UCLA Optimization of Source Modules in ICP-Helicon Multi-Element Arrays for Large Area Plasma Processing John D. Evans & Francis F. Chen UCLA Dept of Electrical Engineering LTPTL - Low Temperature Plasma Technology Laboratory AVS 2002 , Denver, Co, November 4, 2002 ELECTRO STATIC CHUCK W AFER PERM ANENT M AG NET ARRAY
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UCLA Optimization of Source Modules in ICP-Helicon Multi-Element Arrays for Large Area Plasma Processing John D. Evans & Francis F. Chen UCLA Dept of Electrical.
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UCLA
Optimization of Source Modulesin ICP-Helicon Multi-Element Arrays for
Large Area Plasma Processing
John D. Evans & Francis F. Chen
UCLA Dept of Electrical Engineering
LTPTL - Low Temperature Plasma Technology Laboratory
AVS 2002, Denver, Co, November 4, 2002
ELECTROSTATIC CHUCK
WAFER
PE
RM
AN
EN
T M
AG
NE
T A
RR
AY
UCLA
ELECTROSTATIC CHUCK
WAFER
PE
RM
AN
EN
T M
AG
NE
T A
RR
AY
Conceptual multitube m=0 helicon source for large area processing
UCLAUCLAOne-tube configuration using large-area Bo-field
coils and radially scannableLangmuir probes
QUARTZ TUBE
PVC PIPE
ANTENNA
MAGNET WINDING
7 cm
5 cm
13 cm
BNC connector
5 mm
17 mm
1 cm
1 cm
10 cm
COIL COIL
Single source tube with individual solenoidal Bo
UCLAUCLASchematic proof of low-field Helicon mode; RH-t-III antenna
Helicity pitch sense B up (down) launches m=+1 up (down) Np and VL enhanced in region that m=+1 mode propagates towards
B m = -1
m = +1
B m = +1
m = -1
UCLA
RH 1/2-helical antenna
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)N
(10
11cm
-3)
down
up
B direction
Dependence of N(B) on the direction of B reverses when the sense of the helicity of the antenna is reversed; thus it is
m = +1 helicon mode
Sense of helicity
“LH” “RH”
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)
N (1
011
cm-3
)
up
down
B direction
LH 1/2-helical antenna
Experimental evidence: Half-helical antennas launch m = +1Helicon mode from source tube when “low field peak” is present.
UCLA
Verification of Low-field Helicon Excitation
Low-field “peak” in N vs B plot
Dependence of occurrence of peak on B-field direction
Dependence of N vs B on B-direction reverses with antenna helicity
UCLA
Low-field peak increases, broadens and shifts to higher B at higher Po.
Po = 25 mTorr
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)
N (1
011
cm-3
)
down
up
B direction
Po = 10 mTorr
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)
N (1
011
cm-3
)downup
B direction
Po = 5 mTorr
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)
N (1
011
cm-3
)
down
up
B direction
Po = 1 mTorr
0
2
4
6
8
10
0 50 100 150 200 250
B (Gauss)
N (1
011
cm-3
)
down
up
B direction
UCLAUCLALeft Hand (LH) Helical Antenna Nomenclature Defined
Lant = Physical length of active antenna element
ant = Antenna Wavelength - pitch of helical straps
Half Helix
Lant = 10 cm
ant = 20 cm
Full Helix
Lant = 10 cm ant = 10 cm
2Double Helix
ant = 5 cmLant = 10 cm
UCLA
Radial Np profiles for 3 RH-helical antennas
1kW, 13.56MHz, 15mT Ar, 150G, z=3cm, next slide
Same antenna length, but different “antenna wavelengths”