society of vacuum coaters, techcon 2013, providence, ri, april 22-25, 2013
TRANSCRIPT
Society of Vacuum Coaters, TechCon 2013, Providence, RI, April 22-25, 2013
Helicons are RF plasmas in a magnetic field
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Prf %
200 16%
400 21%
600 35%
800 38%
1000 42%
Density increase over ICP
Helicon sources usually use heavy magnets
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The MØRI source of Plasma Materials Technologies, Inc.
Use permanent magnets instead
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-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
-10 -8 -6 -4 -2 0 2 4 6 8 10
NdFeB ring magnet3” ID, 5” OD, 1” high
Stagnation point
Put plasma here
or here, to adjust B-field
The far-field is fairly uniform
Single-tube setup
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Optimized discharge tube: 2” x 2”
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1. Diameter: 2 inches
2. Height: 2 inches
3. Aluminum top
4. Material: quartz
5. “Skirt” to prevent eddy currents canceling the antenna current
5.1 cm
10 cm
5 cmANTENNA
GAS INLET (optional)
The antenna is a simple loop, 3 turns for 13 MHz, 1 turn for 27 MHz. The antenna must be as close to the exit aperture as possible.
Antenna: 1/8” diam tube, water-cooled
Experimental chamber
UCLAGate Valve
To Turbo Pump
PUMP BAFFLE AND GROUND PLANE
WALL MAGNETS
Port 1
Port 3
Port 2
38
46
6.8
16.9
27.2
19 cm
Langmuir probes at three ports
A few data
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Radial density profiles at the 3 ports
Low temperature at Port 3
Center density vs. RF power at Port 1
Note that a high B-field does not match this density range.
Side view of an array source
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165 cm
30 cm
15 cm
Probe ports
Aluminum sheetHeight can be adjusted electrically if desired
The source requires only 6” of vertical space above the process chamber. Two tubes are shown.
Z1
Z2
65"
21"
7"
7"
7"
7"29"
3.5"
12"
7"3/4” aluminum
Endplates: gas feed and probe port at each end.
Tubes set in deeply (½ inch)
1/2" aluminum
Medusa 2, an 8-tube array
Possible positions shown for 8 tubes.
Substrate motion
Two arrangements of array
Staggered array
Covers large area uniformly for substrates moving in the y-direction
165 cm
53.3 cm
17.8
17.8
17.8
35.6 cm
x
y
165 cm
53.3 cm
17.8
17.8
17.8
x
yTop view 17.8 Compact array
Gives higher density, but uniformity suffers from
end effects.
Operation with cables and wooden magnet tray
It’s best to have at least 3200W (400W per tube) to get all tubes lit equally.
An adjustable wooden magnet tray
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The top gas feed did not improve operation.
A rectangular 50 transmission line
50-W line with ¼” diam Cu pipe for cooled center conductor
Operation with rectangular transmission line
Radial profile between tubes at Z2
0
0.5
1
1.5
2
2.5
3
3.5
-25 -20 -15 -10 -5 0 5 10 15 20 25r (cm)
n (1
01
1 c
m-3
) n
KTe
Density profiles along the chamber
Staggered configuration, 2kW
Bottom probe array
0
1
2
3
4
5
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16x (in.)
n (1
011 c
m-3
)
-3.5
0
3.5
Staggered, 2kW, D=7", 20mTorr
y (in.)
Argon
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Density profiles along the chamber
Compact configuration, 3kW
Bottom probe array
0
2
4
6
8
10
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16
x (in.)
n (
10
11 c
m-3
)
3.5-03.5
Compact, 3kW, D=7", 20mTorr
y (in)
Data by Humberto Torreblanca, Ph.D. thesis, UCLA, 2008.
An 8-tube array for round substrates
UCLANo center tube is necessary!
Compact modules
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END VIEW
Matching circuit
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The end
Thank you
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