Download Advanced magnet bar designs for rotatable magnetrons

Advanced magnet bar designs for rotatable
magnetrons
Dermot Monaghan, Gencoa, Liverpool UK
Structure of presentation
• Magnetic array features and performance
• Magnetic strengths and tuning
• IV curve examples
•Auxillary anodes, DLIM and accessories
NREL
Different magnetic and anode designs for rotatable magnetrons based upon needs
One solution does not fit all for production!
RF
Lower strength for RF power modes
HSS
High Strength Single for thicker targets or
lower discharge voltages
SS-TCO
Single cathode magnetics with active anode
for reduced resistivity TCO layers for DC and
DC pulsed operation
DLIM
Double cathode Low Impedance magnetics
for high rate reactive deposition of oxides
with low substrate plasma interference
(patent pending)
DLIMTCODC
Double cathode low TCO resistivity
magnetics for DC powered double
magnetrons with an additional active anode
(patent pending)
DLIMTCOMF
Double cathode low TCO resistivity
magnetics for medium frequency (MF)
powered double magnetrons (patent
pending)
All magnetic designs are carefully optimized to provide high target use and
optimum plasma and layer properties
This shows a
standard
magnetic field for
a single cathode
Uniform erosion of target with minimum re-deposition, Al2O3 process
Erosion to the target ends to for metallic mode
Magnetic field prevents plasma interactions with substrates
High T-S lowers electron damage of layers
Plot of magnetic field strength relative to distance from the target backing tube
Parallel vector to surface at centre of the race-track
Gencoa Magnetic Bars have unique tuning options for local variations of strength
Unlimited in terms of flexibility and ease
600
BZ [FLUXU]
BY [FLUXU]
BX [FLUXU]
400
200
0
0
-200
-400
-600
-800
5
10
15
20
25
Gencoa Magnetic Bars have unique tuning options for local variations of strength
Unlimited in terms of flexibility and ease
600
BZ [FLUXU]
BY [FLUXU]
BX [FLUXU]
400
200
0
0
-200
-400
-600
-800
5
10
15
20
25
Gencoa Magnetic Bars have unique tuning options for local variations of strength
Unlimited in terms of flexibility and ease
600
BZ [FLUXU]
BY [FLUXU]
BX [FLUXU]
400
200
0
0
-200
-400
-600
-800
5
10
15
20
25
Magnetics are encapsulated for thermal stability and against degradation
Angle adjustment possible on all end-block models
Magnet bars are scanned in 3D for quality control
Magnetic components actively cooled to limit temperature rise to < 1ºC
Prevents field variations due to water temp rises.
Optionally high uniformity magnetic packs are available to 1% tolerance
within the linear magnetic region
300
TrackA
250
Gauss
200
TrackB
Average A-B
Top lim (+1%)
150
100
50
Bot Lim (-1%)
Top lim +2% in
lenght
Bot lim -2% in
lenght
Top bound+1% ave
0
-400
-300
-200
-100
0
100
Position (mm)
200
300
400
Standard single TR magnetron magnetic array current / voltage characteristics
475 mm long Al target, 0-10kW DC power
20
18
16
14
I, A
12
10
2 mTorr
5 mTorr
10 mTorr
Poly. (2 mTorr)
Poly. (5 mTorr)
Poly. (10 mTorr)
8
6
4
2
0
340
360
380
400
420
U, V
440
460
480
500
RF mode single TR magnetron magnetic array current / voltage characteristics
475 mm long Al target, 0-10kW DC power
22
2 mTorr (RF)
20
5 mTorr (RF)
18
10 mTorr (RF)
16
Poly. (2 mTorr (RF))
Linear (5 mTorr (RF))
I, A
14
Linear (10 mTorr (RF))
12
10
8
6
4
2
0
300
350
400
450
500
U, V
550
600
650
DLIM magnetics dual magnetron DC:DC power current / voltage characteristics
475 mm long Al target, 0-15kW DC each target
35
2mTorr
30
5mTorr
10mTorr
25
Poly. (5mTorr)
Poly. (2mTorr)
Poly. (10mTorr)
I, A
20
15
10
5
0
340
360
380
400
420
440
U, V
460
480
500
520
DLIM magnetics dual magnetron AC power current / peak voltage characteristics
475 mm long Zn:Al target no O2, 0-8kW AC power
10
2mTorr
5mTorr
10mTorr
8
Expon. (10mTorr)
Expon. (5mTorr)
I, A
Poly. (2mTorr)
6
4
2
0
450
500
550
600
650
U, V
700
750
800
850
Advice is given on recommended layouts for different process types and applications
e.g. locations of gas bars and gas zones with P.E.M.
Supplementary magnetic anodes for rotatable cathodes with DC & DC pulsed power
More stable environment to avoid process drifts
The introduction of an optional
magnetically guided hidden auxiliary
anode and gas bar offers the following
benefits:
• reduced substrate movement influence
on the plasma impedance
• lower discharge voltages – lower
impedance – lower TCO resistivity
• less drift of plasma impedance and
instability for non-conducting layers
• more consistent uniformity
• lower plasma heating of the substrate
• gas injected uniformly and protects
hidden anode surface
Gas bar options and magnetically guided anodes are available to further enhance
the performance of your process
Lower impedance ‘linked’ magnetics
Key to low defect reactive sputtering of oxides
Plasma to substrate interaction by assymetric magnetics and tilting
New Gencoa patent
Electron trajectories between the 2 cathodes determine the spread of plasma
Tuned for different process requirements
Angle and
magnetic design
can be modelled
accurately to
reduce or
enhance plasma
interaction with
the glass
Plasma control by Double Low Impedance Magnetics - DLIM
Adjustment of angle relative to substrate position
This shows a
typical DLIM
design for
reactive SiO2,
TiO2 Nb2O5, AZO
and ITO
Gencoa single rotatable magnetics offer many advantages
Optional anodes further expands the process windows
• Low voltage sputtering – thick targets up to 20mm
• Target erosion right to the end of the target – no redeposit
• High target use > 75% guaranteed for flat metallic targets on 152mm
OD at less than 5mTorr pressures
• Magnetics protected from the water cooling via stainless steel
encapsulation for long term stability – Helium leak checked
• Magnetics actively cooled to reduce magnetic strength variation
down the target tube due to a rising water temperature
• High uniformity by mechanical design of the magnetic array, preselected magnets and magnetic mapping
• High pressure operation with RF magnetic pack or via shunting of the
standard magnetics turn-around region
Gencoa DLIM have now begun a highly successful market entry
DLIM have proved better than standard magnetics
• Defect free, low damage reactive Al2O3 layers for ultra-gas barriers –
glass and web substrates.
• High rate, reactive TCO’s for solar cells - large scale rotatable based
production machines for TCO on glass for solar cells – departure from
the standard ceramic target based approach.
• Reactive rotatable based multi-component cermet layers on 4.5m
long solar collectors – lower voltage operation allowing higher rates
and less plasma disturbance as substrates move past.
• DLIM provide easier reactive process control – lower fluctuation in
PEM and target voltage signal as glass passes.
• DLIM provide better uniformity – lower plasma interaction and
electrostatic charge effects on glass.