Chemical Vapour Deposition at Atomospher

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Presented at MRS Spring Meeting 2011. \"A key issue for the production of thin films in photovoltaics, optical coatings, or corrosion protection is cost reduction. In this context, vacuum based processes are often limited especially when large substrates are to be processed. Atmospheric pressure (AP) processes instead allow to process large substrates with mobile coater head technology where the substrate is fixed, but are also ideally suite ... Shared on http://www.vacuumcoating.info

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Slide 1:

Chemical Vapour Deposition at Atmospheric Pressure H. Althues, G. Mäder, V. Hopfe, E. Beyer, and S. Kaskel Prof. Dr. Stefan Kaskel Fraunhofer Institute Materials and Beam Technology (IWS) CVD and Thin Film Department Winterbergstraße 28, 01277 Dresden, Germany © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Organization  Motivation  AP CVD Technology at IWS  DC Arc Plasma  Thermal CVD Technology  Applications and performance  Etching  Deposition  AR Coating  TCOs  Carbon Nanotubes  Summary © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

Slide 3:

Silicon Wafer Processing Saw damage etching Texture Phosphor doping Contacting Passivation/ AR-Coating Edge- isolation Antireflex- coat Phosphor- etching Front contact • „Technology-Mix“: wet chemical, Vacuum, CVD, Oven, Screen print, … • High number of handling steps causes • Enhanced production costs • Wafer damage (d <200 μ m) © Fraunhofer IWS Kürzel: Datum und Name der Präsentation p-Si-Wafer Back contact n-Si p-n-junction

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PECVD-Technology for large substrates  Flying coater head  Inert atmosphere  300 x 300 mm ² ,  600 x 1 500 mm ² (2 x 3 Sources) © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Plasma source development - DC arc 150 mm 250 mm • scalable linear plasma sourcethermal plasma • plasma gases: N 2 /O 2 /NH 3 /H 2 …+ Ar • use of remote plasma • plasma parameters for 250 mm LARGE: - 50 - 100 A - 15 - 30 kW - plasma gas flow: 40 to 110 slm 350 mm © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Dry Etching Technology (NF 3 , F 2 ) Saw damage Texturing Edge Isolation p-Si shunt n-Si Inverse pyramids Industrial reference is 100% Porous © Fraunhofer IWS Kürzel: Datum und Name der Präsentation 1.75 % rel. Eff. Incr.

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Thermal APCVD for metal oxide deposition  Features  continuous inline-process  deposition in defined atmosphere (gas lock system)  flexible process parameters (temperature, gas composition, flow)  reaction of precursor and reactive gas near to the surface © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Doping Films  Homogeneous B-Si-O Films  Thermal or Plasma CVD Possible  Homogeneity better than 3 %  Etchable  Selective Emitter or Complex Structures 115 110 105 Transmission Mikro-ATR, Ge-Kristall korrigiertes ATR-Spektrum Ch.Density N v (cm -3 ) d BSG = 390 nm 100 95 90 85 80 75 70 65 60 4000 3500  B-O-H  B-H  B-O  /  B-O Si-O  Si-O B 2 O 3 + SiO 2 (PECVD)  B-O B 2 O 3 + SiO 2 (therm. CVD) 3000 2500 2000 -1 1500 1000 Wellenzahl  [cm ] Distance from Surface © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Silicon Nitride AR Coating • Specification: • RI 2.1 (550 nm) • Thickness 70 nm • H-Content >10 at.% • Homogeneity better than ±3% Process parameters: • Plasma gas: Ar + N 2 + NH 3 • Remote gas: NH 3 • Precursor: SiH 4 , TMS Si(CH 3 ) 4 • Substrate: Si (100) and poly crystalline • Substrate temperature: 150-400°C © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Titanium dioxide thin films  Properties  High film quality at low temperatures (250 °C)  Homogeneous and dense films (refractive index = 2,4)  High crystallinity (anatase TiO 2 ) Concentration ( umol /l) 12 10 #28 #13 #12 8 #14 6 4 2 #25 0 0 20 40 60 80 100 120 140 160 180 #2 #23 #27 #22 #20 #4 #8 Methylene blue decomposition AP-CVD #26 d = 25 nm d = 65 nm TiO 2 -coatings on steel plates time (h) © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Transparent, conductive SnO 2 :F thin films Properties  Rate:10- 50 nm*m/min Total transmittance T I / % 100  High Transmission (> 85 %)  Spec. resistance: 1,3*10 -3  *cm  Homogeneous (R I = 1.95) 80 total transmission 60 FTO-Coating on Corning 1737 Reference (Asahi U type) 40 20 diffuse transmission 0 300 400 500 600 700 800 Wave length l / nm © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Fluorine-doped tin dioxide (FTO)  Structured deposition of transparent, conducting layers  crystalline  Adjustable texture SnO 2 -Lines Ra = 40 nm AFM y x 20 mm © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Vertical oriented carbon nanotube films Process steps  Dip coating of catalyst precursors VA CNT heights [um]  CVD process: C 2 H 4 as carbon precursor substrate: wet-chemical metal foil dip coating catalyst layer 200 150 100 40 min 50 50 μ m CVD process MWCNT forest 0 0 10 20 30 growth time [min] 40 © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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Direct laser patterning of vertical aligned CNT films  laser: Nd:YAG, 355 nm, 10 ns, 150 J/cm²  structural depth and film morphology depends on number of pulses and laser power 1 pulse 5 pulses 20 pulses 5 μ m 5 μ m 5 μ m © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

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CNT based Electrodes: Supercapacitor  Electrolyte double layer capacitor Reference AC Carbon - - - - - - - - - - - - ----- ----- ----- ----- ----- +++++ + +++++ + +++++ + + +++++ + +++++ + substrate with VA-CNTs CNT Forest - electrolyte V + membrane © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

Slide 16:

Summary  AP CVD Technology at IWS  DC Arc Plasma  Thermal CVD Technology  Applications and performance  Etching  Deposition  AR Coating  TCOs  Carbon Nanotubes © Fraunhofer IWS Kürzel: Datum und Name der Präsentation

Slide 17:

Acknowledgement Supported by EU: N2P BMBF: PLASMACELL Team at IWS T. Abendroth S. Dörfler L. Kotte G. Mäder J. Roch S. Tschöcke Contact: Stefan.Kaskel@iws.fraunhofer.de Thomas Schülke Fraunhofer Center USA © Fraunhofer IWS Kürzel: Datum und Name der Präsentation