Plasma immersion ion implantation process using an inductively coupled plasma source having low dissociation and low minimum plasma voltage

• US 7,303,982 B2
• Filed: 08/22/2003
• Issued: 12/04/2007
• Est. Priority Date: 08/11/2000
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Ramaswamy, Kartik, Hanawa, Hiroji, Collins, Kenneth S., Nguyen, Andrew, Al-Bayati, Amir, Gallo, Biagio, Monroy, Gonzalo Antonio
• Primary Examiner(s): GHYKA, ALEXANDER G
• Application Number:
  US10/646,467
• Publication Number:
  US 20050051272A1
• Time in Patent Office: 1,565 Days
• Field of Search: 438/513, 438/514, 438/530, 156/345.48, 156/345.49
• 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

Abstract

A method for implanting ions in a surface layer of a workpiece includes placing the workpiece on a workpiece support in a chamber with the surface layer being in facing relationship with a ceiling of the chamber, thereby defining a processing zone between the workpiece and the ceiling, and introducing into the chamber a process gas which includes the species to be implanted in the surface layer of the workpiece. The method further includes generating from the process gas a plasma by inductively coupling RF source power into the processing zone from an RF source power generator through an inductively coupled RF power applicator, and applying an RF bias from an RF bias generator to the workpiece support.

Claims

1. A method for ion implanting a species at a desired implant depth in a workpiece, comprising:

placing said workpiece on a workpiece support in a chamber with said workpiece being in facing relationship with a ceiling of said chamber, thereby defining a processing zone between said workpiece and said ceiling;

introducing into said chamber a process gas comprising the species to be implanted in said workpiece;

generating from said process gas a plasma by inductively coupling RF source power into said processing zone from an RF source power generator through an inductively coupled RF power applicator;

applying an RF bias from an RF bias generator to said workpiece support; and

controlling ion implantation depth of said species in said workpiece by setting said RF bias to a level corresponding to said desired implant depth.

2. The method of claim 1 wherein said RF

bias has a bias frequency that is sufficiently low for ions in a plasma sheath near said workpiece to attain an ion energy at least nearly equivalent to a peak-to-peak voltage of said RF bias generator.

3. The method of claim 2 wherein said bias frequency is sufficiently high so that RF voltage drops across dielectric layers on said workpiece do not exceed a predetermined fraction of an RF bias voltage applied to said workpiece support by said RF bias generator.

4. The method of claim 3 wherein said predetermined fraction corresponds to about 10%.

5. The method of claim 1 wherein said workpiece comprises a semiconductor material, and said species to be implanted comprises a dopant impurity that promotes one of a p-type or n-type conductivity in said semiconductor material, and wherein said desired depth to which said element is to be implanted corresponds to a desired p-n junction depth.

6. The method of claim 5 wherein said gas comprises a chemical combination of said dopant impurity and another element.

7. The method of claim 6 wherein said gas comprises a fluoride of said dopant impurity.

8. The method of claim 6 wherein said gas comprises a hydride of said dopant impurity.

9. The method of claim 6 wherein said gas further comprises a co-implant ion bombardment element which removes from a top surface of said workpiece a material that tends to accumulate during implantation of said dopant impurity.

10. The method of claim 1 wherein said workpiece comprises a semiconductor crystal which is to be implanted with a dopant impurity element, and wherein said species comprises a pre-implant ion bombardment species that creates damage in said semiconductor crystal.

11. The method of claim 1 wherein said workpiece comprises a dielectric thin film, and wherein said species comprises a surface-enhancement species which enhances a characteristic of said dielectric thin film upon implantation and substitution.

12. The method of claim 11 wherein said characteristic is the electrical behavior of said dielectric thin film.

13. The method of claim 11 wherein said dielectric thin film comprises an oxide of a semiconductor element, and said species comprises a non-oxygen element to be substituted for oxygen atoms in said dielectric thin film.

14. The method of claim 1 wherein the step of placing said workpiece on said workpiece support is preceded by:

introducing a passivation process gas containing passivation-forming chemical species;

forming a passivation layer on interior surfaces of said chamber by generating from said passivation gas a plasma in said processing zone.

15. The method of claim 14 wherein said passivation gas comprises one of a hydride, a fluoride or an oxide of a semiconductor element.

16. The method of claim 15 wherein said passivation gas comprises a chemical species containing carbon and fluorine.

17. The method of claim 14 wherein the step of generating a plasma from said process gas is followed by:

removing said process gas from said chamber;

removing said workpiece from said chamber;

introducing a passivation layer-removing gas into said chamber;

generating from said passivation layer-removing gas, a plasma in said processing zone, so as to remove said passivation layer from said interior surfaces of said chamber.

18. The method of claim 17 further comprising heating said interior surfaces of said chamber during the removal of said passivation layer.

19. The method of claim 17 wherein said passivation layer-removing gas comprises a fluorine-containing gas.

20. The method of claim 17 wherein said passivation layer-removing gas comprises a hydrogen-containing gas.

21. The method of claim 1 wherein the step of introducing said process gas is preceded by:

pre-cleaning said wafer.

22. The method of claim 21 wherein the step of pre-cleaning said wafer comprises removing an accumulated layer therefrom.

23. The method of claim 22 wherein the step of removing comprises removing an oxide layer from said workpiece.

24. The method of claim 23 wherein the step of removing an oxide layer comprises etching said oxide layer.

25. The method of claim 1 wherein the step of generating a plasma from said process gas is followed by:

heating a layer of said workpiece to an anneal temperature sufficiently high to cause atoms of the species implanted in said layer to be substituted into atomic sites in a crystal lattice of said layer.

26. The method of claim 25 wherein said layer is masked by a photolithographic layer defining a pattern of ion implantation, and wherein the step of heating said surface is preceded by:

removing said photolithographic layer.

27. The method of claim 26 wherein the step of removing said photolithographic layer is carried out in a pyrolization chamber.

28. The method of claim 25 wherein the step of heating said layer is carried out after removing said workpiece from said chamber and placing it in an anneal chamber.

29. The method of claim 9 wherein said process gas is one of (a) hydride of said dopant species or (b) a fluoride of said dopant species, and said ion bombardment element comprises one of:

Helium, Hydrogen, a semiconductor element of the type including Silicon, Germanium, Carbon, a fluoride of a semiconductor element of the type including fluorides of Silicon, Germanium, Carbon.

30. The method of claim 17 wherein said passivation layer-removing gas comprises NF3.

31. The method of claim 5 wherein said semiconductor material is silicon and said dopant impurity is boron.

32. The method of claim 5 wherein said semiconductor element is silicon and said dopant impurity is phosphorus.

33. The method of claim 5 wherein said semiconductor element is silicon and said dopant impurity is arsenic.

34. The method of claim 5 wherein said semiconductor element comprises one of silicon or germanium.

35. The method of claim 1 wherein:

said workpiece comprises plural dielectric gates formed over an underlying layer having horizontal and non-horizontal surfaces;

the step of applying bias power comprises selecting a level of said bias power promotive of a sufficiently collisional plasma sheath over said workpiece to produce a significant fraction of ions impacting said layer at trajectories other than orthogonal to said layer whereby to implant ions in said horizontal and non-horizontal surfaces of said layer.

36. The method of claim 5 wherein said workpiece comprises a crystal lattice and wherein the step of generating a plasma from said process gas is preceded by:

introducing into said chamber an amorphizing gas comprising an ion bombardment species;

generating from said amorphizing gas a plasma in said processing zone;

applying bias power to said workpiece support to attract ions of said ion bombardment species from said plasma toward said workpiece whereby said ions cause damage in said crystal lattice to amorphize said crystal lattice.

37. The method of claim 36 wherein said ion bombardment species comprises a semiconductive species.

38. The method of claim 37 wherein said ion bombardment species comprises one of silicon or germanium.

39. The method of claim 6 wherein said process gas further comprises an ion bombardment species for co-implantation with said dopant impurity in said workpiece.

40. The method of claim 39 wherein ions of said ion bombardment species are implanted in said workpiece to cause crystal lattice damage for amorphizing said at least a surface portion of said workpiece during implantation of said dopant impurity in said workpiece.

41. The method of claim 40 wherein said ion bombardment species comprises a semiconductor species.

42. The method of claim 41 wherein said semiconductor species comprises one of silicon or germanium.

43. The method of claim 1 wherein said bias comprises RF power.

44. The method of claim 43 further comprising pulse modulating said RF bias power.

45. The method of claim 44 further comprising pulse modulating said RF source power.

46. The method of claim 45 further comprising maintaining a relation between the pulse modulating of said RF bias power and the pulse modulating of said RF source power that is one of:

(a) push-pull;

(b) in-synchronism;

(c) symmetrical;

(d) non-symmetrical.

47. The method of claim 1 wherein the step of applying said bias power comprises applying a single burst of said bias power to said workpiece support.

48. The method of claim 47 wherein said single burst has a duration corresponding to a desired implant dosage.

49. The method of claim 48 further comprising:

sensing when a voltage measured near said workpiece support reaches a threshold corresponding to the desired implant depth in response to applying said bias power;

triggering a clock in response to said sensing step, and terminating said bias power when said clock reaches said duration.

50. The method of claim 43 further comprising controlling said bias power so as to produce a bias voltage near said workpiece support at least nearly equal to said threshold.

51. The method of claim 1 wherein said RF bias generator has a bias frequency that is sufficiently low for ions in a plasma sheath near said workpiece to follow electric field oscillations across said sheath at said bias frequency.

52. The method of claim 51 wherein said bias frequency is sufficiently high so that RF voltage drops across dielectric layers on said workpiece do not exceed a predetermined fraction of the RF bias voltage applied to said workpiece support.

53. The method of claim 52 wherein said predetermined fraction corresponds to about 10%.

54. The method of claim 1 wherein said RF bias generator has a bias frequency between 10 kHz and 10 MHz.

55. The method of claim 1 wherein said RF bias generator has a bias frequency between 50 kHz and 5 MHz.

56. The method of claim 1 wherein said RF bias generator has a bias frequency between 100 kHz and 3 MHz.

57. The method of claim 1 wherein said RF bias generator has a bias frequency of about 2 MHz to within about 5%.

58. The method of claim 1 wherein said species to be implanted comprises a first atomic element, said process gas further comprising:

a second atomic element in chemical combination with said first atomic element.

59. The method of claim 58 wherein said workpiece is a semiconductor material and said first atomic element is an n-type or p-type conductivity dopant impurity with respect to said semiconductor material.

60. The method of claim 59 wherein said second atomic element comprises a semiconductor element.

61. The method of claim 60 wherein said second atomic element and said semiconductor material of said workpiece are the same atomic element.

62. The method of claim 59 wherein said second atomic element is an element having a greater tendency than said first atomic element following ion implantation to diffuse out of said workpiece upon heating of said workpiece.

63. The method of claim 59 wherein said second atomic element comprises one of hydrogen and fluorine.

64. The method of claim 59 wherein the chemical combination of said first and second atomic species comprises a first molecular species, said process gas further comprising a second molecular species.

65. The method of claim 64 wherein said second molecular species comprises one of:

(a) hydrogen gas, (b) fluorine-containing gas.

66. The method of claim 63 wherein said first molecular species comprises a fluoride of said dopant impurity and said second molecular species comprises a hydride of said dopant impurity.

67. The method of claim 66 wherein said process gas further comprises a third molecular species.

68. The method of claim 67 wherein said third molecular species comprise at least one of (a) hydrogen-containing gas, fluorine-containing gas, (c) an inert gas.

69. The method of claim 1 further comprising:

providing a cleaning plasma species source reactor;

prior to the step of introducing said workpiece, producing a plasma in said cleaning species source reactor from chamber cleaning species precursor gases to produce chamber cleaning plasma species;

furnishing said chamber cleaning plasma species from said cleaning species source reactor into said plasma immersion ion implantation reactor so as to clean interior surfaces of said plasma reactor, and then removing said chamber-cleaning plasma species from said plasma immersion ion implantation reactor.

70. The method of claim 69 wherein said chamber cleaning precursor gases comprise a fluorine-containing species and said chamber cleaning plasma species comprise fluorine-containing radicals.

71. The method of claim 69 wherein said chamber cleaning precursor gases comprise a hydrogen-containing species and said chamber cleaning plasma species comprise hydrogen-containing radicals.

72. The method of claim 1 further comprising:

providing an optical metrology chamber;

obtaining a measurement of ion implantation in a workpiece previously processed in said plasma immersion ion implantation reactor;

adjusting said magnitude of said bias in accordance with said measurement.

73. The method of claim 1 further comprising:

providing an ion beam implantation apparatus;

placing said workpiece in said ion beam implantation apparatus and implanting a second species in said workpiece.

74. The method of claim 73 wherein said workpiece comprises a semiconductor material, and said first and second species are dopant impurities of opposite conductivity types relative to said semiconductor material.

75. The method of claim 74 further comprising:

masking devices on said workpiece of one conductivity type and exposing devices of an opposite conductivity type during ion implantation of said first species in said plasma immersion ion implantation reactor;

masking devices on said workpiece of said opposite conductivity type and exposing devices of the one conductivity type during ion implantation of said second species in said ion beam implantation apparatus.

76. The method of claim 75 wherein said first species is of a lower mass than said second species.

77. The method of claim 75 wherein said first species comprises boron and said second species comprises arsenic.

78. The method of claim 1 further comprising:

providing an anneal chamber;

after the step of generating a plasma, removing said workpiece from said plasma immersion ion implantation reactor and placing it in said anneal chamber, and heating at least a surface portion of said workpiece sufficiently to cause at least some of the species ion implanted in said workpiece to be substituted into crystal lattice atomic sites of said workpiece.

79. The method of claim 78 wherein the step of heating comprises a dynamic surface anneal process.

80. The method of claim 1 further comprising:

providing a photoresist strip chamber;

the step generating a plasma is followed by placing said workpiece in said photoresist strip chamber and removing photoresist from said workpiece.

81. The method of claim 1 further comprising:

providing a wet clean chamber;

and wherein the step of generating said plasma is followed by placing said workpiece in said wet clean chamber.

82. The method of claim 1 further comprising:

providing a second plasma immersion ion implantation reactor;

placing said workpiece in said second plasma immersion ion implantation reactor and implanting a second species in said workpiece.

83. The method of claim 82 wherein said workpiece comprises a semiconductor material, and said first and second species are dopant impurities of opposite conductivity types relative to said semiconductor material.

84. The method of claim 83 further comprising:

masking devices on said workpiece of one conductivity type and exposing devices of an opposite conductivity type during ion implantation of said first species in said plasma immersion ion implantation reactor;

masking devices on said workpiece of said opposite conductivity type and exposing devices of the one conductivity type during ion implantation of said second species in said second plasma immersion ion implantation reactor.