http://www.surfacetreatments.it/thinfilms Cylindrical Post-Magnetron sputtering for High Rate Niobium deposition (Cristian Pira - 15') Speaker: Cristian Pira - INFN-LNL | Duration: 15 min. Abstract 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.

1. CylindricalPost-Magnetron Sputteringfor High Rate Niobium deposition Cristian Pira

2. CERN standard configuration Is it perfect? 2 Important limitations for the target: Not punctual source Technological limits

3. Punctual Source > 28 ° R. Losito, CERN SL-Note-98-008, February 1998 R. Losito, CERN SL-Note-2000-047 CT, July 2000

5. Low Target Consumption

6. Bad Target Cooling

8. Why High Rate Sputtering? Decreasesimpurities in film growth fi= fractionofimpuritiesof i species Ni = Numbersof i species i= Stikingfactorof i species R = Deposition Rate L. I. Maissel, R. Glang, Handbook of thin film technology, Mc Graw-Hill, 1970

9. B B coil CylindricalVS Post Magnetron

10. AbnormalGlowDischarge ThermionicEmission ThermionicEmission

11. CathodeSection Vacuum Ceramic Feedthrough Potential Tube Grounded Tube Shield BN Insulator CF100 Flange BN Insulator Water tube Allumina Pipe Nb tube Post Magnetron

12. Cathode

13. High Rate Sputtering System

14. High Rate Sputtering System

15. Samplesholder 4 5 3 6 7 2 8 1

16. SputteringConditions Base Pressure 210-9mbar PAr = 710-3mbar I = 15 – 20 A V  250 V t =15 min T cavity = 200-300 °C Deposition Rate = 2,5 nm/s

17. I-V Characteristics

18. Thickness

19. Open Wing Post Magnetron

20. GrainSize Cilyndrical Magnetron ~ 15 nm Post Magnetron > 25 nm

21. RRR 4<RRR<9

22. Tc Tc < 9,26 K

24. Bombardmentofcavitywallbyelectrons?

26. Cavitydegassing?

27. Bombardmentofcavitywallbyelectrons?

30. Dipendenza degli orientamenti dalla posizione della cavità

31. Si ottiene una figura polare di punti (,) con curve che collegano punti di uguale intensità.

33. Deposition Angle Influence Tonini et al., LNL Annual Report 2004

36. P VS T 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)