of regular nanometer-scale structures;

activating the block-copolymer to self-assemble to form the polymeric array;

applying a catalytic material, wherein the catalytic material is chosen such that an ordered catalytic material array is formed comprising a plurality of catalytic nucleation regions and having a structure defined by the polymeric array;

removing the polymeric array from the substrate such that only the catalytic material array remains; and

growing nanofeatures on the catalytic material array to form an ordered nanofeature array having a structure defined by the catalytic material array.

2. The method described in claim 1, wherein the catalytic material is deposited onto the substrate along with the block copolymer such that the catalytic material preferentially binds to one of the at least two different blocks such that the catalytic material array is formed contemporaneously with the ordered polymeric array.

3. The method described in claim 1, further comprising the step of selectively removing the nanometer-scale structures made from one of the at least two different blocks from the substrate to create a plurality of voids in the polymeric array prior to the application of the catalytic material such that the catalytic material bonds within the voids to form the catalytic material array.

4. The method described in claim 3, wherein the step of selectively removing comprises a removal method selected from the group consisting of a UV induced decomposition, reactive ion etching, acid-base reaction, and oxidation.

5. The method described in claim 1, wherein each of the at least two different blocks is made of at least one polymer monomer, and wherein the size, shape, and spacing of the nanometer-scale structures depends on the size and number of the polymer monomers in each of the at least two different blocks.

6. The method described in claim 1, wherein the size of the catalytic nucleation regions depends on the length of the block to which the catalytic material preferentially binds.

7. The method described in claim 1, wherein the spacing between the catalytic nucleation regions depends on the length of the block to which the catalytic material does not preferentially bind.

8. The method described in claim 1, wherein the at least two different blocks self-assemble based on dipole interactions.

9. The method described in claim 1, wherein the block copolymer is an amphiphilic block copolymer.

10. The method described in claim 1, wherein the catalytic material preferentially binds to one of the at least two different blocks based on the polarity of the at least two different blocks.

11. The method described in claim 1, wherein the step of depositing comprises spin-coating a solution containing the block copolymer onto the substrate.

12. The method described in claim 1, wherein the step of activating includes annealing the polymer coated substrate.

13. The method described in claim 1, wherein the step of applying comprises a method selected from one of vapor deposition and electrochemical application.

14. The method described in claim 1, wherein the step of removing is selected from the group consisting of reactive ion etching, oxidation, and solvation.

15. The method described in claim 1, wherein the step of growing the nanofeatures further comprises heating the substrate bearing the catalytic material array under a flow of a carbon-containing gas capable of reacting on the catalytic nucleation regions to form the nanofeatures.

16. The method described in claim 15, wherein the step of heating takes place in the presence of an additional gas selected from the group consisting of argon, nitrogen, and ammonia.

17. The method described in claim 15, wherein the step of heating takes place in a vacuum chamber at sub-atmospheric pressure.

18. The method described in claim 15, wherein the substrate is heated to a temperature of about 600 to about 900°

C.

19. The method described in claim 15, wherein the carbon-containing gas is selected from the group consisting of methane, ethylene, acetylene, and carbon monoxide.

20. The method described in claim 1, further comprising restricting the size of the nanofeature array by a method selected from one of photomasking and electron beam lithography.

21. The method described in claim 1, wherein the substrate is a complex shape selected from the group consisting of curve, corrugated and tubular.

22. The method described in claim 1, wherein the nanometer-scale structures are selected from one of cylinders and spheres.

23. The method described in claim 1, wherein the nanofeatures are a shape selected from the group consisting of tubes, spheres, pyramids and rectangles.

24. The method described in claim 1, wherein nanofeatures are carbon nanotubes.

25. The method described in claim 24, wherein the carbon nanotubes have a uniform diameter.

26. The method described in claim 1, wherein at least two differently dimensioned nanofeatures are grown on the substrate.

27. The method described in claim 1, wherein the nanofeatures have a cross-sectional dimension of about 10 to 100 nm.

28. The method described in claim 1, wherein the nanofeature array has a lattice spacing of about 10 to 100 nm.

29. The method described in claim 1, wherein the nanofeatures are functionalized.

30. The method described in claim 1, wherein the nanofeatures are made from a material selected from the group consisting of metal oxides, silicon, or silicon dioxide.

31. The method described in claim 1, wherein the substrate is selected from the group consisting of metals, silicon dioxide, silicon, alumina, glass, and polymeric plastic.

32. The method described in claim 1, wherein the catalytic material is selected from the group consisting of Mo, W, Pd, Fe, Ni, Co and a Ni/Co alloy.

33. The method described in claim 1, wherein the catalytic material is applied as an ionic metal salt.

34. The method described in claim 33, wherein the ionic metal salt is selected from the group consisting of iron chloride, iron nitrate, nickel chloride, nickel nitrate, cobalt chloride, and cobalt nitrate.

35. The method described in claim 1, wherein the catalytic material is applied as an organometallic compound.

36. The method described in claim 35, wherein the organometallic compound is selected from the group consisting of metal carbonyls, metallocenes, and acetylacetonates.

37. The method described in claim 1, wherein the at least two different blocks are polystyrene and polymethylmethacrylate.

38. The method described in claim 37, wherein the polystyrene block has a length of about 100 to 1000 styrene monomers.

39. The method described in claim 37, wherein the polymethylmethacrylate block has a length of about 50 to 200 methylmethacrylate monomers.

40. The method described in claim 37, wherein the nanometer-scale structures comprise polymethylmethacrylate cylinders surrounded by a matrix of polystyrene.

41. The method described in claim 1, wherein the nanofeature array is a uniform periodic array having a uniform lattice spacing between nanofeatures.

42. The method described in claim 1, wherein the nanofeature array has at least two different lattice spacings.

43. The method described in claim 1, further comprising the step of etching an ordered orientation guide recess array comprising a plurality of orientation guide recesses into the substrate prior to applying the catalytic material, such that the structure of the orientation guide array is determined by the polymeric array.

44. The method described in claim 1, wherein the step of etching comprises at least one process selected from the group consisting of metal etching, reactive ion etching, and SiO₂ etching.

45. A nanofeature array made according to the method described in claim 1.

46. The nanofeature array described in claim 45 wherein the nanofeature array is designed to operate as a device selected from the group consisting of filter mediums in electrophoretic separations, high-Q high-frequency nano-scale oscillators, nano-meter scale RF filters, RF signal detectors, analyzers, and field emitter tips.