Oerlikon PVD production solution for
in-situ large scale deposition of PZT
2nd International Workshop on Piezoelectric MEMS
Materials - Processes - Tools - Devices
Lausanne, 06./07.09.2011
M. Kratzer, L. Castaldi and B. Heinz
D. Kaden, H.J. Quenzer
A. Mazzalai, S. Harada, P. Muralt
Oerlikon Systems R&D, Liechtenstein
Fraunhofer ISIT, Germany
EPFL, Switzerland
Agenda
§ piezoVolume project
§ Sputter equipment
§ Key hardware factors
§ Results of in-situ PZT deposition process
§ Summary and outlook
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
EU project “piezoVolume”
Sputter cooperation and goals
Development of automated high
volume sputter system
M. Kratzer, L. Castaldi and B. Heinz
F. Tyholdt - 14:00
FP7 piezoVolume
Process development
D. Kaden and H.J. Quenzer
Process development
A. Mazzalai, S. Harada and P. Muralt
Overview
Goal of this cooperation is to develop in-situ PZT processes on a Oerlikon
sputter system which meet commercial production requirements
Project
goals
High quality PZT films on 8” substrates
§ Dielectric constant ~ 1200 and dielectric loss tanδ < 0.03
§ Piezoelectric coefficients d33,f > 100pm/V and - e31,f > 14 C/m2
§ Thickness uniformity < ± 5% at max. thickness 4 - 5 µm
§ Throughput > 3.6 wafer/hr·µm (= 1nm/s)
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
Equipment for PZT in-situ sputtering
RF magnetron sputtering from single ceramic target
CLN200 sputter tool
RF sputter module equipped with
8” Very Hot Chuck
Robot
handling
D
Support stations
Aligner (A)
Degasser (D)
Cooler (C)
A
C
Loadlocks
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
Key hardware factors
Overview
Anode & Shieldings
RF cathode
PZT sputter equipment
Heated chuck
RF Bias &
master oscillator
Magnet array & Target
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
Key hardware factors
Very Hot Chuck
Heated substrate holder for 6” and 8” wafer enable deposition
process in the temperature range needed for in-situ sputtered
PZT films
6” Very Hot Chuck
Temperature sense w afer vs. Heater set point
(6" and 8" Very Hot Chuck)
650
6" wafer
Temperature_sense wafer [°C]
600
8" wafer
550
8” Very Hot Chuck
500
450
Operational
range
400
350
450
500
550
600
650
700
750
800
850
He ate r se t point [°C]
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
Key hardware factors
Temperature uniformity 8” Very Hot Chuck
Optimization of process settings to achieve highest wafer temperatures
and excellent temperature uniformity by
§ Back gas flow
§ ID / OD heating (Alpha factor)
100
Uniformity
Temperature
(Temperatur)
uniformity
458.0-460.0
456.0-458.0
80
Measurement Statistics
Uniform ity
2.44%
Mean
Range
Max
Min
430.76
10.50
434.70
424.20
454.0-456.0
60
452.0-454.0
450.0-452.0
40
448.0-450.0
446.0-448.0
0
y [mm]
20
-20
-40
[°C]
[°C]
[°C]
[°C]
444.0-446.0
442.0-444.0
440.0-442.0
438.0-440.0
8” Very Hot Chuck
436.0-438.0
434.0-436.0
-60
-80
x [mm]
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
100
80
60
40
20
0
-20
-40
-60
-80
-100
Chuck temperature: 600°C
Backside gas: 4 sccm
Wafer temperature: 430 °C
-100
432.0-434.0
430.0-432.0
428.0-430.0
426.0-428.0
424.0-426.0
422.0-424.0
420.0-422.0
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
Key hardware factors
RF target self bias voltage
1. RF power
0
B
RF
A
C
1 kW
Plasma
CS
USB
-100
-15 0
-200
-300
0
UB
UA
3 kW
-25 0
dB
dA
2 kW
-5 0
Target self bias voltage [V]
Target self bias voltage influenced by
§ Process pressure
§ RF power
§ Anode area
10
20
30
40
50
60
70
80
90
100
110
Ar flow [sccm]
2. Anode area
UPlasma
Cathode area ~ Anode area
Cathode area < Anode area
UB
UA
USB
USB = UA - UB
UB = UPlasma
UA / UB = (AreaB / AreaA)n
Target self bias voltage [V]
0
Higher anode area
-50
Lower anode area
-100
-150
-200
-250
-300
0
10
20
30
40
50
60
70
80
90
100
Ar flow [sccm]
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
110
Key hardware factors
Magnetron design
1.10
Normalized
Uniformity
thickness
PZT thickness and composition uniformity
influenced by
§ Erosion profile
§ Emission characteristic of sputtered
atoms
§ Scattering (~ pressure · distance)
§ Substrate temperature
Thickness uniformity of PZT films on Pt substrates
Thickness uniformity
1.15
1.05
1.00
0.95
Standard
§ Standard
setup
Improved
§ Improved setup
0.90
0.85
0
10
20
30
40
50
60
70
80
90
Radius [mm]
Composition uniformity
1.03
Composition (normalized)
Actual sputter performance
§ Deposition rate > 40 nm/min
§ Estimated target life time ~ 1600 µm
film thickness for 4mm target
1.02
1.01
ID
OD
620°C, ID
620°C, OD
1.00
0.99
0.98
0.97
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
Pb/(Zr+Ti)
1.000
1.004
Zr/(Zr+Ti)
1.000
0.989
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
100
In-situ PZT deposition process
General trends
Variation of substrate temperature
1.40
Relative Pb content can be influenced
§ Pb decrease with Ar flow increase
§ Pb increase with RF power increase
Composition (normalized)
§ Pb decrease with temperature increase
1.20
1.00
0.80
0.60
0.40
Pb/(Zr+Ti)
Zr/(Zr+Ti)
0.20
0.00
500° C
550° C
600° C
Variation of RF power
Variation of Ar flow
2.00
1.40
1.80
650° C
700° C
750° C
1.20
1.40
Pb/(Zr+Ti)
1.20
Zr/(Zr+Ti)
1.00
0.80
0.60
Composition (normalized)
Composition (normalized)
1.60
1.00
0.80
0.60
0.40
0.40
Pb/(Zr+Ti)
Zr/(Zr+Ti)
0.20
0.20
0.00
0.00
1.5 kW
2.0 kW
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
2.5 kW
50 sccm
100 sccm
250 sccm
350 sccm
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
In-situ PZT deposition process
6” PZT with PTO seed layer
§ Best PZT films achieved with a
PTO seed layer to promote the
nucleation of the PZT perovskite
structure
Performance of films deposited at 2 kW
§ For films sputtered at 1 kW
§ ε ~ 1500
§ tanδ = 3.2%
§ d33,f = 100pm/V
§ -e31,f = 7.5 C/m2
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
2
Polarisation [µC/cm ]
30
Intensity [a.u]
10
0
-10
-20
Ec (avg)
P rem (avg) = 23.5 µC/cm2
-40
P max (avg) = 42.5 µC/cm
-250
-200
-150
-100
-50
0
50
150
200
250
300
25 30 35 40 45 50 55 60 65 70 75 80 85 90
2 Theta
Polarisation vs. displacement
4.0
0.05
T h = 600°C
0.04
Th = 600°C
2.5
2.0
1.5
1.0
=> d33,f = 120 pm/V
0.5
=> d33,f = 120 pm/V
Polarisation [µC/cm2]
0.03
3.0
Displacement [nm]
100
2
Field [kV/cm]
Displacement vs. voltage
3.5
= 49.6 kV/cm
-30
-50
-300
38.25, PZT (111)
§ Similar performance for films
without TiO2 seed layer
20
85.71, Pt (222)
Th = 600°C
55.47, PZT (211)
40
40.02, Pt (111)
50
44.88, PZT (200)
§ Best piezoelectric data
§ ε ~ 1200
§ tanδ = 3%
§ d33,f = 120 pm/V
§ -e31,f = 12.6 C/m2
69.132, Si (400)
In-situ PZT deposition process
8” PZT with TiO2 seed layer
0.02
0.01
0.00
-0.01
-0.02
-0.04
-0.5
-0.05
-30
-25
-20
-15
-10
-5
0
5
Voltage [V]
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
10
15
20
25
30
-2000
2
= 12.6 C/m 2
=> -e31,f=>=e 12.6
C/m
-0.03
0.0
31,f
-1500
-1000
-500
0
500
1000
1500
2000
Displacement [nm]
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
In-situ PZT deposition process
Summary
§ The existing sputter equipment is capable to deposit PZT films in-situ with
the required perovskite structure
§ Therefore no additional annealing step is needed in the process sequence
§ Electrodes and PZT films can be deposited consecutively in a cluster tool
without breaking the vacuum
§ Piezoelectric performance of best films comparable to state-of-the-art films
deposited by chemical solution deposition (CSD)
§ Further improvements achievable by
§ Magnetron design
§ Target properties
§ Process optimization
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
=> Thickness and composition uniformity, deposition rate
=> Deposition rate
=> Piezoelectric properties
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]
The research leading to these results has received funding from
the European Community's Seventh Framework Programme
(FP7/2010-2013) under grant agreement n° 229196
Thank you for your attention
2nd International Workshop on Piezoelectric MEMS - Lausanne, 06./07.09.2011
M. Kratzer, Oerlikon Systems R&D, e-mail: [email protected]