pira - cylindrical post magnetron sputtering
DESCRIPTION
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.TRANSCRIPT
CylindricalPost-Magnetron Sputtering
for High Rate Niobium deposition
Cristian Pira
Cristian Pira 4 October 2010
CERN standard configuration
Is it perfect?
2 Important limitations for the target:
1) Not punctual source2) Technological limits
Cristian Pira 4 October 2010
Punctual Source
> 28 °
R. Losito, CERN SL-Note-98-008, February 1998 R. Losito, CERN SL-Note-2000-047 CT, July 2000
Cristian Pira 4 October 2010
Technological limits
• Longitudinal Electron Beam Welding
• Low Target Consumption
• Bad Target Cooling
• Difficulty to empty the Nb/Steel air
space
Cristian Pira 4 October 2010
Project Goal
• Eliminate the technological limitsof CERN cathode
• Realize a punctual source
Low Target Area
Cristian Pira 4 October 2010
Why High Rate Sputtering?
Decreases impurities in film growth
RN
Nf
ii
iii
fi = fraction of impurities of i species
Ni = Numbers of i speciesi = Stiking factor of i speciesR = Deposition Rate
L. I. Maissel, R. Glang,Handbook of thin film technology, Mc Graw-Hill, 1970
Cristian Pira 4 October 2010
coil
B B
Cylindrical VS Post Magnetron
Cristian Pira 4 October 2010
Abnormal Glow
DischargeThermionic Emission
Thermionic Emission
Cristian Pira 4 October 2010
Cathode Section
BNInsulator
Grounded Tube
Shield
Water tube
PotentialTube
Vacuum Ceramic
Feedthrough
CF100FlangeBN
Insulator
Allumina Pipe
Post Magnetron
Nb tube
Cristian Pira 4 October 2010
Cathode
Cristian Pira 4 October 2010
High Rate Sputtering System
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High Rate Sputtering System
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Samples holder
1
2
34 5
6
7
8
Cristian Pira 4 October 2010
Sputtering Conditions
Base Pressure 210-9 mbarPAr = 710-3 mbar
I = 15 – 20 AV 250 Vt =15 minT cavity = 200-300 °CDeposition Rate = 2,5 nm/s
Cristian Pira 4 October 2010
I-V Characteristics
0 2 4 6 8 10 12 14 16 18 20250
300
350
400
450
500
550
600
650
P = 7*10-3 mbar
V
(V
olt
)
I (Ampere)
Cristian Pira 4 October 2010
1 2 3 4 5 6 7 8
0.0
0.5
1.0
1.5
2.0
2.5
3.00
.5
0.5
1.6
1.4
0.4
0.7
0.7
0
0.9
2
1.5
9
1.7
0
1.4
4
0.6
5
0.8
7
0.5
6
0.7
1
0.9
6
1.2
6
1.3
6
0.9
2
1.0
4
1.1
6 1.5
6
2.4
7
2.0
9
2.1
0 2.5
7
1.8
6
1.5
1
1.2
9
1.0
6
1.7
7
2.4
2
2.0
1 2.3
1
1.1
8
1.2
81.6
4 2.1
7 2.5
5
2.5
6
1.8
9
1.6
2
1.6
6
Film Thickness
Cav1
Cav2
Cav3
Cav4
Cav5
Cav6
Cavity Position
mm
Thickness
Cristian Pira 4 October 2010
Open Wing Post Magnetron
Cristian Pira 4 October 2010
Grain Size15
,70
15,3
0 22,6
0
15,4
5
19,1
5
17,7
0
18,6
1
18,6
6
22,3
5
23,6
3
23,0
1
28,4
4
26,7
3
24,6
3
27,1
1
26,6
5
25,7
0
26,1
1
25,9
6
31,4
9
0,00
5,00
10,00
15,00
20,00
25,00
30,00
35,00
1 2 3 4
nm
Cavity Position
Grain Size
CERN1
Cav3
Cav4
Cav5
Cav6
32
41
Cilyndrical
Magnetron
~ 15 nm
Post Magnetron
> 25 nm
Cristian Pira 4 October 2010
RRR
5,0
7,5
4,6
4,2
5,7 6,0 6,3
9,0
5,0
6,5
6,2
7,7
4,2 5,
4 5,9 6,5
0,0
2,0
4,0
6,0
8,0
10,0
1 2 3 4
RRR
Cavity Position
RRR
Cav3
Cav4
Cav5
Cav6 32
41
4<RRR<9
Cristian Pira 4 October 2010
Tc
9,1
2
9,1
8
9,1
6
9,2
0
9,2
0
9,2
2 9,3
0
9,3
4
9,1
6
9,1
4
9,1
5 9,2
6
9,0
9
9,0
9
9,0
7
9,1
2
8,70
8,80
8,90
9,00
9,10
9,20
9,30
9,40
1 2 3 4
Tc (K)
Posizione nella cavità
Tc
Cav3
Cav4
Cav5
Cav6 32
41
Tc < 9,26 K
Cristian Pira 4 October 2010
Why?
• Cavity degassing?
• Bombardment of cavity wall by
electrons?
• Diffusion of Silicon or Oxigenfrom the quartz to the film?
• Target poisoning?
• Cavity degassing?
• Bombardment of cavity wall by
electrons?
• Diffusion of Silicon or Oxigenfrom the quartz to the film?
• Target poisoning?
Cristian Pira 4 October 2010
RRR VS Sputtering Angle
Tonini et al., LNL Annual Report 2004