Polymer solution for nanoimprint lithography to reduce imprint temperature and pressure

• US 20040110856A1
• Filed: 12/04/2002
• Published: 06/10/2004
• Est. Priority Date: 12/04/2002
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Young, Jung Gun, Chen, Yong, Ganapathiappan, Sivapackia, Williams, Richard Stanley
• Granted Patent: US 7,750,059 B2
• Time in Patent Office: Days
• US Class Current: 522/6
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2043/025 forming a microstructure, i.e. fine patterning
• CPC Class Codes: B29C 2059/023 Microembossing
• CPC Class Codes: B29C 35/0888 using transparant moulds
• CPC Class Codes: B29C 43/003 characterised by the choice of material
• CPC Class Codes: B29C 59/022 characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
• 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 40/00 Manufacture or treatment of nanostructures
• 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: G03F 7/033 the binders being polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. vinyl polymers

Abstract

A method of forming features on substrates by imprinting is provided. The method comprises: (a) forming a polymer solution comprising at least one polymer dissolved in at least one polymerizable monomer; and (b) depositing the polymer solution on a substrate to form a liquid film thereon; and then either: (c) curing the liquid film by causing the monomer(s) to polymerize and optionally cross-linking the polymer(s) to thereby form a polymer film, the polymer film having a glass transition temperature (T_g); and imprinting the polymer film with a mold having a desired pattern to form a corresponding negative pattern in the polymer film, or (d) imprinting the liquid film with the mold and curing it to form the polymer film. The temperature of imprinting is as little as 10° C. above the T_g, or even less if the film is in the liquid state. The pressure of the imprinting can be within the range of 100 to 500 psi.

Claims

1. An imprintable polymer solution for imprinting, said polymer solution comprising at least one polymer dissolved in at least one polymerizable monomer.

2. The polymer solution of claim 1 wherein said polymer solution further comprises at least one component selected from the group consisting of at least one initiator, at least one cross-linker, and at least one viscosity modifier.

3. The polymer solution of claim 2 wherein said at least one initiator is selected from the group consisting of (a) thermal curing initiators selected from the group consisting of hydrogen peroxide, benzoyl peroxide, azo compounds selected from the group consisting of 2,2′

-azobisiso-butyronitrile, 4,4′

azobis(cyclohexanecarbonitrile), 4,4′

-azobis(4-cyanovaleric acid) and 2,2′

-azobis(2-methylpropane), t-butyl peroxy-2ethylhexanoate di(t-butylcyclo-hexyl)peroxydicarbonate, dicumyl peroxide, dioctanoyl peroxide, dimyristyl peroxide, dilauroyl peroxide, 1,1-di(1-butylperoxycyclohexane), t-butyl peroxydiethylacetate, and cumyl hydroperoxide, and (b) photoinitiators selected from the group consisting of α

-hydroxy-ketones, α

-amino-ketones, and benzophenones.

4. The polymer solution of claim 2 wherein said at least one cross-linker is selected from molecules that have difunctional polymerizable groups.

5. The polymer solution of claim 4 wherein said at least one cross-linker is selected from the group consisting of ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, tetraethyleneglycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol (PEG) dimethacrylate wherein the polyethylene glycol has a molecular weight from 400 to 6000, tetraethylene glycol dimethacrylate, ethoxylated Bisphenol A dimethacrylate with up to 50 ethoxy units, cyclohexane dimethanol dimethacrylate, tripropylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, alkoxylated glyceryl with up to 30 carbon atoms, trimethylolpropane trimethacrylate, tris(2-hydroxyethyl) isocyanurate trimethacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, mono-2-(methacryloyloxyethyl) maleate, divinyl benzene, methacrylic anhydride, pentaerythritol triallyl ether, di(ethylene glycol) dimethacrylate, di(ethylene glycol) divinyl ether, tetraethylene glycol divinyl ether, di(ethylene glycol) diacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate and mono-2-(methacryloyloxy)ethyl maleate, wherein any methacrylate group can be replaced with an acrylate group or an acrylamide group or a methacrylamide group and wherein the foregoing compounds are either unsubstituted or substituted with at least one group selected from the group consisting of halogen, alkyl, or aryl groups.

6. The polymer solution of claim 1 wherein said at least one polymer has a concentration in said polymer solution of about 0.1 to 50 wt %.

7. The polymer solution of claim 6 wherein said concentration is about 1 to 20 wt %.

8. The polymer solution of claim 7 wherein said concentration is about 5 to 10 wt %.

9. The polymer solution of claim 1 wherein said polymer solution comprises one monomer and one polymer.

10. The polymer solution of claim 9 wherein said monomer is the same as monomer units comprising said polymer.

11. The polymer solution of claim 10 wherein said polymer film is a relatively pure polymer that is substantially uniform in composition.

12. The polymer solution of claim 9 wherein said monomer is different from monomer units comprising said polymer.

13. The polymer solution of claim 1 wherein said at least one polymer is dissolved into any monomer or monomer mixture that said at least one polymer is soluble in.

14. The polymer solution of claim 13 wherein said at least one polymer has a structure selected from the group consisting of:

15. The polymer solution of claim 14 wherein said at least one polymer has a weight average molecular weight within a range of about 5,000 to 3,000,000.

16. The polymer solution of claim 15 wherein said weight average molecular weight is within a range of about 20,000 to 500,000.

17. The polymer solution of claim 16 wherein said weight average molecular weight is within a range of about 50,000 to 200,000.

18. The polymer solution of claim 14 wherein said at least one polymer has a polydispersity within a range of about 1 to 20.

19. The polymer solution of claim 18 wherein said polydisperisity is within a range of about 1 to 5.

20. The polymer solution of claim 19 wherein said polydispersity is within a range of about 1 to 2.

21. The polymer solution of claim 14 wherein said polymer has at least one aromatic pendant group and wherein said polymer is dissolved into its polymerizable monomer.

22. The polymer solution of claim 14 wherein at least one said polymer has polymerizable end-groups that can be substituted for any of said structures and optionally in combination with or without cross-linkers.

23. The polymer solution of claim 22 wherein said polymer is selected from the group consisting of polystyrene with methacrylate terminated, poly(tetrahydrofuran) divinyl ether, poly(ethylene glycol) diacrylate, poly(ethylene glycol) dimethacrylate, poly(propylene glycol) diacrylate, poly(propylene glycol) dimethacrylate, and poly(dimethyl siloxane) with divinyl terminated.

24. The polymer solution of claim 1 wherein said polymerizable monomer is selected from the group consisting of methyl methacrylate, butyl methacrylate, hexyl methacrylate, hexyl acrylate, ethylhexyl methacrylate, ethylhexyl acrylate, octyl acrylate, octyl methacrylate, benzyl methacrylate, benzyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, styrene, α

-methylstyrene, vinyltoluene, chloromethyl styrene, butadiene, vinyl pyrrolidone, vinylyimidazole, allyl alcohol, and vinyl acetate, acrylonitrile, glycidyl methacrylate, ethyl acrylate, ethyl methacrylate, and mixtures thereof.

25. The polymer solution of claim 1 wherein said polymer solution further includes at least one macro monomer with polymerizable end-groups, each containing a polymer.

26. An improved method of forming features on substrates by imprinting, said improved method comprising:

(a) forming a polymer solution comprising at least one polymer dissolved in at least one polymerizable monomer; and

(b) depositing said polymer solution on said substrate to form a liquid film thereon; and

then either;

(c) curing said liquid film by causing said at least one monomer to polymerize and optionally cross-linking said at least one polymer to thereby form a polymer film, said polymer film having a glass transition temperature of less than 100°

C., and imprinting said polymer film with a mold having a desired pattern to form a corresponding negative pattern in said polymer film;

or

(d) imprinting said liquid film with said mold and curing said liquid film in the presence of said mold to form said polymer film with said negative pattern.

27. The method of claim 26 wherein said features have critical dimensions less than 100 nm,

28. The method of claim 27 wherein said systems are selected from the group consisting of nano-electronic circuits, nano-electro-mechanical systems, optical systems including gratings, photonic crystals, optical couplers and devices, and sensors and detectors based on nanometer scale components

29. The method of claim 26 wherein said glass transition temperature is within a range of about 0°

to 100°

C.

30. The method of claim 29 wherein said glass transition temperature is within a range of about 20°

to 70°

C.

31. The method of claim 30 wherein said glass transition temperature is within a range of about 40°

to 60°

C.

32. The method of claim 26 wherein said liquid film is cured by a polymerization process.

33. The method of claim 32 wherein said polymerization process is selected from the group consisting of heating or exposure to UV radiation or both.

34. The method of claim 26 wherein said polymer solution further comprises at least one component selected from the group consisting of at least one initiator, at least one cross-linker, and at least one viscosity modifier.

35. The method of claim 34 wherein said at least one initiator is selected from the group consisting of hydrogen peroxide, benzoyl peroxide, azo compounds selected from the group consisting of (a) thermal curing initiators selected from the group consisting of 2,2′

-azobisiso-butyronitrile, 4,4′

-azobis(cyclohexane-carbonitrile), 4,4′

-azobis(4-cyanovaleric acid) and 2,2′

-azobis(2-methylpropane), t-butyl peroxy-2ethylhexanoate di(t-butylcyclo-hexyl)peroxydicarbonate, dicumyl peroxide, dioctanoyl peroxide, dimyristyl peroxide, dilauroyl peroxide, 1,1-di(t-butylperoxycyclohexane), t-butyl peroxydiethylacetate, and cumyl hydroperoxide, and (b) photoinitiators selected from the group consisting of α

-hydroxy-ketones, α

-amino-ketones, and benzophenones.

36. The method of claim 34 wherein said at least one cross-linker is selected from molecules that have difunctional or polyfunctional polymerizable groups.

37. The method of claim 36 wherein said at least one cross-linker is selected from the group consisting of ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, tetraethyleneglycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol (PEG) dimethacrylate wherein the polyethylene glycol has a molecular weight from 400 to 6000, tetraethylene glycol dimethacrylate, ethoxylated Bisphenol A dimethacrylate with up to 50 ethoxy units, cyclohexane dimethanol dimethacrylate, tripropylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, alkoxylated glyceryl with up to 30 carbon atoms, trimethylolpropane triacrylate, tris(2-hydroxyethyl) isocyanurate trimethacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, mono-2-(methacryloyloxyethyl) maleate, divinyl benzene, methacrylic anhydride, pentaerythritol triallyl ether, di(ethylene glycol) dimethacrylate, di(ethylene glycol) divinyl ether, tetraethylene glycol divinyl ether, di(ethylene glycol) diacrylate, 3-(acryloyloxy)-2-hydroxypropyl methacrylate and mono-2-(methacryloyloxy)ethyl maleate, wherein any methacrylate group can be replaced with an acrylate group or an acrylamide group or a methacrylamide group and wherein the foregoing compounds are either unsubstituted or substituted with at least one group selected from the group consisting of halogen, alkyl, or aryl groups.

38. The method of claim 37 wherein said at least one viscosity modifier is selected from the group consisting of polyethyl oxazoline, polynorbornene, poly alpha-pinenes and poly beta-pinenes, poly(styrene-co-methylstyrene), poly(tetrahydrofuran), poly(vinyl alcohol-co-ethylene), poly(vinyl chloride-co-isobutyl vinyl ether), poly(vinyl chloride-co-vinyl acetate), poly(vinyl phenylketone), poly(vinyl phenol-co-methyl methacrylate), hydroxy ethyl cellulose, grafted polymeric polysaccharide, and styrene-diene polymers.

39. The method of claim 26 wherein said at least one polymer has a concentration in said polymer solution of about 0.1 to 50 wt %.

40. The method of claim 39 wherein said concentration is about 1 to 20 wt %.

41. The method of claim 40 wherein said concentration is about 5 to 10 wt %.

42. The method of claim 26 wherein said polymer solution comprises one monomer and one polymer.

43. The method of claim 42 wherein said monomer is the same as monomer units comprising said polymer.

44. The method of claim 43 wherein said polymer film is a relatively pure polymer that is substantially uniform in composition.

45. The method of claim 42 wherein said monomer is different from monomer units comprising said polymer.

46. The method of claim 45 wherein said polymer film comprises a polymer blend, an interpenetrating network of two polymers, a co-polymer, or a block co-polymer.

47. The method of claim 26 wherein said at least one polymer is dissolved into any monomer that said polymer is soluble in.

48. The method of claim 47 wherein said at least one polymer has a structure selected from the group consisting of:

49. The method of claim 48 wherein said at least one polymer has a weight average molecular weight within a range of about 5,000 to 3,000,000.

50. The method of claim 49 wherein said weight average molecular weight is within a range of about 20,000 to 500,000.

51. The method of claim 50 wherein said weight average molecular weight is within a range of about 50,000 to 200,000.

52. The method of claim 48 wherein said at least one polymer has a polydispersity within a range of about 1 to 20.

53. The method of claim 52 wherein said polydisperisity is within a range of about 1 to 5.

54. The method of claim 53 wherein said polydispersity is within a range of about 1 to 2.

55. The method of claim 48 wherein said at least one polymer has at least one aromatic pendant group and wherein said polymer is dissolved into its polymerizable monomer.

56. The method of claim 48 wherein at least one said polymer has polymerizable end-groups that can be substituted for any of said structures and optionally in combination with or without cross-linkers.

57. The method of claim 56 wherein said polymer is selected from the group consisting of polystyrene with methacrylate terminated, poly(tetrahydrofuran) divinyl ether, poly(ethylene glycol) diacrylate, poly(ethylene glycol) dimethacrylate, poly(propylene glycol) diacrylate, poly(propylene glycol) dimethacrylate, and poly(dimethyl siloxane) with divinyl terminated.

58. The method of claim 26 wherein said polymerizable monomer is selected from the group consisting of methyl methacrylate, butyl methacrylate, hexyl methacrylate, hexyl acrylate, ethylhexyl methacrylate, ethylhexyl acrylate, octyl acrylate, octyl methacrylate, benzyl methacrylate, benzyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, styrene, α

-methylstyrene, vinyltoluene, chloromethyl styrene, butadiene, vinyl pyrrolidone, vinyl imidazole, allyl alcohol, and vinyl acetate, acrylonitrile, glycidyl methacrylate, ethyl acrylate, ethyl methacrylate, and mixtures thereof.

59. The method of claim 26 wherein said solution further includes at least one macro monomer with polymerizable end-groups, each containing a polymer.

60. The method of claim 26 wherein said imprinting is performed at a process temperature that is higher than said glass transition temperature for said solid polymer film in step (c) or even less for said liquid film in step (d) and at a pressure of about 100 to 500 psi.

61. The method of claim 60 wherein said process temperature is as little as 10°

C. higher than said glass transition temperature for said solid polymer film in step (c).

62. The method of claim 26 wherein said imprinting comprises compression molding, followed by a pattern transfer process.

63. The method of claim 62 wherein following said imprinting, said mold is removed and an anisotropic etching process is used to transfer said pattern into the entire polymer film thickness by removing polymer film remaining in compressed areas.