AIR GAP INTERCONNECTS USING CARBON-BASED FILMS

• US 20100093168A1
• Filed: 10/10/2008
• Published: 04/15/2010
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: NAIK, MEHUL
• Granted Patent: US 7,928,003 B2
• Time in Patent Office: Days
• US Class Current: 438/618
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/76807 for dual damascene structures
• CPC Class Codes: H01L 21/76811 involving multiple stacked pre-patterned masks
• CPC Class Codes: H01L 21/76813 involving a partial via etch
• CPC Class Codes: H01L 21/76816 Aspects relating to the layout of the pattern or to the size of vias or trenches layout of the interconnections per se H01L23/528; CAD of ICs G06F30/00
• CPC Class Codes: H01L 21/7682 the dielectric comprising air gaps
• CPC Class Codes: H01L 21/76834 formation of thin insulating films on the sidewalls or on top of conductors H01L21/76831 takes precedence
• CPC Class Codes: H01L 21/76837 Filling up the space between adjacent conductive structures; Gap-filling properties of dielectrics
• CPC Class Codes: H01L 21/76885 By forming conductive members before deposition of protective insulating material, e.g. pillars, studs

Abstract

A method of forming an interconnect structure comprising: forming a sacrificial inter-metal dielectric (IMD) layer over a substrate, wherein the sacrificial IMD layer comprising a carbon-based film, such as amorphous carbon, advanced patterning films, porous carbon, or any combination thereof; forming a plurality of metal interconnect lines within the sacrificial IMD layer; removing the sacrificial IMD layer, with an oxygen based reactive process; and depositing a non-conformal dielectric layer to form air gaps between the plurality of metal interconnect lines. The metal interconnect lines may comprise copper, aluminum, tantalum, tungsten, titanium, tantalum nitride, titanium nitride, tungsten nitride, or any combination thereof. Carbon-based films and patterned photoresist layers may be simultaneously removed with the same reactive process. Highly reactive hydrogen radicals processes may be used to remove the carbon-based film and simultaneously pre-clean the metal interconnect lines prior to the deposition of a conformal metal barrier liner.

Claims

1. A method of forming an interconnect structure comprising:

forming a sacrificial inter-metal dielectric (IMD) layer over a substrate, wherein the sacrificial IMD layer comprising a carbon-based film;

forming a plurality of metal interconnect lines within the sacrificial IMD layer;

removing the sacrificial IMD layer; and

depositing a non-conformal dielectric layer to form air gaps between the plurality of metal interconnect lines.

2. The method of claim 1, wherein the carbon-based film comprises a carbon-based material selected from the group consisting of:

amorphous carbon, advanced patterning films, porous carbon, and any combination thereof.

3. The method of claim 1, wherein the removal of all or part of the carbon-based film comprises a reactive process having oxygen based chemistries.

4. The method of claim 3, further comprises depositing and patterning a photoresist layer used in the forming of the said interconnect structure, and wherein the reactive process for removing all or part of the carbon-based film is also used for the simultaneous removal of the patterned photoresist layer.

5. The method of claim 3, wherein the reactive process comprises a plasma generated from a source gas comprising a gas selected from the group consisting of:

ozone, oxygen, ammonia, hydrogen, and any combination thereof.

6. The method of claim 1, wherein the removal of all or part of the carbon-based film comprises a highly reactive hydrogen radicals process.

7. The method of claim 6, further comprises depositing a conformal metal barrier liner on the plurality of interconnect lines prior to the deposition of the non-conformal dielectric layer, and wherein the highly reactive hydrogen radicals process is used to remove all or part of the carbon-based film and to pre-clean the surface of the metal interconnect lines prior to the deposition of the conformal metal barrier liner, wherein the removal and pre-clean processes are combined into a single process on a single piece of equipment.

8. The method of claim 1, wherein the metal interconnect lines comprise a metal and/or conductive compound selected from the group consisting of:

copper, aluminum, tantalum, tungsten, titanium, tantalum nitride, titanium nitride, tungsten nitride, and any combination thereof.

9. The method of claim 1, wherein the metal interconnect lines comprise copper.

47. The method of claim 1, further comprising:

depositing a non-carbon-based film over the carbon-based film;

fully patterning the non-carbon-based film; and

transferring the fully patterned non-carbon-based film to the carbon-based film, wherein the fully patterned carbon-based film is used for forming the plurality of metal interconnect lines within the sacrificial IMD layer.

48. The method of claim 47, wherein the fully patterning of the non-carbon-based film comprises a double patterning method, which comprises patterning with two or more masks having relaxed pitches between alternating interconnect structures onto the non-carbon-based film, wherein the interconnect structures on each mask are different and offset in position from the interconnect structures on the other masks, and wherein the patterning with the two or more masks comprises aligning the offsetting masks so that the interconnect structures formed from a subsequent mask are positioned in the regions between the interconnect structures formed from a preceding mask.

49. The method of claim 47, wherein the fully patterning of the non-carbon-based film comprises:

blanket depositing and patterning a first patterned photoresist layer, wherein the patterning of the first patterned photoresist layer comprises an exposure of a first pattern onto the photoresist; and

then developing the exposed photoresist to form the first pattern photoresist layer;

performing a resist freeze of the first patterned photoresist layer, so as to stabilize the first patterned photoresist;

exposing the first patterned photoresist layer with a second mask;

developing the first patterned photoresist layer exposed with the second mask to form a fully patterned photoresist layer; and

transferring the fully patterned photoresist layer to the non-carbon-based film to form the fully patterned non-carbon-based film.

50. The method of claim 47, wherein the fully patterning of the non-carbon-based film comprises:

blanket depositing a hard mask layer;

blanket depositing and patterning a first patterned photoresist layer, wherein the patterning of the first patterned photoresist layer comprises an exposure of a first pattern having a first plurality of interconnect structure patterns onto a first photoresist; and

then developing of the first photoresist to form the first pattern photoresist layer;

transferring the first pattern into a hard mask layer to form a first patterned hard mask layer;

removing the first patterned photoresist layer,

blanket depositing and patterning a second patterned photoresist layer, wherein the patterning of the second patterned photoresist layer comprises an exposure of a second pattern onto a second photoresist layer with a second mask having a plurality of second interconnect structure patterns positioned between the first plurality of interconnect structure patterns formed in the first hard mask layer; and

then developing the second photoresist layer exposed with the second mask to form the second pattern photoresist layer;

transferring the second pattern of the second patterned photoresist layer to the first patterned hard mask layer to form a fully patterned hard mask layer; and

transferring the fully patterned hard mask layer to the non-carbon based layer to form the fully patterned non-carbon based film.

10. A method of forming an interconnect structure comprising:

providing a substrate on which to form the interconnect structure;

blanket depositing a carbon-based film over the substrate;

blanket depositing a non-carbon-based film over the carbon-based film;

blanket depositing a layer of photoresist over the non-carbon-based film;

patterning the photoresist layer;

transferring the patterned photoresist layer onto the non-carbon-based film;

transferring the patterned non-carbon-based film to the carbon-based film;

removing the patterned photoresist layer;

blanket depositing a metal conductor layer;

planarizing the metal conductor layer;

removing the patterned carbon-based film; and

blanket depositing a non-conformal dielectric layer, wherein the non-conformal dielectric layer forms air gaps in regions between the planarized metal conductors.

11. The method of claim 10, wherein the removing of the patterned photoresist layer and the patterning of the carbon-based film are performed substantially simultaneously.

12. The method of claim 10, wherein the method of removing the patterned photoresist layer and the method of removing part of the carbon-based material to form the patterned carbon-based film, comprise substantially the same method of removing.

13. The method of claim 10, further comprising blanket depositing a conformal metal barrier liner on the planarized metal conductors, after removing the patterned carbon-based film and before depositing the non-conformal dielectric layer.

14. The method of claim 13, wherein the removal of the patterned carbon-based film comprises a highly reactive hydrogen radicals process, wherein the highly reactive hydrogen radicals process is also used to pre-clean the surface of the planarized metal conductors prior to the deposition of the conformal metal barrier liner, and wherein the removal and pre-clean processes are combined into a single process on a single piece of equipment.

15. The method of claim 13, wherein the metal barrier liner comprises a material selected from the group consisting of silicon carbide, amorphous silicon carbide, silicon nitride, silicon oxide, and any combination thereof.

16. The method of claim 13, wherein the metal barrier liner comprises a BLOk™

layer, wherein the BLOk™

layer comprises amorphous silicon carbide having a lower dielectric constant than silicon carbide.

17. The method of claim 10, further comprising planarizing the non-conformal dielectric layer having air gaps in the regions between the metal conductors, wherein the air gaps are completely engulfed within the planarized non-conformal dielectric layer, wherein the air gaps in the regions between the planarized metal conductors reduces the capacitive coupling between the planarized metal conductors.

18. The method of claim 10, wherein the metal conductor layer comprises a metal and/or conductive compound selected from the group consisting of:

copper, aluminum, tantalum, tungsten, titanium, tantalum nitride, titanium nitride, tungsten nitride, and any combination thereof.

19. The method of claim 10, wherein the metal conductor layer comprises copper.

20. The method of claim 10, wherein the process to deposit the non-conformal dielectric layer comprises a chemical vapor deposition (CVD) process.

21. The method of claim 10, wherein the non-conformal dielectric layer comprises a tetra-ethyl ortho silicate (TEOS) oxide.

22. The method of claim 10, wherein the non-carbon-based film comprises a dielectric anti-reflective coating (DARC) layer.

23. The method of claim 10, wherein the non-carbon-based film comprises a hard mask, wherein the hard mask comprises a material selected from the group consisting of silicon nitride, poly silicon, silicon dioxide, amorphous silicon, boron nitride, and any combination thereof.

24. The method of claim 10, wherein the carbon-based film comprises an amorphous carbon film and/or an advanced patterning film (APF™

).

25. The method of claim 10, further comprising a metal siliciding process to form a metal suicide layer on an exposed metal surface on the top of the planarized metal conductor, wherein the metal siliciding process is performed prior to removing the patterned carbon-based film.

26. The method of claim 25, wherein the metal siliciding process comprises a SiH₄ soak followed by a NH₃ plasma treatment of the exposed metal surface.

27. The method of claim 10, further comprising a selective metal deposition to form a selective metal cap on an exposed metal surface on the top of the planarized metal conductor, wherein the selective metal deposition is performed prior to removing the patterned carbon-based film.

28. The method of claim 27, wherein the selective metal cap comprises W and/or CoWP materials.

29. A method of forming an interconnect structure comprising:

providing a substrate having an air gap area and an exclusion area;

blanket depositing a first carbon-based film over the substrate;

blanket depositing a non-carbon-based film over the first carbon-based film;

blanket depositing and patterning an interconnect photoresist layer with an interconnect pattern;

transferring the interconnect pattern to the non-carbon-based film;

transferring the interconnect pattern to the first carbon-based film;

removing the patterned interconnect photoresist layer;

blanket depositing and planarizing a metal layer to form a plurality of planarized metal interconnect lines;

blanket depositing a first barrier layer;

blanket depositing and patterning an exclusion photoresist layer to protect the exclusion area;

removing the first barrier layer from the air gap area;

removing the patterned exclusion photoresist layer from the exclusion area and removing the patterned first carbon-based film from the air gap area; and

blanket depositing a non-conformal dielectric layer to form air gaps in the air gap area, wherein the air gaps are positioned between the planarized metal interconnect lines.

30. The method of claim 29, further comprising blanket depositing a first metal barrier liner, wherein the first metal barrier liner is deposited before the deposition of the non-conformal dielectric layer.

31. The method of claim 29, wherein the removing of the patterned interconnect photoresist layer and the transferring of the interconnect pattern into the first carbon-based film are both performed substantially simultaneously, with substantially the same method of removing both photoresist material and carbon-based film material.

32. The method of claim 29, wherein removing the patterned exclusion photoresist layer from the exclusion area and removing the first patterned carbon-based film from the air gap area occur substantially simultaneously, with substantially the same method of removing both photoresist material and carbon-based film material.

33. The method of claim 29, further comprising:

planarizing the non-conformal dielectric layer, wherein in the air gap area the air gaps are engulfed in the planarized non-conformal dielectric, and wherein planarizing the non-conformal dielectric layer in the exclusion area removes at least part of the non-conformal dielectric from the exclusion area; and

wherein the first carbon-based film comprises an organic low-k dielectric material.

34. The method of claim 33, wherein the organic low-k dielectric material has good electrical isolation properties and is suitable for permanently isolating the planarized metal interconnect lines for the life of the interconnect structure.

35. The method of claim 29, further comprising:

planarizing the substrate after the deposition of the non-conformal dielectric layer, until exposing the patterned first carbon-based film in the exclusion area, and while also preserving the structural integrity of the air gaps in the planarized non-conformal dielectric in the air gap area;

removing the patterned first carbon-based film in the exclusion area; and

blanket depositing and planarizing a filler dielectric so that the planarized filler dielectric occupies the region between the planarized metal interconnects in the exclusion area.

36. The method of claim 35, further comprising:

blanket depositing a second metal barrier liner before the deposition of the filler dielectric, wherein the removal of the patterned first carbon-based film in the exclusion area comprises a highly reactive hydrogen radicals process to remove the patterned carbon-based film and to pre-clean the surface of the planarized metal interconnects prior to the deposition of the second metal barrier liner, thus combining the removal and pre-clean processes into a single process.

37. A method of forming an interconnect structure comprising:

providing a substrate having a first level metal interconnect structure;

blanket depositing a second level ILD layer, a second level carbon-based film, a second level etch stop layer, and a second level hard mask layer;

blanket depositing and patterning a second level trench patterned photoresist layer;

transferring the second level trench pattern to the second level hard mask layer;

removing the second level trench patterned photoresist layer;

blanket depositing and patterning a second level via photoresist layer;

transferring the second level via pattern to the second level etch stop layer;

transferring the second level via pattern to the second level carbon-based film and removing the second level via patterned photoresist layer;

transferring the second level via pattern to the second level ILD layer;

transferring the second level via pattern to the surface the first level metal interconnect structure;

transferring the second level trench pattern to the second level via patterned etch stop to form a second level trench patterned etch stop;

transferring the second level trench pattern to the second level via patterned carbon-based layer to form a second level trench patterned carbon-based layer;

removing the second level trench patterned hard mask;

blanket depositing and planarizing a conductive metal to form a plurality of second level metal interconnect lines and a plurality of metal vias in contact with the first level metal interconnect structure;

removing the second level trench patterned etch stop layer to expose the second level trench patterned carbon-based film;

removing the second level trench patterned carbon-based film; and

blanket depositing and planarizing a second level non-conformal dielectric layer to forming a second level air gap in the planarized non-conformal dielectric layer in the regions between the second level metal interconnect lines.

38. The method of claim 37, wherein the transferring of the second level via pattern to the second level carbon-based film and the removing of the second level via patterned photoresist layer, are performed substantially simultaneously with substantially the same method of removing both photoresist material and carbon based film material.

39. The method of claim 37, further comprising blanket depositing a second level barrier metal liner, wherein the removal of the second level trench patterned carbon-based film comprises a highly reactive hydrogen radicals process to remove the patterned carbon-based film and to pre-clean the surface of the planarized metal interconnects prior to the deposition of the second metal barrier liner, thus combining the removal and pre-clean processes into a single process.

40. A method of forming an interconnect structure comprising:

providing a substrate having a first level metal interconnect structure and a first level barrier layer cap;

blanket depositing a second level ILD layer, a second level carbon-based film, a second level etch stop film, and a second level hard mask layer;

blanket depositing and patterning a second level via patterned photoresist layer;

transferring the second level via pattern to the second level hard mask layer and the second level etch stop film;

transferring the second level via pattern to the second level carbon-based film and removing the second level via patterned photoresist layer;

transferring the second level via pattern to the second level ILD layer;

blanket depositing and patterning a second level trench patterned photoreist layer;

transferring the second level trench pattern to the second level hard mask layer and the second level etch stop film;

transferring the second level trench pattern to the second level via patterned carbon-based film and removing the second level trench patterned photoresist layer;

transferring the via pattern from the second level via patterned ILD layer to the first level barrier layer cap;

blanket depositing and planarizing a plurality of second level metal interconnect lines with a plurality of metal vias in contact with the first level metal interconnect structure;

removing any remaining portion of the second level trench patterned hard mask layer and the second level trench patterned etch stop film;

removing the second level trench patterned carbon-based film; and

blanket depositing and planarizing a second level non-conformal dielectric layer, whereby forming second level air gaps in the dielectric regions between the second level metal interconnect lines.

41. The method of claim 40, wherein the transferring of the second level via pattern to the second level carbon-based film and the removing of the second level via patterned photoresist layer, are both performed substantially simultaneously with substantially the same method of removing both photoresist and carbon-based film material.

42. The method of claim 40, wherein the transferring of the second level trench pattern to the second level via patterned carbon-based film and the removing of the second level trench patterned photoresist layer, are both performed substantially simultaneously with substantially the same method of removing both photoresist and carbon-based film material.

43. The method of claim 40, further comprising blanket depositing a second level barrier metal liner, wherein the removal of the second level trench patterned carbon-based film comprises a highly reactive hydrogen radicals process to remove the patterned carbon-based film and to pre-clean the surface of the planarized metal interconnects prior to the deposition of the second metal barrier liner, thus combining the removal and pre-clean processes into a single process.

44. A method of forming an interconnect structure comprising:

providing a substrate having a first level metal interconnect structure and a second level ILD layer;

blanket depositing and patterning a second level via patterned photoresist layer;

transferring the second level via pattern to the second level ILD layer and to the surface of the first level metal interconnect structure;

removing the second level via patterned photoresist layer;

performing a blanket metallization deposition and planarization to form a plurality of metal vias in electrical contact with the first metal interconnect structure;

selectively depositing a selective via metal cap over the metal vias;

blanket depositing a second level carbon-based film and a second level hard mask layer;

blanket depositing and patterning a second level trench patterned photoresist layer;

transferring the second level trench pattern to the second level second hard mask layer;

transferring the trench pattern onto the second level carbon-based film to form a second level trench patterned carbon-based film;

removing the second level trench patterned photoresist layer;

removing the second level trench patterned hard mask layer;

blanket depositing and planarizing a metal layer to form a plurality of second level metal interconnect lines in electrical contact with the metal vias;

removing the second level trench patterned carbon-based film; and

blanket depositing and planarizing a second level non-conformal dielectric layer forming second level air gaps in the dielectric regions between the second level metal interconnect lines.

45. The method of claim 44, wherein the transferring of the trench pattern onto the second level carbon-based film, and the removing of the second level trench patterned photoresist layer, are both performed substantially simultaneously with substantially the same method of removing both photoresist and carbon-based film material.

46. The method of claim 44, further comprising blanket depositing a second level barrier metal liner, wherein the removal of the second level trench patterned carbon-based film comprises a highly reactive hydrogen radicals process to remove the patterned carbon-based film and to pre-clean the surface of the planarized metal interconnects prior to the deposition of the second metal barrier liner, thus combining the removal and pre-clean processes into a single process.