Comparison of Different Sputter Processes for ITO: Planar DC versus Planar AC P. Sauer,H.-G.Lotz, A. Hellmich R. Kukla, J. Schröder Applied Films GmbH &,Co. KG, Alzenau, Germany
Outline n n n n n n Current ITO layers on glass and web Motivation for MF coating Influence of magnetic field Processing Equipment Results Conclusions
Current ITO layers on glass and web ITO on glass at higher substrate temperatures > 200 0 C Low specific resistivity < 200 micro * Ohm * cm Thickness of 20 Ohm layer : 100 nm. J ITO on web at low substrate temperatures < 100 0 C High specific resistivity ~ 500 micro * Ohm * cm Thickness of 20 Ohm layer : 250 nm. è high costs, poor optical properties (absorption, light scattering) L
Sheet Resistance of ITO layers for different Applications Fraunhofer Institute FeP, Dresden
Layer thickness for different specific Resistivities of ITO 700 600 ITO Layer Thickness [nm] 500 400 300 200 600 Mikro Ohm * cm 500 Mikro Ohm * cm 400 Mikro Ohm * cm 300 Mikro Ohm * cm 200 Mikro Ohm * cm 100 0 20 200 10 100 1000 Sheet Resistance [Ohm/Square]
ITO Transmission for different Layer Thickness Values 300 nm ITO 100 nm ITO
Motivation for Mid Frequency Sputtering of ITO Higher ion energy è Higher Surface Mobility? è Effect similar to higher Substrate Temp.? è Lower Specific Resistivity? Reduced arcing è Less nodule growth? è Longer target utilization without cleaning? è Lower Specific Resistivity?
Smart Web Sputter Coating Machine
Sputter Deposition of ITO in MF-Mode MF/AC Power Supply Matching Box Process Conditions: Gas Flow P(Cathode) 1-3 kw Ar flow rate 100-255 sccm Ar/O 2 flow rate 0-90 sccm Total Target Surface 1400 cm 2 Effective Power Density 0,7-2,1 W/cm 2 Rate (1,2,3 kw) 10, 20, 30 nm*m/min Cathode Substrate (PET)
Sputter Deposition of ITO in DC-Mode DC Power Supply left right Process Conditions: Gas Flow P(Cathode on left side) 1,368 kw P(Cathode on right side) 1,290 kw Ar flow rate 255 sccm Ar/O 2 flow rate 0-130 sccm Total Target Surface 700 cm 2 Effective Power Density Rate of Cathode on left side 1,95 W/cm 2 16 nm*m/min Cathodes Substrate (PET) Rate of Cathode on right side 16,6 nm*m/min
Specific Resistivity for different power levels in MF-Mode on Glass 3500.0 Specific Resistivity [Mikro Ohm * cm] 3000.0 2500.0 2000.0 1500.0 1000.0 500.0 P = 1 kw P = 2 kw P = 3 kw 0.0 0 10 20 30 40 50 60 70 80 90 Ar/O2-Flow [sccm/min]
Specific Resistivity on Glass and PET (MF-Mode, 2 kw) 3500.0 Specific Resistivity [Mikro Ohm * cm] 3000.0 2500.0 2000.0 1500.0 1000.0 500.0 PET Glass Glas Folie 0.0 0 10 20 30 40 50 60 70 80 90 Ar/O2 - Flow [sccm/min]
Specific Resistivity on PET (MF-Mode, 2 kw) for different layer thickness values 750 Specific Resistivity [Mikro Ohm * cm] 700 650 600 550 500 450 400 0 20 40 60 80 100 120 140 160 180 200 ITO Layer Thickness [nm]
Specific Resistivity and Roughness of MF sputtered ITO layers on PET (ITO Thickness 80-181 nm, 1.0 kw) Specific Resistivity [MicroOhm * cm] 800 700 600 500 400 300 200 100 20 18 16 14 12 10 8 6 4 2 Roughness Rmax [nm] 0 0 60 80 100 120 140 160 180 200 ITO Layer Thickness [nm]
Specific Resistivity and Absorption of MF sputtered ITO layers on PET (Thickness 40 nm, 1.0 kw, A=1-R-T) 1400,0 16 1200,0 14 Specif. Resistivity [mikro Ohm*cm] 1000,0 800,0 600,0 400,0 200,0 Specific Resistivity Absorption (incl. PET) 12 10 8 6 4 2 Absorption (400 nm) in % 0,0 0 0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 Ar/O2 Flow [sccm/min]
Specific Resistivity and Absorption of DC sputtered ITO layers (Thickness 43-48 nm, 1,37 kw, A=1-R-T) 1400,0 16 spec. Resistivity (MikroOhm*cm) 1200,0 1000,0 800,0 600,0 400,0 200,0 Specific Resistivity Absorption (incl. PET) 14 12 10 8 6 4 2 Absorption (400 nm) [%] 0,0 0 20 40 60 80 100 120 140 Ar/O 2 -Flow [sccm/min] 0
Specific Resistivity of MF-sputtered ITO layers on Glass and PET substrates (P=1.3 kw). Rate of first Cathode: 16 nm * m / min; Rate of second Cathode = 16,6 nm * m / min 3500.0 spec. Resistivity (MikroOhm*cm) 3000.0 2500.0 2000.0 1500.0 1000.0 500.0 0.0 Left cathode 22 sccm/min Right cathode Glass LS, Rate PET LS Glass RS PET RS 0 20 40 60 80 100 120 140 Ar/O2-Flow [sccm/min]
Influence of magnetic field on Target utilization and Specific Resistance ka Magnetic field strength 30 20 10 0-10 N/S/N magnetic field HLK optimised mag. field ToraMag 0 50 100 150 200 250-20 -30 Targetwidth / mm
Erosion profiles using different magnetic fields Targetthickness / mm 9 8 7 6 5 4 3 2 1 0 0 20 40 60 80 100 Targetwidth / mm Cathode utilization HLK 22 % ToraMag 40 %
Specific Resistivity on PET for different magnetic field strength Spec. Resistance 750 700 650 600 550 500 450 ITO Specific Resistance HLK ToraMag 400 0 50 100 150 200 ITO Layerthickness
Conclusions : Similar layer properties were obtained with MF and DC sputtering. Operating point for sputter process must be optimized for both cathodes separately. No beneficial effect of MF sputtering compared to DC. Higher Target utilization using adapted mag. Fields for planar cathodes. Save Money :Use optimized mag. fields Don t change from DC to MF sputtering of ITO
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