Pira - Cylindrical post magnetron sputtering


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Cylindrical Post-Magnetron sputtering for High Rate Niobium deposition (Cristian Pira - 15')
Speaker: Cristian Pira - INFN-LNL | Duration: 15 min.
The use of Nb/Cu cavity at CERN for the LEP and at the INFN-LNL for Alpi Linac has demonstrated the possibility to use this technology for particles accelerators to substitute the more expensive technology of niobium bulk cavity. The limit of the Nb/Cu cavity is the Q-slope, which decreases the Q factor at high accelerating fields. The accelerators community supposes that it’s possible to eliminate, or to decrease, the problem of Q-slope with high pure films of sputtered niobium. One way to obtain pure films is to decrease the number of impurities enclosed in the growing film.
It’s possible to reduce the number of impurities when the sputtering rate process increases.
We study the possibility to enhance the plasma density in order to increase the sputtering rate and then reduce the impurities in the niobium sputtered film and finally obtain high pure films.
In order to enhance the plasma density we sputter the niobium target with high currents to heat it and get to thermoionic emission. This sputtering method is called high rate sputtering.
First results of Niobium coatings will be presented.

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Pira - Cylindrical post magnetron sputtering

  1. 1. CylindricalPost-Magnetron Sputteringfor High Rate Niobium deposition<br />Cristian Pira<br />
  2. 2. CERN standard configuration<br />Is it perfect?<br />2 Important limitations for the target:<br />Not punctual source<br />Technological limits<br />
  3. 3. Punctual Source<br />> 28 °<br />R. Losito, CERN SL-Note-98-008, February 1998 <br />R. Losito, CERN SL-Note-2000-047 CT, July 2000<br />
  4. 4. Technologicallimits<br /><ul><li>Longitudinal Electron BeamWelding
  5. 5. Low Target Consumption
  6. 6. Bad Target Cooling
  7. 7. Difficultytoempty the Nb/Steel air space</li></li></ul><li>Project Goal<br /><ul><li>Eliminate the technologicallimits</li></ul>of CERN cathode<br /><ul><li>Realize a punctual source</li></ul>Low Target Area<br />
  8. 8. Why High Rate Sputtering?<br />Decreasesimpurities in film growth<br />fi= fractionofimpuritiesof i species<br />Ni = Numbersof i species<br />i= Stikingfactorof i species<br />R = Deposition Rate<br />L. I. Maissel, R. Glang,<br />Handbook of thin film technology, Mc Graw-Hill, 1970<br />
  9. 9. B<br />B<br />coil<br />CylindricalVS Post Magnetron<br />
  10. 10. AbnormalGlowDischarge<br />ThermionicEmission<br />ThermionicEmission<br />
  11. 11. CathodeSection<br />Vacuum Ceramic Feedthrough<br />Potential<br />Tube<br />Grounded Tube Shield<br />BN<br />Insulator<br />CF100<br />Flange<br />BN<br />Insulator<br />Water tube<br />Allumina Pipe<br />Nb tube<br />Post Magnetron<br />
  12. 12. Cathode<br />
  13. 13. High Rate Sputtering System<br />
  14. 14. High Rate Sputtering System<br />
  15. 15. Samplesholder<br />4<br />5<br />3<br />6<br />7<br />2<br />8<br />1<br />
  16. 16. SputteringConditions<br />Base Pressure 210-9mbar<br />PAr = 710-3mbar<br />I = 15 – 20 A<br />V  250 V<br />t =15 min<br />T cavity = 200-300 °C<br />Deposition Rate = 2,5 nm/s<br />
  17. 17. I-V Characteristics<br />
  18. 18. Thickness<br />
  19. 19. Open Wing Post Magnetron<br />
  20. 20. GrainSize<br />Cilyndrical<br />Magnetron<br />~ 15 nm<br />Post Magnetron<br />> 25 nm<br />
  21. 21. RRR<br />4<RRR<9<br />
  22. 22. Tc<br />Tc < 9,26 K<br />
  23. 23. Why?<br /><ul><li>Cavitydegassing?
  24. 24. Bombardmentofcavitywallbyelectrons?
  25. 25. DiffusionofSilicon or Oxigen</li></ul>from the quartzto the film?<br /><ul><li>Target poisoning?
  26. 26. Cavitydegassing?
  27. 27. Bombardmentofcavitywallbyelectrons?
  28. 28. DiffusionofSilicon or Oxigen</li></ul>from the quartzto the film?<br /><ul><li>Target poisoning?</li></li></ul><li>thanks for the attentionand for any help<br />cristian.pira@lnl.infn.it<br />
  29. 29. Tessiture<br /><br /><br /><ul><li>Verifica l’esistenza di orientamenti preferenziali
  30. 30. Dipendenza degli orientamenti dalla posizione della cavità
  31. 31. Si ottiene una figura polare di punti (,) con curve che collegano punti di uguale intensità.
  32. 32. I risultati sono tutti riferiti al picco (110)</li></li></ul><li>RRR VS Sputtering Angle<br />Tonini et al., LNL Annual Report 2004<br />
  33. 33. Deposition Angle Influence<br />Tonini et al., LNL Annual Report 2004<br />
  34. 34. Texture<br />RUN CERN1<br />RUN CAV4 (Regime di emissione termoelettronico)<br />RUN CAV5 (Regime di emissione termoelettronico)<br />RUN CAV3 (Regime di Abnormal Glow Discharge)<br />POSIZIONE NELLA CAVITÀ<br />POSIZIONE NELLA CAVITÀ<br /><ul><li>CERN  growingparallelto the surface
  35. 35. HR  growingparallelwith the presenceofangulargrowing</li></li></ul><li>ReticularParameter<br />Compressive stress<br />
  36. 36. P VS T<br />John A. Thornton, “Coating Deposition by Sputtering”, Hanbook of plasma processing technology, Stephen M. Rossagel, Jerome J. Cuomo and William D. Westwood eds, Noyes Publications, 196, (1990)<br />