Transcript Slide 1

Society of Vacuum Coaters, TechCon 2013, Providence, RI, April 22-25, 2013
Helicons are RF plasmas in a magnetic field
Density increase over ICP
Prf
200
400
600
800
1000
%
16%
21%
35%
38%
42%
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Helicon sources usually use heavy magnets
The MØRI source of Plasma Materials Technologies, Inc.
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Use permanent magnets instead
8
6
4
2
NdFeB ring magnet
3” ID, 5” OD, 1” high
0
-2
Stagnation point
The far-field is fairly uniform
-4
-6
Put plasma here
-8
-10
or here, to adjust B-field
-12
-14
-16
-10
-8
-6
-4
-2
0
2
4
6
8
10
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Single-tube setup
LANGMUIR PROBE
PERMANENT
MAGNET
HEIGHT
ADJUSTMENT
GAS FEED
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Optimized discharge tube: 2” x 2”
GAS INLET
(optional)
1. Diameter: 2 inches
2. Height: 2 inches
3. Aluminum top
5 cm
ANTENNA
4. Material: quartz
5. “Skirt” to prevent eddy currents
canceling the antenna current
5.1 cm
10 cm
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
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Experimental chamber
19 cm
6.8
Port 1
16.9
WALL MAGNETS
27.2
Port 2
38
Langmuir probes
at three ports
Port 3
46
PUMP BAFFLE AND GROUND PLANE
Gate Valve
To Turbo Pump
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A few data
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.
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Side view of an array source
165 cm
Height can be adjusted electrically if desired
Aluminum sheet
15 cm
30 cm
Z1
Probe ports
Z2
The source requires only 6” of vertical space above the
process chamber. Two tubes are shown.
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Medusa 2, an 8-tube array
3.5"
29"
7"
7"
21"
7"
7"
65"
Possible positions shown
for 8 tubes.
Tubes set in deeply (½ inch)
7"
3/4” aluminum
12"
1/2" aluminum
Endplates: gas feed and
probe port at each end.
Substrate
motion
Two arrangements of array
35.6 cm
y
17.8
Staggered array
x
53.3 cm
17.8
17.8
Covers large area
uniformly for substrates
moving in the y-direction
165 cm
Top view
53.3 cm
17.8
y
x
17.8
17.8
17.8
165 cm
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
The top gas feed did not improve
operation.
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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
3.5
3
n
KTe
-3
cm )
2.5
n (10
11
2
1.5
1
0.5
0
-25
-20
-15
-10
-5
0
r (cm)
5
10
15
20
25
Density profiles along the chamber
Staggered configuration, 2kW
Bottom probe array
5
Staggered, 2kW,
D=7", 20mTorr
Argon
n (1011 cm-3)
4
y (in.)
-3.5
0
3.5
3
2
1
0
-8
-6
-4
-2
0
2
4
6
x (in.)
8
10
12
14
16
Density profiles along the chamber
Compact configuration, 3kW
Bottom probe array
10
Compact, 3kW,
D=7", 20mTorr
y (in)
3.50
3.5
n (1011 cm -3)
8
6
Data by Humberto
Torreblanca, Ph.D.
thesis, UCLA, 2008.
4
2
0
-8
-6
-4
-2
0
2
4
6
x (in.)
8
10
12
14
16
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An 8-tube array for round substrates
Distributor
RG 393 teflon coax cable to each antenna.
No center
is necessary!
Antennas aretube
water-cooled
in pairs, so that
Antennas are 1/8" OD copper tubing.
water enters and leaves the system at ground
potential.
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Compact modules
7.00
7.00
14.00
Matching circuit
28.00
TOP VIEW OF ONE MODULE
RF in
Motor
C1
C2
Motor
END VIEW
MATCHING CIRCUIT
TOP VIEW
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The end
Thank you
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