1. Jari Koskinen, Sami Franssila jari.koskinen@aalto.fi 1.9.2016
XXX Thin Film Technology Doctoral course Plasma and ion bombardment (8 credits)
Jari Koskinen, Sami Franssila

2. Contents plasma systems 2nd hour ion beam surface interactions Plasma
basic physics, parameters, ionization
types of plasma
generation of plasma
emission of ions,
plasma systems
2nd hour ion beam surface interactions
collisions, cascades
range
sputtering
simulations
mixing

3. Plasma
Plasma
Gas of positive ions, electrons and (mostly) neutral atoms
Etymology: Greek: “moulded” - plasma fills the chamber
Charge neutrality ne = ni
Colliding electrons ionise atoms
Ions and electrons accelerate in electric field
Collisions excite atoms
De-excitation creates photons – visible light

4. Important plasma parameters
Oscillations
Debye length
mean free path
ionization crossection

5. Hannu Koskinen Univ of Helsinki

6. hot&dense
<< 1
cold&sparce
Hannu Koskinen Univ of Helsinki

8. Different types of plasmas
Thin film plasma processes
Wikipedia

9. n = density of atoms (and ions) Total collistion cross section:
Hannu Koskinen Univ of Helsinki
n = density of atoms (and ions)
Total collistion cross section:
σtotal = σexitation + σion + σattachment+ σother
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

10. Electron temperature
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

11. Electron and ion temperature
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

12. Plasma sheath e.g. for practical sputter plasma ds ≈ some tens x λD
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

13. Cold cathode discharge
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

14. Types of disharge Typical mode in sputter deposition
Mahan, Physical Vapor Deposition of Thin Films, Wiley

15. Luminous regions in DC plasma
ions neutralize
secondary electrons have slowed for max ionization
electrons have accelerated sufficiently for ionization
Mahan, Physical Vapor Deposition of Thin Films, Wiley

16. Practical sputtering plasma -1
Argon pressure 1 torr
atom density (n) 3 x 1016 cm-3
ni=ne cm-3
ionization fraction 3 x 10-7 (weakly ionized plasma)
ion temperature Ti 300K
electron temperature Te 23,000K

17. Densities and temperatures in process plasmas
seconday electrons thru cathode sheath
ions and neutrals back scattered form cathode
ions accelerated to cathode
electrons in main plasma
dissociation products: ions&neutrals
ions in main plasma
process gas atoms&neutrals

18. Practical sputtering plasma -2
VDC 1000V
Vp 8V
Current density at cathode 2 mA/cm2
Cathode sheath L 2 mm
mean free path λ 50 µm
Mahan, Physical Vapor Deposition of Thin Films, Wiley

19. Circuit models of DC plasma discharge
Mahan, Physical Vapor Deposition of Thin Films, Wiley

20. Ion energy at cathode Ar+(hot) + Ar(cold)  Ar(hot)+Ar+(cold)
σ = 2.5 x cm-3
Mahan, Physical Vapor Deposition of Thin Films, Wiley

21. AC plasma methods

22. AC plasma
Bunshah, Handbook of Deposition Technologies for Films and Coatings Noyes

23. Forming of self-bias in AC discharge
Mahan, Physical Vapor Deposition of Thin Films, Wiley

24. Self bias at electrodesn
n= 4 (sometimes 2)
No simple model.
One argument: “ impedance of smaller
are electrode is higher
-> higher potential difference”
Sivu 24

25. Circuit models of RF plasma discharge
Mahan, Physical Vapor Deposition of Thin Films, Wiley

26. RF Plasma glow discharge

27. Arc plasma

28. Arc discharge deposition
Arc discharge video

29. Arc disharge – cathode spot

30. Arc discharge process arc current concentrated into filaments – arcs
intense electron emission
intense ion emission due to electron current ( atoms/electrons – 1/100)
ionization of atoms – formation of plasma
flow of ions to cathode – intense sputtering of atoms
A/m2
overlapping thermal spikes
materials is melted and sublimated in cathode spots
cathode spots move randomly or could be steered by using magnets
electons ionize vapor and create more electrons – increase of current
ions accelerate
due to potential difference in plasma
due to multiple collisions with fast electrons
macro particles (up to 10 µm diam.I are formed
Timko, Nordlund simulations

31. Filtered arc

32. HIPIMS

33. HIPIMS
W. Sproul, AEPSE 2009 Tutorial
“Pulsed Plasma Diffusion”

34. HIPIMS
W. Sproul, AEPSE 2009 Tutorial

35. HIPIMS
W. Sproul, AEPSE 2009 Tutorial

36. HIPIMS Cr
W. Sproul, AEPSE 2009 Tutorial

37. HIPIMS
W. Sproul, AEPSE 2009 Tutorial

38. Fluxes of ions in HIPIMS
J. Vac. Sci. Technol. A, Vol. 28, No. 4, Jul/Aug 2010
Sivu 38

39. HIPIMS denser films
W. Sproul, AEPSE 2009 Tutorial

40. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

41. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

42. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

43. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

44. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

45. Reactive sputtering
W. Sproul, AEPSE 2009 Tutorial

46. Ion solid interarctions

47. Energetic ion surface interactions

48. Secondary electrons

49. Desorption, cleaning

50. Sputtering

51. Collision cascade, thermal spike
K. Nordlund

52. doping, compounds

53. Range of ions
Sivu 53

54. Range
Sivu 54

55. Collision cascades
Sivu 55

56. Range and stopping
range:
enegy loss:
stopping:
Sivu 56

57. Reduced stopping
Sivu 57

58. 10 keV Si recoil atom in silicon
K. Nordlund

59. 1 keV C+ in glass, Range

60. Range and damage 30 keV Ne+ in ZrO2

61. Kai Nordlund Univ of Helsinki Simulations

62. Sputtering Source of atoms and ions
Cleaning: Removing lose atoms, impurities, oxides
Sivu 62

63. Sputter constant
low ion energies < 1 keV
Sivu 63

64. Sputtering yield

65. Sputter yield angle dependence

66. Sputter yield angle dependence and energy distribution

67. Sputter yield angle dependence and energy distribution

68. Energy distribution of sputteres atoms
Usb/2
1/E2
Sivu 68

69. Preferential sputtering
Sivu 69

70. TRIM and SRIM simulations
Sivu 70