Mgr. Jan Čech, Ph.D., Masarykova univerzita 19.9.2014, Brno, Vysoké učení technické v Brně...

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Mgr. Jan Čech, Ph.D., Masarykova univerzita

19.9.2014, Brno, Vysoké učení technické v Brně

VÝBOJE V PLYNECH A JEJICH VYUŽITÍ-

I. NÍZKOTLAKÉ TECHNOLOGIE

Mgr. Jan Čech, Ph.D., Masaryk University

19.9.2014, Brno, Brno University of Technology

GAS DISCHARGES AND THEIR APPLICATIONS

-I LOW PRESSURE TECHNOLOGIES

Ref. Fig1a,b Ref. Fig2

Ref. Fig3

Ref. Fig4

LOW PRESSURE PLASMA AROUND US

• We are critically dependent on the technologies based on the low-pressure plasma utilization

• Automotive industry – engine (DLC layers), Headlights (reflectors, polymer covers protection), AR / anti-IR layers

• Machinery parts – surfaces of cutting tools

• Microelectronics – all processes of IC manufacturing, LCD, AR coatings of lenses, …

• Lighting – fluorescent tubes, neon tubes, …

WHAT TYPE OF APPLICATIONS IS (LOW PRESSURE) PLASMA WORTHY?• “Star wars” weapons

Ref. Fig5

• Medicinal therapy – Postřižiny movie

Ref. Fig6

• Space ships propulsion

Ref. Fig7

• Source of ions and active particles

Ref. Fig8

• Source of ions and active particles

• Source of radiation (light)

Ref. Fig9

LECTURE OUTLINE

• PART I: LOW PRESSURE

• PART II: LOW PRESSURE PLASMA TECHNOLOGIES

HISTORY OF LOW PRESSURE

• Vacuum – from lat. as „vacant/empty“

• From that is the Czech word „vzduchoprázdno“

• 1643 – first vacuum (E. Torricelli)

• 1654 – Public demonstration – Magdeburg spheres (O. von Guericke)

• 1855 – gas discharges, mercury pump (Geissler)

• 1892 – Fleuss’s piston pump

Ref. Fig11Ref. Fig12

Ref. Fig12

HISTORY OF LOW PRESSURE

1745 – von Kleist: Leyden bottle1752 – Franklin: lightning, as electricity phenomenon1860 – Maxwell: free mean path1876 – Goldstein: Cathode rays (e-beam)1880 – de la Rue: Paschen law1905 – Einstein: charged particles diffusion1925 – Langmuir: sheath theory1928 – Langmuir: “plasma”1929 – Debye: shielding – Debye length

Ref. Fig14

GAS UNDER MICROSCOPE

• Gas is composed of large number of moving particles. That collide with each other and also with the walls of the gas container (wall impacts) in which the gas is enclosed – i.e. producing the “gas pressure”

• How many particles contains 1 cm3 under standard conditions?

• NL = 2,9 x 1019 (= NA/Vm)

GAS UNDER MICROSCOPE

• Just a big billiard

• For given gas temperature and particle concentration the so-called “mean free path” between collisions could be defined

• How many particles are impacting the unity surface area?

• Nu = ¼ n.va – collision frequency

• For bounce back they have to interact with the wall. That implies force effect, under momentum conservation law =

• Gas pressure …

WILD BILLIARD AROUND US

• Mean free path (between two consecutive collisions)

• Depends on:

• Number of targets (gas density – n) and projectile diameter – d

• Projectiles velocities (gas temperature – T)

• Ideal gas law: p = nkT, where p is gas pressure, k is gas constant

• I.e. p , ↘ then n ↘ and thus d ↗

• Ek = F.d = q.E.d = q.U.d/D

OK, WHAT THE “LOW PRESSURE” IS?

• Upper pressure boundary:

• The chemistry of plasma changes with the pressure increase – so-called triple collisions influence (typ. ~103..4 Pa) – e.g. volume vs. surface charges recombination

• At values of p.d > 200 Torr.cm the gas breakdown mechanism changes (Townsend mech. to streamer one – cathode composition does not play roles so far) … p.d > 26 kPa.cm

OK, WHAT THE “LOW PRESSURE” IS?

• Lower pressure boundary:

• When the gas pressure is too low, the accelerated electron crosses discharge volume without collision, thus it cannot ionize the gas and so it cannot ignite the gas breakdown/discharge (typ. ~10-1..10-2 Pa)

HOW THE LOW PRESSURE ACTS:

Ref. Fig15

PART II – PLASMA AND ITS APPLICATIONS

SO WHY THE LOW PRESSURE PLASMA?

• Why are we using plasma generated under low pressure?

• It is easy to ignite plasma (gas discharge) even in big volumes and high homogeneity.

• It is easy to influence the energy and flow of particles impacting on the substrate surface

• Easy of non-equilibrium plasma generation – i.e. plasma with neutral gas T << energy of charged particles

• High purity of processing, high level of process control

• Magnetic field utilization ωC > ωSR

Ref. Fig28

Ref. Fig29

PLASMA BEHAVIOR UNDER LOW PRESSURE

• Ambipolar diffusion – effect of electrical charged particles interaction / fast electrons are decelerated by slow and heavy ions, which are contrarily dragged by the electrons.

• Plasma is in non-equilibrium state under low pressure

• Charging of surfaces – creation of electric double layer

Ref. Fig30

Ref. Fig31

Ref. Fig32

BEHAVIOR OF CHARGED PARTICLES IN THE VICINITY OF THE WALLS/SURFACE

• Electrical double layer formation

• Stern-layer, Debye-Hückel theory

• Zeta-potential – common aspect of plasma and electrolytes

BEHAVIOR OF CHARGED PARTICLES IN ELECTROLYTE/ PLASMA

Ref. Fig34 Ref. Fig35

ELECTRICAL DOUBLE LAYER - SHEATH

Ref. Fig37

Ref. Fig38abc

• Differences:

• in electrolytes the charge transport is made of positive and negative ions of “equal” masses

• In plasma the dominant charge transfer (electric current) is realized by the fast negative particles = electrons

• Energetic electrons shift the dynamics of plasma-electrolyte to the various other interaction types

Ref. Fig39abc

Ref. 8

• Electrical double layer (EDL) gives a dynamics to the interactions of positive ions with the walls (by accelerating of them during crossing the EDL potential difference)

• Fast electrons charging of surfaces in plasma negatively – so-called floating potential

• Ions flow could be driven by the voltage offset of the wall/substrate – so-called “bias”, controlling the kinetics of particles to the surface

SELECTED GAS DISCHARGES UNDER LOW PRESSURE

• Glow discharge

Ref. Fig40

Ref. Fig41ab

• CCP – capacitive coupled plasma

• Energy transferred via electron-electric field interaction – acceleration via electric field

• Ions usually stationary – cannot follow fast changes of el. Field

• Using blocking capacitor the electrode “bias” is easily achievable – controlling the flow/energy of ions to toe substrate

SELECTED GAS DISCHARGES UNDER LOW PRESSURE - CCP

• ICP – inductive coupled plasma

• Energy transferred via magnetic field – using electric currents induced by the electromagnetic induction of high frequency magnetic field

• Advantage – electrodes are outside the plasma (low contamination of plasma) = often usage of ICP in analytical methods

SELECTED GAS DISCHARGES UNDER LOW PRESSURE (0,013..13 Pa)

• Typ. CCP RF discharge parameters:

• Ionization degree: 0,01%

• Charged particles density 1010-1011 cm-3 (quasi-neutrality)

• Electron temp.: 1-3 eV (electropositive gasses .. Ar, He, N2) 5-10 eV (electronegative gasses – Cl, F, CCl, SF6, O2) (1 eV approx. 12 000 K)

• Ion temp.: 0,05 eV (500 K) .. Ions are heavy, RF el. field does not influence them much

• Neutrals: 0,04 eV (300 K)

Ref. 9

Ref. Fig42 Ref. Fig43

Ref. Fig44

TYPES OF LOW-PRESS. PLASMAS

• Discharge: direct current, high. freq., microwave

• CCP / ICP

• Magnetized / Non-magnetized

• I.e. the way how the energy is transferred to the plasma

(outer el./mag. fields interaction with the plasma)

• Possibilities to influence the plasma parameters and charged

particles flow to the substrates (“bias”).

Ref. Fig45

SELECTED DISCHARGES AT LOW PRESSURE

Plasma source

Tel (K) log nel (m-

3)Pressure(Torr)

Power (W)

DC glow 2-5 16 0,1-5 100-300

RF glow 3-8 17 0,05-1 200-500

ECR 5-15 18 10-4-0,01 300-1000

ICP 5-15 18 10-3-0,01 500-2000

Helicon 5-15 18-19 0,01-0,1 500-2000

Ref. 3

APPLICATION OF PLASMA GENERATORS (REACTORS)

• Deposition – w/o plasma:

• From solid phase– evaporation deposition (thermal), sputtering (electron gun)

• From liquid phase – electroplating, electroless plating

• From gas phase – CVD (chemical vapor deposition), ALD (atomic layer deposition)

APPLICATION OF PLASMA GENERATORS (REACTORS)

• Deposition – with plasma (discharges):

• From solid phase – dc / magnetron sputtering (non-reactive / reactive)

• From gas phase – PECVD (plasma enhanced CVD)

• dc discharges, rf discharges (CCP, ICP), microwave ECR discharges, …

• uniformity, homogeneity, deposition rate, deposited surface area

• Possible also at high pressure…

APPLICATION OF PLASMA GENERATORS (REACTORS)• Removal of material from the surface

• Etching / materials: Si, metals (Al, Cu, alloys), dielectrics (SiO2, SixNy, MeOx, low-k dielectrics)

• High rates, uniformity, anisotropy, selectivity

• Ashing– ashing of photoresist – mask used in IC manufacturing, using oxygen plasma mostly

• Cleaning) – active / passive (current flows through the cleaned surface or not)

• Plasma activation of surfaces (generation of radicals, grafting of functional groups, ...)

THIN FILMS EVAPORATION DEPOSITION• Low pressure – long mean free

path needed

• Heating and evaporation of material for thin film deposition

• Substrate is cold – condensation of vapors of material on substrate

• Necessityof heating up – limited by thermal resistance of the boat

• Improvement – utilization of fast electrons bombardment (e-gun)

• Similar is the thermal CVD – there is a heat needed for precursor decomposition and therefore a heat stress of substrate

Ref. Fig49

THIN FILMS EVAPORATION DEPOSITION

MAGNETRON SPUTTERING, REF. 10

• 1852: Sir William Robert Grove - cathode disintegration

• 1870s: reflective metallic coatings of mirrors

• 1923: John Thompson – term „sputtering“ – (in Czech rozprašování)

• 1970: reactive sputtering

• 1999: HiPIMS – sputtering by the pulses of (very) high power

• Advantages comparing to the evaporation deposition:

• High melting point metals deposition

• Multi-component (stechiometric) thin films

• Deposition of Oxides, Nitrides, Carbides, …

MAGNETRON SPUTTERING

Cathode

- VNeutral Vapour

Ar+ Anode

Secondary Electron Neutralized Reflected Ion

Surface Atoms

Plasma

Sputtered Atom Sputtered Atom

Incident Ion

Ref. Fig50abcd

Ref. Fig51abc

HARD PROTECTIVE COATINGS

Ref. Fig52ab

PACVD (PECVD)

Example: deposition of SiO2 from gas precursors: Si(OC2H5) + O2

• For deposition from precursor the ENERGY must be inserted to decompose the precursor

• PVD – energy is supplied in form of thermal energy (high temperature 500-900 oC)

• PECVD – energy is supplied by the plasma

• Fast electrons, excited particles etc.

• Temperature of Ions/Neutrals is low – thus no destruction of substrates

Ref. Fig53

PACVD (PECVD)

Ref. Fig54

CCP REACTOR FOR PACVD DEPOSITION

ETCHING / ASHING

Crucial steps in microelectronics manufacturing

1.Thin film deposition

2.Photo-resist deposition and exposure

3.Photo-resist etching and subsequent etching of deposited thin film

4.Photo-resist ashing (e.g. O + photo-resist-> CO2 + H2O)

5.And again 1. …

•In etching – „drilling of holes (trenches)“ is crucial to maintain strong anisotropy (aspect ratio) and etching selectivity, e.g. Si + 4Cl -> SiCl4

ETCHING / ASHING

Ref. Fig55

ETCHING / ASHING

Ref. Fig56

ETCHING / ASHING

Ref. Fig57

Ref. Fig58ab

MIRRORING SURFACES (LAYERS)

Ref. Fig59

LIGHTING

• Glow (neon) lamp – low pressure glow discharge lamps („neons“)

• Fluorescent tubes (low pressure alternating glow discharge – conversion of wavelengths using luminophores)

• Sodium lamp – glow discharge in sodium vapors – resonance doublet of sodium atomic emission lines 580 nm

Ref. Fig62

Standard Compact Fluorescent Lamp (CFL)

Fluorescent Tube - strong emission lines on background continuum

High pressure mercury (street) lamp - “white” light with a few emission lines

High pressure sodium (street) lamp - typ. orange light

AND WHAT ABOUT THE DTD DISC?

Ref. Fig63

THANK YOU FOR YOUR ATTENTION!

BASIC REFERENCES (REF.#)

1. KRACÍK, Jiří, Josef B. SLAVÍK a Jaromír TOBIÁŠ. Elektrické výboje. 1. vyd. Praha: Státní nakladatelství technické literatury, 1964. 220 s.

2. CHEN, Francis F. a Jane P. CHANG. Lecture notes on principles of plasma processing. New York: Kluwer Academic/Plenum publishers, 2003. ix, 208 s. ISBN 0-306-47497-2.

3. ROTH, Reece J. Industrial plasma engineering. Volume 2, Applications to nonthermal plasma processing. Bristol: Institute of Physics Publishing, 2001. xi, 645 s. ISBN 0-7503-0544-4.

4. ROTH, Reece J. Industrial plasma engineering. Volume 1, Principles. Bristol: Institute of Physics Publishing, 1995. xiii, 538. ISBN 0-7503-0317-4.

5. LIEBERMAN, M. A. a Allan J. LICHTENBERG. Principles of plasma discharges and materials processing. 2nd ed. Hoboken, N.J.: John Wiley & Sons, 2005. xxxv, 757. ISBN 0471720011.

6. MARTIŠOVITŠ, Viktor. Základy fyziky plazmy :učebný text pre magisterské štúdium. 1. vyd. Bratislava: Univerzita Komenského, 2006. 189 s. ISBN 80-223-1983-X.

7. GROSZKOWSKI, Janusz. Technika vysokého vakua [Groszkowski, 1981]. 1. vyd. Praha: SNTL - Nakladatelství technické literatury, 1981. 438 s.

8. http://en.wikipedia.org/wiki/Plasma_sheath

9. http://www.chm.bris.ac.uk/~paulmay/misc/msc/msc4.htm

10. Pavel Souček, přednáška na CXI TUL, Liberec 2013

EXTENDED REFERENCES,CITATIONS OF USED IMAGES (REF. FIG#)

1. a) http://hzhilong.com/markets.htm

b) http://www.acreetech.com/index.php/products/diamond-like-carbon-coating

2. http://www.shm-cz.cz/pvd-povlaky-a-sluzby/pvd-povlaky/tin/

3. http://www.pfeiffer-vacuum.net/

4. DataTresorDisc: www.datatresordisc.cz

5. http://en.memory-alpha.org/wiki/Plasma_weapon (Paramount Pictures and/or CBS Studios)

6. http://hifiland.net/katalog/ozonizer-masazni-stroj-z-filmu-postriziny~zozonizer.html

7. http://www.nasa.gov/vision/space/travelinginspace/future_propulsion.html VASIMR

8. Ji Q., A. Sy, J.W. Kwan. “Radio frequency-driven proton source with a back-streaming electron dump,” Rev Sci Instrum. 81(2):02B312 (2010).

9. http://www.shorpy.com/node/16228 Times Square:1950 author:„mpcdsp“

11. http://www.princeton.edu/~his291/Magdeburg_Spheres.html

12. Vacuum by means of a mercury column. Florence, 1644. [Cf. Torricelli 1644; Middleton 1964, pp. 23-30.]

14. Pavel Slavíček, study materials to F4160: http://is.muni.cz/el/1431/jaro2014/F4160/um/

28. IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 26, NO. 6, DECEMBER 1998 , 1685 The Atmospheric-Pressure Plasma Jet: A Review and Comparison to Other Plasma Sources Andreas Schütze, James Y. Jeong, Steven E. Babayan, Jaeyoung Park, Gary S. Selwyn, and Robert F. Hicks

29. http://www.ipp.cas.cz/Develop/Tokamak/euratom/index.php/cs/compass-diagnostiky/mikrovlnne/ece-ebw-radiometr

30. http://hobby.idnes.cz/nebezpecne-spojeni-pes-na-voditku-po-boku-muze-je-nejagresivnejsi-1cm-/hobby-mazlicci.aspx?c=A111111_112952_hobby-mazlicci_bma

31. http://www.pesweb.cz/cz/102.z-utulku-domu

32. IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 26, NO. 6, DECEMBER 1998 , 1685 The Atmospheric-Pressure Plasma Jet: A Reviewand Comparison to Other Plasma Sources Andreas Schütze, James Y. Jeong, Steven E. Babayan, Jaeyoung Park, Gary S. Selwyn, and Robert F. Hicks

34. Larryisgood: http://en.wikipedia.org/wiki/File:Zeta_Potential_for_a_particle_in_dispersion_medium.png

35. http://www2011.mpe.mpg.de/pke/PKE/Paper_THOMAS-2000/index.html (Debye shilding)

36. http://www.chm.bris.ac.uk/~paulmay/misc/msc/msc4.htm (Sheath pictures)

37. Exp. Methods and Spec. Laboratory A 2 – study materials at IS MU (is.muni.cz)

38. abc: http://www.chm.bris.ac.uk/~paulmay/misc/msc/msc4.htm (Parameters, EEDF)

41. http://www.aldebaran.cz/bulletin/2012_42_pla.php, photo there incorporated from V. A. Lisovskiy et al.: Validating the Goldstein-Wehner law for the stratified positive column of dc discharge in an undergraduate laboratory; European Journal of Physics 33/6 (2012) pp. 1537-1545

44. http://www.prf.jcu.cz/ufy/struktura/laboratore/laborator-fzyikz-plazmatu.html

45. Photo: CEPLANT

50. abcd: Pavel Souček, lecture at CXI TUL, Liberec 2013

51. abc: Pavel Souček, lecture at CXI TUL, Liberec 2013

52. ab: http://www.shm-cz.cz/

53. http://jnltech.en.ec21.com/PECVD_Plasma_Enhanced_Chemical_Vapor--4635451_4635461.html

54. R.V.Stuart: Vacuum technology Thin Films and Sputtering, Academic Press 1983 (scheme of PECVD)

55. http://asml.nl/asml/show.do?lang=KR&ctx=28145&rid=44709

56. Nanotechnology and Nanomaterials » "Updates in Advanced Lithography", book edited by Sumio Hosaka, ISBN 978-953-51-1175-7, Published: July 3, 2013 under CC BY 3.0 license

57. Nanotechnology and Nanomaterials » "Updates in Advanced Lithography", book edited by Sumio Hosaka, ISBN 978-953-51-1175-7, Published: July 3, 2013 under CC BY 3.0 license

58. ab: http://www.tf.uni-kiel.de/matwis/amat/semitech_en/kap_7/backbone/r7_2_2.html

59. W. Espe: Technologia hmot vákuovej techniky, Slovenská akadémia vied, Bratislava

61. http://danyk.cz/zdroj_vfe.html (sodium lamp)

62. http://www.zshorakhk.cz/optika/Barvy%20duhy%20II.htm (spektra)

63. www.datatresordisc.cz

Mgr. Jan Čech, Ph.D., Masarykova univerzita 19.9.2014, Brno, Vysoké učení technické v Brně...

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