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Plasma chemistry and film growth in a complex organic system

Plasma chemistry and film growth in a complex organic system. 1 MJ Goeckner, 1 C Estrada-Raygoza, 1 G Padron-Wells, 1 P.L.S. Thamban, 1 L.J. Overzet, 2 M. Senike and 2 M. Hori. 1 University of Texas at Dallas 2 Plasma Nanotechnology Center (Plant), Nagoya University. Motivation.

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Plasma chemistry and film growth in a complex organic system

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  1. Plasma chemistry and film growth in a complex organic system 1MJ Goeckner, 1C Estrada-Raygoza, 1G Padron-Wells, 1P.L.S. Thamban, 1L.J. Overzet, 2M. Senike and 2M. Hori 1University of Texas at Dallas 2 Plasma Nanotechnology Center (Plant), Nagoya University

  2. Motivation Plasma Polymerized Parylene C High adhesion! (UTD data) ClpX precursor for Parylene C Adhesion lifetimes Protective layer 1 hour, standard parylene 85 hrs, PE-Parylene Lactated Ringer’s solution @ 100 C 8 hrs, standard parylene Implants MEMs 176 hrs, PE Parylene Lactated Ringer’s solution @ 20 C Bienkiewicz, Med. Dev. Technol., January/February (2006) 10-11.

  3. Goal: Control of film properties Objective: Prediction and control of film properties. Strategy: Understand how plasma chemistry affects both film formation and polymerization. Electrical System Plasma phase Plasma Vaccum system Pressure, Power Flow rate, chuck temperature Wall conditioning Surface

  4. 1 Plasma operational variables vs. plasma chemistry? Plasma operational variables vs. film growth/properties? 2 Plasma chemistry vs. film growth/polymerization? 3 How to tackle this challenge? Relate the plasma chemistry with film formation and plasma polymerization processes Goal:

  5. 1 Plasma operational variables vs. plasma chemistry? Plasma operational variables vs. film growth/properties? 2 Plasma chemistry vs. film growth/polymerization? 3 How to tackle this challenge? Relate the plasma chemistry with film formation and plasma polymerization processes Goal:

  6. Operational variables and key variables • Operational Variables: • Time of the discharge • Pressure • RF power • Flow rate • Walls of reactor • Film substrate • Chuck temperature • Key variables: • Interaction time • Density of particles • Energy to break bonds • Residence time (Probability for collisions) • Heterogeneous reactions • Adsorption/desorption mechanisms. • Adsorption/desorption Gas phase Surface

  7. Dissociation FTIR Identify Plasma chemistry + + Quantify Excitation & Ionization OES (e-beam) Plasma chemistry and operational variables • Operational Variables: • Pressure • RF power • Flow rate Plasma chemistry Electrical System Species densities Plasma Vaccum system

  8. Identification of major species - FTIR Wavenumber (cm-1)

  9. Identification of major species – Direct OES

  10. Summary: plasma species identification Dissociation FTIR + OES and OES e-beam Excitation & Ionization HCl H2 C2H2 Cl2 CH4 H, Cl, CH HCl+ CH+ Plasma Neutrals Radicals Ions

  11. 1.0 40 80 120 160 PT=60mTorr 0.5 2ClpX C2H2 x20 Ni/N60mTorr CH4 x20 HCl 1.0 PT=7.5mTorr 2ClpX 0.5 Ni/N7.5mTorr C2H2 x20 HCl 0.0 40 80 120 160 Quantification of neutral major species by FTIR Plasma chemistry is strongly affected by pressure nClpx + nHCl⇒ 0.6 nTotal nClpx + nHCl⇒ nTotal Energy (eV/molec)

  12. OES main chamber OES disadvantage: Cl2 + 2ClpX* Cl2 Absolute density calculation not trivial CH Cl2+ or C4H2+ Ha HCl+ Hb Cl H2 CH Cl2 Ar HCl+ Ebeam tool is possible * Ha Hb OES ebeam CH Cl Cl2 H2 OES emission spectroscopy vs e-beam OES * P.L.S. Thamban, J. Hosch, M.J. Goeckner, Rev. Sci. Instrum. 81 (2010) 013502.

  13. Electron impact disociative excitation of chloro-p-xylene Electron impact disociative excitation of ClpX Electron impact disociative excitation of chlorobenzene HCl+ 250 300 350 400 450

  14. Radical information by e-beam OES HCl+ benzyl 305 300 350 250 Red shift from benzyl 316.5 nm 310 nm

  15. GEC E-beam on Ha HCl+ Hb Cl2 CH CH e-beam OES tracking of species Goal: Observation of the trends for of excited species in plasma on P.L.S. Thamban, J. Hosch, M.J. Goeckner, Rev. Sci. Instrum. 81 (2010) 013502.

  16. Challenges for absolute density calculation: 1) High deposition on electron source walls 2) High dielectric deposition on Faraday Cup Ebeam FTIR HCl+ relation with main chamber HCl density

  17. Plasma operational variables vs. plasma chemistry? 1 Plasma chemistry vs. film growth/polymerization? Plasma operational variables vs. film growth/properties 3 2 How to tackle this challenge? Relate the plasma chemistry with film formation and plasma polymerization processes Goal:

  18. Plasma discharge effect in film properties Solid film High pressure Film formation Low pressure Condensation of monomer Evaporates in a few hours EXCELLENT adhesion Oily film High pressure Evaporating for 8 months Plasma No plasma Film properties Plasma processing conditions Plasma Chemistry?

  19. Plasma chemistry vs Film formation Solid film W (J/s) F (molec/s) Low pressure Kinetic regime 60mTorr EXCELLENT adhesion 30mTorr Intermediate pressure High Power Solid film 15mTorr Oily film 7.5mTorr High pressure Mass transport regime Evaporating for 8 months Monomer eV/molec 0, 3.1, 9.2, 27.5, 76.4, 152.9

  20. Plasma Parylene C films IRRAS s polarization Normalized Intensity (cps) **Characterization done at Hori-Sekine Lab at University of Nagoya

  21. Plasma operational variables vs. plasma chemistry? Plasma operational variables vs. film growth/properties? 1 2 Plasma chemistry vs. film growth/polymerization? 3 How to tackle this challenge? Relate the plasma chemistry with film formation and plasma polymerization processes Goal:

  22. Plasma monomer density effect in film growth 100 W 50 W 18 W 2 W ClpX polymerization is a surface reaction

  23. Monomer concentration vs Film growth/polymerization Monomer density in the plasma is affecting film growth

  24. Chuck Temperature vs Film growth Reaction controlled Tchuck=50 C Tchuck=23 C Tchuck=40 C For gas CVD process Mass transfer controlled

  25. Polymerization mechanism? CVD Par C Plasma Par C ? Polymer X Monomer + HCl 60-99% HCl H2 C2H2 Cl2 CH4 H, Cl, CH HCl+ CH+ Plasma Plasma

  26. Polymerization mechanism? CVD Par C Plasma Par C ? HCl H2 C2H2 Cl2 CH4 H, Cl, CH HCl+ CH+ Plasma

  27. Polymerization mechanism? • 1. Precursors formation: • Gas phase • Surface • 2. Polymerization • Initiation • Propagation • Termination Free radicals? Ionic?

  28. Ion bombardment Ion bombardment Silicon cover Sample Polymerization of PACVD Parylene C is IONIC

  29. Summary Plasma chemistry is directly related to the film deposition and polymerization processes. Plasma CVD is capable of producing textured and crystalline polymer films.

  30. Ackowdledgements Verity Instruments specially Dr. Jimmy Hosch Hori-Sekine Lab group at University of Nagoya, specially Prof. Hori and Prof. Ishikawa Aichi Science and Technology Foundation This work was funded by CONACYT (Mexico), the US National Science Foundation and Verity Instruments. This material is based upon work supported by the National Science Foundation under Grant No. CBET 1129395.Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

  31. Thank you for your attention Questions?

  32. Plasma polymerization of Parylene C PA CVD polymer CVD polymer • Increased adhesion to several substrates • Selective deposition • Texture control • Film properties not compromised

  33. Why Plasma Assisted CVD? HT Parylene SELECTIVE PARYLENE C DEPOSITION Silicon, Glass, TiO2 NaCl PEN Au, Al, Stainless Steel Excellent adhesion to Polymer film Not extensive surface cleaning. No pre-treatment for optimal adhesion Bad adhered film

  34. Ongoing Work • Ionization & excitation processes? • Quantification of radicals (H, Cl, CH) • Polymerization mechanism?

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