Fabrication of ceramic microstructures from polymer compositions containing ceramic nanoparticles

• US 6,245,849 B1
• Filed: 06/02/1999
• Issued: 06/12/2001
• Est. Priority Date: 06/02/1999
• Status: Expired due to Term

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Chinn, Douglas, Zhang, Z. John, Morales, Alfredo Martin
• Primary Examiner(s): Cain, Edward J.
• Application Number:
  US09/325,003
• Time in Patent Office: 741 Days
• Field of Search: 524/442, 524/443, 524/444, 524/445, 524/447, 524/448, 524/450
• US Class Current: 524/442
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 1/056 Submicron particles having a size above 100 nm up to 300 nm
• CPC Class Codes: B22F 2003/1046 with separating means for articles to be sintered
• CPC Class Codes: B22F 3/1275 by coating a model and eliminating the model before consolidation
• CPC Class Codes: B28B 1/14 by simple casting, the material being neither forcibly fed nor positively compacted for molten material B28B1/54
• CPC Class Codes: B28B 7/342 which are at least partially destroyed, e.g. broken, molten, before demoulding; Moulding surfaces or spaces shaped by, or in, the ground, or sand or soil, whether bound or not; Cores consisting at least mainly of sand or soil, whether bound or not
• 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 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: C04B 35/111 Fine ceramics
• CPC Class Codes: C04B 35/2658 Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites
• CPC Class Codes: C04B 35/622 Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
• CPC Class Codes: G03F 7/00 Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor using photoresist structures for special production processes, see the relevant places, e.g. B44C, H01L, e.g. H01L21/00, H05K
• CPC Class Codes: G03F 7/0002 Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping
• CPC Class Codes: Y10S 977/777 Metallic powder or flake
• CPC Class Codes: Y10S 977/887 Nanoimprint lithography, i.e. nanostamp
• CPC Class Codes: Y10S 977/888 Shaping or removal of materials, e.g. etching
• CPC Class Codes: Y10S 977/893 Deposition in pores, molding, with subsequent removal of mold

Abstract

A method is provided for fabricating ceramic microstructures, i.e., microcomponents of micron or submicron dimensions. A polymer composition is prepared containing a polymer, typically a thermally or chemically curable polymer, and nanometer size (1 to 1000 nm in diameter) ceramic particles. A mold, such as a lithographically patterned mold, preferably a LIGA mold, is filled with the polymer composition and the polymer is then cured or otherwise hardened. The elevated segments of the mold are then removed. The surface-attached ceramic microstructures so provided may then be removed from the substrate and, if desired, pyrolyzed and sintered.

Claims

1. A method for preparing ceramic microstructures, comprising:

(a) providing, as a mold, a substrate having a pattern on its surface, said pattern comprised of chemically removable elevated segments and corresponding voids therebetween;

(b) applying a curable polymer composition to the substrate surface and pressing the composition into the voids of the surface pattern, said curable polymer composition comprising ceramic nanoparticles and a curable binder polymer; and

(c) curing the polymer to provide ceramic microstructures in said voids.

2. The method of claim 1, wherein the curable binder polymer is selected from the group consisting of vinyl polymers, acrylic polymers, silicon-containing polymers, epoxy resins, and copolymers and blends thereof.

3. The method of claim 1, wherein the polymer is a thermally curable polymer and step (c) is conducted by heating the composition to a temperature sufficient to cure the polymer.

4. The method of claim 1, wherein the polymer is a chemically curable polymer, and the curable polymer composition additionally includes a curing agent.

5. The method of claim 4, wherein the chemically curable polymer is an epoxy resin.

6. The method of claim 1, wherein the polymer is a photolytically curable polymer, and step (c) is conducted by irradiating the polymer composition.

7. The method of claim 1, wherein step (c) is conducted by irradiating the polymer composition with an electron beam.

8. The method of claim 1, further including, prior to step (b), treating the substrate surface to facilitate removal of a material deposited thereon.

9. The method of claim 8, wherein the surface treatment comprises polishing.

10. The method of claim 8, wherein the surface treatment comprises deposition of a low adhesion coating comprised of a material-releasing agent.

11. The method of claim 10, wherein the material-releasing agent is selected from the group consisting of poly(tetrafluoroethylene), silicones and waxes.

12. The method of claim 11, wherein the material-releasing agent is poly(tetrafluoroethylene).

13. The method of claim 8, wherein the surface treatment comprises deposition of a chemically removable release layer.

14. The method of claim 13, wherein the release layer is comprised of poly(methyl methacrylate).

15. The method of claim 1, further including:

(d) removing the elevated segments to provide said ceramic microstructures on the substrate surface.

16. The method of claim 15, further including:

(e) removing the ceramic microstructures from the substrate surface.

17. The method of claim 15, further comprising pyrolyzing the ceramic microstructures by heating to a temperature effective to remove organic material contained therein and to convert any inorganic material present to ceramic material.

18. The method of claim 16, further comprising pyrolyzing the ceramic microstructures by heating to a temperature effective to remove organic material contained therein and to convert any inorganic material present to ceramic material.

19. The method of claim 17, wherein pyrolyzing is conducted at a temperature in the range of about 300°

to 700°

.

20. The method of claim 19, wherein pyrolyzing is conducted at a temperature in the range of about 400°

C. to 600°

C.

21. The method of claim 18, wherein pyrolyzing is conducted at a temperature in the range of about 300°

C. to 700°

C.

22. The method of claim 21, wherein pyrolyzing is conducted at a temperature in the range of about 400°

C. to 600°

C.

23. The method of claim 1, wherein the ceramic nanoparticles are in the range of approximately 1 to 1000 nanometers in diameter.

24. The method of claim 23, wherein the ceramic nanoparticles are in the range of approximately 1 to 500 nanometers in diameter.

25. The method of claim 24, wherein the ceramic nanoparticles are in the range of approximately 1 to 100 nanometers in diameter.

26. The method of claim 1, wherein the ceramic nanoparticles are comprised of a metal oxide.

27. The method of claim 26, wherein the metal oxide is selected from the group consisting of Al₂O₃, ZrO₂, TiO₂, ZnO, SiO₂, BaTiO₃, SrTiO₃, WO₂, WO₃, Fe₂O₃, Fe₃O₄, Ca₅(PO₄)OH, MnFe₂O₄, PbZr0.5Ti_0.5O₃, BaFe₁₂O₁₉, CrO₂, Cr₂O₃, MoO₂ and MoO₃.

28. The method of claim 1, wherein the ceramic nanoparticles are comprised of SiC, Si₃N₄ or Si₂ON₂.

29. The method of claim 1, wherein the ceramic nanoparticles are comprised of aluminum nitride, tungsten carbide, barium samarium cobalt, neodymium iron boride, TiN, TiC, MoSe₂, MoSe₃, MoS₂ or MoS₃.

30. The method of claim 1, wherein the mold used in part (a) is a lithographically patterned mold and the voids of the surface pattern are less than about 100 microns in diameter, so that the resulting ceramic microstructures are less than about 100 microns in diameter.

31. The method of claim 30, wherein the mold is a LIGA mold.

32. The method of claim 30, wherein the aspect ratio of the ceramic microstructure is greater than about 20:

1.

33. The method of claim 32, wherein the aspect ratio of the ceramic microstructure is greater than about 40:

1.

34. The method of claim 1, wherein the curable polymer composition further comprises a solvent for the curable binder polymer.

35. The method of claim 34, wherein the solvent is water or a lower alkanol.

36. The method of claim 34, wherein the ceramic nanoparticles represent approximately 5 wt. % to 95 wt. % of the curable polymer composition.

37. The method of claim 36, wherein the curable polymer represents approximately 5 wt. % to 30 wt. % of the curable polymer composition.

38. The method of claim 1, wherein the elevated segments are comprised of a photoresist material.

39. The method of claim 38, wherein the photoresist material is poly(methyl methacrylate).

40. The method of claim 1, wherein the substrate is comprised of metallized silicon.

41. The method of claim 1, further comprising, following step (b) and prior to step (c), planarizing the substrate surface to remove excess polymer composition.

52. A ceramic microstructure prepared by the process of claim 17.

53. A ceramic microstructure prepared by the process of claim 18.

42. A method for preparing ceramic microstructures, comprising:

(a) providing a lithographically patterned mold comprising a substrate having a pattern on its surface, said pattern comprised of chemically removable elevated segments and corresponding voids therebetween, said voids having a diameter of less than about 100 microns in diameter;

(b) applying a curable polymer composition to the substrate surface and pressing the composition into the voids of the surface pattern, said curable polymer composition comprising a paste of ceramic nanoparticles having a diameter in the range of approximately 1 nm to 1000 nm, a curable binder polymer selected from the group consisting of vinyl polymers, acrylic polymers, silicon-containing polymers, epoxy resins, and copolymers and blends thereof, and a solvent for the curable binder polymer, wherein the ceramic nanoparticles represent approximately 15 wt. % to 95 wt. % of the composition and the curable polymer represents approximately 5 wt. % to 30 wt. % of the composition;

(c) curing the polymer to provide ceramic microstructures in said voids; and

(d) removing the elevated segments to provide said ceramic microstructures on the substrate surface.

43. A method for preparing ceramic microstructures permanently affixed to a substrate, comprising:

(a) providing a substrate having a substantially planar surface and a recess therein extending from the substrate surface into the substrate interior, wherein the recess is shaped such that the width of the recess at the substrate surface is smaller than the width of the recess in the substrate interior;

(b) applying a curable polymer composition to the substrate surface and pressing the composition into the recess, said polymer composition comprising a curable binder polymer, ceramic nanoparticles and a solvent for the binder polymer, while allowing a portion of the composition to remain on the substrate surface above the recess; and

(c) curing the binder polymer to provide a ceramic microstructure having a first segment in said recess and conforming in shape thereto, and a second segment above the substrate surface.

44. The method of claim 43, wherein the portion of the composition allowed to remain on the substrate surface in step (b) has a shape defined by chemically removable elevated segments on the substrate.

45. A method for preparing ceramic microstructures, comprising:

(a) providing, as a mold, a substrate having a pattern on its surface, said pattern comprised of chemically removable elevated segments and corresponding voids therebetween;

(b) forming a paste of a binder polymer, ceramic nanoparticles, and a solvent for said polymer;

(c) applying the paste to the substrate surface and pressing the paste into the voids of the surface pattern; and

(c) removing the solvent to provide ceramic microstructures in said voids.

46. A ceramic microstructure comprising a compressed solid of:

a matrix of a cured polymer; and

ceramic nanoparticles dispersed throughout the matrix, wherein the aspect ratio of the microstructure is greater than about 20;

1.

47. The ceramic microstructure of claim 46, wherein the aspect ratio of the microstructure is greater than about 40:

1.

48. The ceramic microstructure of claim 46, wherein the ceramic nanoparticles are comprised of a metal oxide.

49. The ceramic microstructure of claim 48, wherein the metal oxide is selected from the group consisting of metal oxide is selected from the group consisting of Al₂O₃, ZrO₂, TiO₂, ZnO, SiO₂, BaTiO₃, SrTiO₃, WO₂, WO₃, Fe₂O₃, Fe₃O₄, Ca₅(PO₄)OH, MnFe₂O₄, PbZr_0.5Ti_0.5O₃, BaFe₁₂O₁₉, CrO₂, Cr₂O₃, MoO₂ and MoO₃.

50. The ceramic microstructure of claim 46, wherein the ceramic nanoparticles are comprised of SiC, Si₃N₄ or Si₂ON₂.

51. The ceramic microstructure of claim 46, wherein the ceramic nanoparticles are comprised of aluminum nitride, tungsten carbide, barium samarium cobalt, neodymium iron boride, TiC, TiN, MoSe₂, MoSe₃, MoS₂ or MoS₃.