Insulators for high density circuits

• US 20020168872A1
• Filed: 06/24/2002
• Published: 11/14/2002
• Est. Priority Date: 08/25/1999
• Status: Active Grant

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Farrar, Paul A.
• Granted Patent: US 6,872,671 B2
• Time in Patent Office: Days
• US Class Current: 438/780
• CPC Class Codes: H01L 21/02118 carbon based polymeric organic or inorganic material, e.g. polyimides, poly cyclobutene or PVC polymers per se C08G, photoresist per se G03F
• CPC Class Codes: H01L 21/02126 the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
• CPC Class Codes: H01L 21/02282 liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/3105 After-treatment
• CPC Class Codes: H01L 21/31058 of organic layers
• CPC Class Codes: H01L 21/312 Organic layers, e.g. photoresist H01L21/3105, H01L21/32 take precedence; photoresists per se G03C
• CPC Class Codes: H01L 21/321 After treatment
• CPC Class Codes: H01L 21/7682 the dielectric comprising air gaps
• CPC Class Codes: H01L 23/5329 Insulating materials
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 1/024 Dielectric details, e.g. changing the dielectric material around a transmission line
• CPC Class Codes: H05K 1/0346 containing N

Abstract

A conductive system and a method of forming an insulator for use in the conductive system is disclosed. The conductive system comprises a foamed polymer layer on a substrate. The foamed polymer layer has a surface that is hydrophobic, and a plurality of conductive structures are embedded in the foamed polymer layer. An insulator is formed by forming a polymer layer having a thickness on a substrate. The polymer layer is foamed to form a foamed polymer layer having a surface and a foamed polymer layer thickness, which is greater than the polymer layer thickness. The surface of the foamed polymer layer is treated to make the surface hydrophobic.

Claims

1. A method of forming an insulator comprising:

forming a material layer having a material layer thickness on a substrate;

foaming the material layer to form a foamed material layer having a surface and a foamed thickness, the foamed thickness being greater than the material layer thickness; and

treating the surface to make the surface hydrophobic.

2. The method of claim 1, wherein forming a material layer having a thickness on a substrate comprises:

forming a polymer layer on the substrate.

3. The method of claim 1, wherein forming a material layer having a thickness on a substrate comprises:

applying an aerogel to the substrate;

spinning the substrate; and

curing the aerogel such that, after curing, the thickness is between about 0.6 microns and about 0.8 microns.

4. A method of forming an insulator comprising:

forming a polymer layer on a substrate;

foaming the polymer layer to form a foamed polymer layer having a surface and a foamed polymer dielectric constant between about 0.8 and about 1.0; and

treating the surface to make the surface hydrophobic.

5. The method of claim 4, wherein forming a polymer layer on a substrate comprises:

depositing polyimide containing silane on the substrate.

6. The method of claim 4, wherein foaming the polymer layer to form a foamed polymer layer having a surface and a foamed polymer dielectric constant between about 0.8 and 1.0 comprises:

forming a foamed polymer layer having a depth of between about 1.8 and 2.0 microns.

7. The method of claim 4, wherein treating the surface to make the surface hydrophobic comprises:

flowing methane radicals over the surface.

8. A method of forming an insulator comprising:

forming a polymer layer on a substrate;

foaming the polymer layer with a supercritical fluid to form a foamed polymer layer having a surface and a foamed polymer dielectric constant between about 0.8 and 1.0; and

treating the surface to make the surface hydrophobic.

9. The method of claim 8, wherein forming a polymer layer on a substrate comprises:

forming a polyimide layer on the substrate.

22. The method of claim 8, wherein foaming the polymer layer with a supercritical fluid includes exposing the polymer layer to a CO₂ supercritical fluid.

23. The method of claim 8, wherein foaming the polymer layer with a supercritical fluid includes exposing the polymer layer to a supercritical fluid with a critical pressure below about 100 atmospheres and a critical temperature of about room temperature.

24. The method of claim 8, wherein foaming the polymer layer with a supercritical fluid includes exposing the polymer layer to a supercritical fluid that is nontoxic and nonflammable.

25. The method of claim 8, wherein foaming the polymer layer with a supercritical fluid includes exposing the polymer layer to a supercritical fluid selected from a group comprising NH₃, NR₃, ROH, H₂O, CO₂, N₂O, He, Ne, Ar, HF, HCl, HBr, BCl₃, Cl₂, F₂, O₂, N₂, CH₄, C₂H₆, C₃H₈, C₂H₄, CO(OCH₃)₂, CF₄, C₂F₄, CH₃F, and C₅H₂F₆O₂.

26. The method of claim 8, wherein the method further includes depressurizing after exposing the polymer layer to the supercritical fluid at a rate such that the polymer layer converts to the foamed polymer layer before substantial diffusion of the supercritical fluid out of the polymer layer occurs.

10. A method of forming an insulator comprising:

forming a polymer layer having a thickness on a substrate from a polymer having a silane additive;

foaming the polymer layer to form a foamed polymer layer having a surface and a foamed polymer layer thickness, the foamed polymer layer thickness is greater than the polymer layer thickness by a factor of about between about 2.8 and 3.2; and

treating the surface to make the surface hydrophobic.

27. The method of claim 10, wherein forming a polymer layer includes forming a layer of parylene containing silane followed by a low temperature bake.

28. The method of claim 10, wherein the method further includes curing the polymer layer before foaming the polymer layer.

11. A method of forming an insulator comprising:

forming a polymer layer having a thickness on a substrate from a polymer having a silane additive;

foaming the polymer layer to form a foamed polymer layer having a surface and a foamed polymer layer thickness, the foamed polymer layer thickness is greater than the polymer layer thickness; and

exposing the surface to a gas.

12. The method of claim 11, wherein exposing the surface to a gas comprises:

exposing the surface to methane.

13. The method of claim 11, wherein exposing the surface to a gas comprises:

passing a methane gas through a plasma to form a plurality of methane radicals; and

exposing the surface to at least some of the plurality of methane radicals.

16. The method of claim 15, wherein forming an aerogel layer having a surface on a substrate comprises:

forming an aerogel layer having a cell size of less than one micron.

17. The method of claim 15, wherein forming an aerogel layer having a surface on a substrate comprises:

forming an aerogel layer having a cell size of less than one-tenth micron.

18. The method of claim 15, wherein treating the surface to make the surface hydrophobic comprises:

exposing the surface to methane radicals.

19. The method of claim 15, wherein treating the surface to make the surface hydrophobic comprises:

forming a plurality of methane radicals using a high frequency electric field; and

exposing the surface to at least some of the plurality of methane radicals.

29. The method of claim 14, wherein exposing the surface to a gas includes exposing the surface to methane.

30. The method of claim 14, wherein exposing the surface to a gas includes:

passing a methane gas through a plasma to form a plurality of methane radicals; and

exposing the surface to at least some of the plurality of methane radicals.

14. A method of forming an insulator comprising:

forming a polymer layer having a thickness on a substrate from a polymer having a silane additive;

foaming the polymer layer to form a foamed polymer layer having a surface, a cell size, and a foamed polymer layer thickness, the foamed polymer layer thickness is greater than the polymer layer thickness, and the cell size is less than about one-tenth of a micron; and

exposing the surface to a gas.

15. A method of forming an insulator comprising:

forming an aerogel layer on a substrate, the aerogel layer having a surface; and

treating the surface to make the surface hydrophobic.

20. A method of forming an insulator comprising:

forming an air-bridge structure having a surface on a substrate; and

treating the air-bridge structure to make the surface hydrophobic.

21. The method of claim 20, wherein treating the surface to make the surface hydrophobic comprises:

forming a plurality of methane radicals using a high frequency electric field; and

exposing the surface to at least some of the plurality of methane radicals.

31. The method of claim 20, wherein treating the surface to make the surface hydrophobic includes:

passing methane gas through a plasma forming a plurality of methane radicals; and

exposing the surface to at least some of the plurality of methane radicals.

32. A method of forming a conductive structure comprising:

forming a material layer having a material layer thickness on a substrate;

foaming the material layer to form a foamed material layer having a surface and a foamed thickness, the foamed thickness being greater than the material layer thickness;

treating the surface to make the surface hydrophobic;

forming channels in the foamed material layer; and

filling the channels with a metal.

33. The method of claim 32, wherein filling the channels with a metal includes filling the channels with a metal selected from a group consisting of silver, aluminum, gold, copper, tungsten, and alloys of silver, aluminum, gold, copper, and tungsten.

34. The method of claim 32, wherein forming channels in the foamed material layer includes:

applying a photoresist to the surface of the foamed material layer;

forming patterns for the channels in the photoresist; and

etching the photoresist.

36. The method of claim 35, wherein foaming the polymer layer includes forming a foamed polymer layer having a thickness of between about 1.8 and 2.0 microns.

37. The method of claim 35, wherein foaming the polymer layer includes forming a foamed polymer layer of polyimide containing silane.

38. The method of claim 37, wherein the method further includes curing a layer of polyimide containing silane before foaming the layer of polyimide containing silane.

40. The method of claim 39, wherein forming an aerogel layer includes applying an aerogel to the substrate;

spinning the substrate; and

curing the aerogel.

41. The method of claim 39, wherein filling the channels with a metal includes filling the channels with a metal selected from a group consisting of silver, aluminum, gold, copper, tungsten, and alloys of silver, aluminum, gold, copper, and tungsten.

42. The method of claim 39, wherein forming channels in the foamed material layer includes:

applying a photoresist to the surface of the foamed material layer;

forming patterns for the channels in the photoresist; and

etching the photoresist.

35. A method of forming a conductive structure comprising:

forming a polymer layer having a thickness on a substrate, the polymer layer having a silane additive;

foaming the polymer layer to form a foamed polymer layer having a surface and a foamed polymer layer thickness, the foamed polymer layer thickness greater than the polymer layer thickness;

exposing the surface to a gas;

forming channels in the foamed material layer; and

filling the channels with a metal.

39. A method of forming a conductive structure comprising:

forming an aerogel layer on a substrate, the aerogel layer having a surface;

treating the surface to make the surface hydrophobic;

forming channels in the foamed material layer; and

filling the channels with a metal.

43. A method of forming a conductive structure comprising:

forming an air-bridge structure having a surface on a substrate; and

treating the air-bridge structure to make the surface hydrophobic.

44. The method of claim 43, wherein treating the surface to make the surface hydrophobic comprises:

forming a plurality of methane radicals using a high frequency electric field; and

exposing the surface to at least some of the plurality of methane radicals.

45. The method of claim 43, wherein forming an air-bridge structure includes fabricating the air-bridge structure using a metal selected from a group consisting of silver, aluminum, gold, copper, tungsten, and alloys of silver, aluminum, gold, copper, and tungsten.

46. The method of claim 43, wherein treating the surface to make the surface hydrophobic comprises:

passing methane gas through a plasma forming a plurality of methane radicals; and

exposing the surface to at least some of the plurality of methane radicals.