Method for ion implanting insulator material to reduce dielectric constant

• US 20050191828A1
• Filed: 12/01/2004
• Published: 09/01/2005
• Est. Priority Date: 08/11/2000
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Ramaswamy, Kartik, Hanawa, Hiroji, Collins, Kenneth S., Nguyen, Andrew, Al-Bayati, Amir, Roberts, Rick J., Gallo, Biagio, MacWilliams, Ken
• Granted Patent: US 7,166,524 B2
• Time in Patent Office: Days
• US Class Current: 438/514
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01L 21/76254 with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond

Abstract

An integrated microelectronic circuit has a multi-layer interconnect structure overlying the transistors consisting of stacked metal pattern layers and insulating layers separating adjacent ones of said metal pattern layers. Each of the insulating layers is a dielectric material with plural gas bubbles distributed within the volume of the dielectric material to reduce the dielectric constant of the material, the gas bubbles being formed by ion implantation of a gaseous species into the dielectric material.

Claims

1. A material having a reduced dielectric constant, comprising a dielectric layer containing gas bubbles formed by ion implantation of a gaseous species into said layer.

2. The material of claim 1 wherein said gas bubbles occupy between 5% and 50% by volume of said dielectric layer.

3. The material of claim 1 wherein said gaseous species is a gaseous species.

4. The material of claim 3 wherein said gaseous species comprises one or combination of hydrogen, helium, nitrogen, neon, argon, krypton, xenon, fluorine, chlorine, iodine, bromine, oxygen.

5. The material of claim 1 wherein said gas bubbles have an average diameter of between about 1 nm and 10 nm.

6. The material of claim 1 wherein said lattice is non-crystalline.

7. A material comprising an amorphous or polycrystalline or crystalline lattice of one or more atomic species, said lattice being a dielectric material, and plural bubbles distributed within the volume of said lattice and formed by ion implantation of a gaseous species into said lattice.

8. The material of claim 7 wherein said bubbles occupy a proportion between 1% and 50% by volume of said lattice.

9. The material of claim 8 wherein said dielectric material has a dielectric constant reduced in accordance with said proportion.

10. The material of claim 7 wherein each of said bubbles contains a vacuum, said gaseous species having evaporated from said bubbles after ion implantation.

11. The material of claim 10 wherein said gaseous species comprises one or combination of hydrogen, helium, nitrogen, neon, argon, krypton, xenon, fluorine, chlorine, iodine, bromine, oxygen.

12. The material of claim 7 wherein said bubbles have an average diameter of between about 1 nm and 5 nm.

13. The material of claim 7 wherein said lattice is non-crystalline.

14. An integrated circuit comprising a semiconductor substrate and plural films on said semiconductor substrate, at least one of said films being an insulation layer, and plural bubbles distributed within the volume of said lattice and formed by ion implantation of a gaseous species into said lattice.

15. An integrated microelectronic circuit comprising plural transistors and a multi-layer interconnect structure overlying said transistors and comprising stacked metal pattern layers and insulating layers separating adjacent ones of said metal pattern layers, each of said insulating layers comprising a dielectric material, and plural bubbles distributed within the volume of said dielectric material and formed by ion implantation of a gaseous species into said dielectric material.

16. A method of forming a low dielectric constant insulating film on a workpiece, comprising:

forming a dielectric layer on said workpiece; and

ion implanting a gaseous species into said dielectric layer so as to form gas bubbles in said dielectric layer.

17. The method of claim 16 further comprising regulating the average diameter of said gas bubbles by regulating the energy of the ions of said gaseous species during the step of ion implanting.

18. The method of claim 16 further comprising regulating the average diameter of said gas bubbles by regulating the temperature of said workpiece during the ion implanting step.

19. The method of claim 16 further comprising regulating the average diameter of said bubbles by regulating the ion implantation dose of the ion implantation step.

20. The method of claim 16 further comprising regulating the average diameter of said gaseous species by ion implanting a bubble-enhancing species.

21. The method of claim 20 wherein said bubble-enhancing species comprises one of boron, phosphorus, arsenic, carbon, germanium.

22. The method of claim 21 wherein said gaseous species comprises one or combination of hydrogen, helium, nitrogen, argon, xenon, neon, krypton, fluorine, chlorine, iodine, bromine, oxygen.

23. The method of claim 16 further comprising causing the gas in said bubbles to evolve from said bubbles so that each bubble contains a vacuum.

24. The method of claim 23 wherein the step of causing the gas to evolve from the bubbles comprises performing a post-implantation anneal step.

25. The method of claim 16 wherein the step of ion implanting comprises:

placing said workpiece in a vacuum chamber having at least one external reentrant conduit;

introducing a process gas comprising a precursor of the gaseous species to be ion implanted; and

coupling RF power to process gases in said reentrant conduit to generate an oscillating plasma current in a torroidal path that includes said reentrant conduit and a process zone adjacent the surface of the workpiece.

26. The method of claim 25 further comprising applying RF plasma bias power to said workpiece.

27. The method of claim 25 wherein said process gas further comprises a bubble-enhancing species.

28. The method of claim 25 wherein said precursor comprises a molecular form of said gaseous species.

29. The method of claim 25 wherein said process gas further comprises a bubble-enhancing species.

30. The method of claim 29 wherein said bubble-enhancing species tends to limit the average size of said gas bubbles.

31. The method of claim 29 wherein said bubble-enhancing species tends to improve the stability of said gas bubbles.

32. The method of claim 29 wherein said bubble-enhancing species comprises one of boron, phosphorus, arsenic, carbon, germanium.

33. The method of claim 16 wherein the step of forming a dielectric layer and the step of ion implanting are carried out contemporaneously.

34. The method of claim 25 wherein the step of forming a dielectric layer and the step of ion implanting are carried out contemporaneously, and wherein said process gas further comprises a precursor of the dielectric material of said dielectric layer.

35. The method of claim 34 wherein said precursor of said dielectric material is a gas mixture comprising silane and oxygen or SiF4 and oxygen.

36. The method of claim 34 wherein said precursor of said dielectric material is a gas mixture comprising silane and nitrogen, or silane and oxygen.

37. The method of claim 34 further comprising applying an RF bias voltage to said workpiece corresponding to an implant depth profile relative to a top surface of said dielectric layer that is less than the final thickness of said dielectric layer.

38. The method of claim 37 wherein the top surface of said dielectric layer rises during the contemporaneous deposition and implantation steps, whereby said implant depth profile rises contemporaneously.

39. The method of claim 18 wherein:

said ion energy corresponds to a shallow ion implantation depth profile relative to a desired final thickness of said dielectric layer;

the step of depositing a dielectric layer deposits a thin dielectric layer corresponding to said shallow ion implantation depth profile whereby to implant substantially the entire thin dielectric layer; and

the steps of depositing and implanting are repeated in alternating sequence to form a stack of thin dielectric layers each ion implanted with the gaseous species to form gas bubbles therein.

53. The method of claim 16 wherein the step of ion implanting is a carried out by plasma immersion ion implantation.

54. The method of claim 53 wherein the step of plasma immersion ion implantation is carried out in a chamber having an external reentrant conduit completing a toroidal path extending through a plasma process zone of the chamber and generating an oscillating RF plasma current in the toroidal path.

40. A method of forming a thin film on a semiconductor structure with enhanced adhesion, comprising:

depositing an overlying dielectric film on an underlying layer of a semiconductor structure; and

performing plasma immersion ion implantation on said semiconductor structure to form a boundary layer at the interface between the dielectric film and the underlying layer containing atoms from both said dielectric layer and said underlying layer.

41. A method of forming a porous dielectric film of a semiconductor structure with enhanced hardness of the porous dielectric film, comprising:

depositing an overlying porous dielectric film on an underlying layer of a semiconductor structure; and

performing plasma immersion ion implantation of a gaseous species on said semiconductor structure to fill pores of said porous film with gas.

42. A method of forming a porous dielectric film on a semiconductor structure having reduced tensile stress, comprising:

depositing an overlying porous dielectric film on an underlying layer of a semiconductor structure; and

performing plasma immersion ion implantation on said semiconductor structure to break atomic bonds within said porous film.

43. A method of forming a porous dielectric film on an underlying layer of a semiconductor structure having enhanced adhesion with the underlying layer, reduced tensile stress and enhanced hardness, comprising:

depositing an overlying porous dielectric film on an underlying layer of a semiconductor structure; and

performing plasma immersion ion implantation on said semiconductor structure of a gaseous species to break atomic bonds within said porous film, to form a boundary layer at the interface between the dielectric film and the underlying layer containing atoms from both said dielectric layer and said underlying layer, and to fill pores of said porous film with gas.

44. A method of forming a dielectric film on an underlying layer of a semiconductor structure having reduced dielectric constant, reduced tensile stress and enhanced hardness, comprising:

depositing an overlying dielectric film on an underlying layer of a semiconductor structure, and doping the dielectric film with a first species that reduces the dielectric constant of the dielectric film; and

increasing the hardness of said dielectric film by ion implanting a second species into said dielectric film.

45. The method of claim 44 wherein the step of doping said dielectric film creates pores in said dielectric film and wherein the step of ion implanting said second species breaks said pores into smaller pores with said second species.

46. The method of claim 44 wherein said first species comprises one of (a) a semiconductor species, (b) a non-conductor species.

47. The method of claim 46 wherein said second species comprises a gaseous species.

48. The method of claim 46 wherein said second species comprises a non-gaseous species that is one of (a) a semiconductor species, (b) a non-conductor species.

49. A method of forming a dielectric film on an underlying layer of a semiconductor structure having reduced dielectric constant, reduced tensile stress and enhanced hardness, comprising:

depositing an overlying dielectric film on an underlying layer of a semiconductor structure; and

decreasing the dielectric constant of said dielectric film by ion implanting a first species into said dielectric film so as to dope said dielectric film with said first species, while simultaneously enhancing the hardness of the doped dielectric film by ion implanting a second species into said dielectric film.

50. The method of claim 49 wherein said first species comprises one of (a) a semiconductor species, (b) a non-conductor species.

51. The method of claim 50 wherein said second species comprises a gaseous species.

52. The method of claim 50 wherein said second species comprises a non-gaseous species that is one of (a) a semiconductor species, (b) a non-conductor species.