JOANNEUM RESEARCH Forschungsgesellschaft Institute MATERIALS, Weiz, Austria Large-area patterning by roller-based nanoimprint lithography Ursula Palfinger, Dieter Nees, Stephan Ruttloff, Markus Leitgeb, Maria Belegratis, Barbara Stadlober www.joanneum.at
Outline 2 Outline Motivation Small structures on large areas Technology Roll-to-roll Nanoimprinting (R2R NIL) Processes Machinery Materials Prerequisites for residual-free imprinting Applications Roller-based fabrication of highly resolved metal patterns by a combination of residual-free NIL and a subsequent lift-off for transparent conductive foils and product ID features Summary
Motivation 3 Small structures on large areas Superhydrophobicity Lotus effect Light management Architecture Antireflectivity Low friction Riblets Point-of-Care Diagnostics Structural Colours Camouflage, Attraction Where is highly resolved patterning on large areas interesting? Others: Transport Traffic Security Packaging Energy Harvesting Flexible electronics OFETs Adhesion Gecko-effect
Motivation 4 Small structures on large areas Superhydrophobicity Lotus effect Light management Architecture Antireflectivity Low friction Riblets Point-of-Care Diagnostics Structural Colours Camouflage, Attraction How can we produce them? 1) micro and nano 2) 2D 2.5D 3) large flexible areas 4) industrial process Flexible electronics OFETs Adhesion Gecko-effect
Technology 5 1 2 Working stamp Substrate, resist Nanoimprint lithography Fast + accurate method for structure transfer UV or thermal curing of resist Very versatile (geometries, structure size) 3 Contact, imprint 4 Curing: T, UV Release
Technology 6 Nanoimprint lithography Fast + accurate method for structure transfer UV or thermal curing of resist Very versatile (geometries, structure size) Stamp Imprint CD = 1.6 µm
Technology 7 Nanoimprint lithography Fast + accurate method for structure transfer UV or thermal curing of resist Very versatile (geometries, structure size) Stamp Imprint CD = 200 nm
Technology 8 Nanoimprint lithography Working stamp Substrate, resist Contact, imprint Curing: T, UV Critical issues Batch NIL (serial) - Master (pattern quality, roughness) - Control of adhesion between master and resist - Resist viscosity (filling) - Curing behavior (fast, low shrinkage) - Fabrication volumes and process time - Upscaling? Release
Technology 9 Roll-to-Roll Nanoimprint lithography Working stamp Substrate, resist Photoresin (structured and cured) Contact, imprint Curing: T, UV Photoresin (liquid) Shim on roller Release Substrate line pressure rubber-coated counter roller
Technology 10 Roll-to-Roll Nanoimprint lithography Max. web width = 250 mm Web speed = 0.5 30 m/min Max. UV intensity = 200 W/cm Line pressure UV-NIL = 18 kn Line pressure HE = 100 kn
Low (<0,01) Throughput (m 2 /s) Medium (0,01-1) High (>1) Technology 11 Resolution and throughput of printing technologies 100 Gravure Offset Flexo Rotary screen 1 R2R Nanoimprint lithography Flat screen 10-2 R2R photolitho Inkjet R2R-vacuum 10-4 Laser ablation High Resolution (< 10 µm) Medium Resolution (10-50 µm) Low Resolution (> 50 µm) 1 10 100 500 Minimum feature size (µm) Source: OE-A 2009, 3D-MM
Low (<0,01) Throughput (m 2 /s) Medium (0,01-1) High (>1) Technology 12 Resolution and throughput of printing technologies 100 Gravure Offset Flexo Rotary screen 1 R2R Nanoimprint lithography Flat screen 10-2 R2R photolitho Inkjet R2R-vacuum 10-4 Laser ablation High Resolution (< 10 µm) Medium Resolution (10-50 µm) Low Resolution (> 50 µm) 1 10 100 500 Minimum feature size (µm) Source: OE-A 2009, 3D-MM
Application 13 Creation of highly resolved metal patterns in R2R environment metal residue-free imprint stuctured metal layer
Applications 14 Critical for residual-free imprint: PATTERN GEOMETRY Structure depth and resist thickness l : line width s : space width d : structure depth h o : initial resist film thickness for open patterns
Applications 15 Critical for residual-free imprint: RESIST FLOW BEHAVIOR Squeeze flow model Stefan s equation : p t : imprint time η : resist viscosity l : imprinted line width p : imprint pressure h r : residual resist film thickness h o : initial resist layer thickness For vanishing residual resist film thickness the imprint time approaches infinity... H. Schift, J. Vac. Sci. Technol. 2008
Applications 16 Critical for residual-free imprint: SURFACES VS. RESIST CHEMISTRY Spontaneous dewetting and balance of interfacial forces S = g Substrate/Shim (g Substrate/Resin + g ResinShim ) < 0 g X/Y : interfacial energy S: spreading coefficient SJ Choi, J. Colloid. Interface Sci. 2009
Applications 17 Critical for residual-free imprint: CHOICE OF RESIST UV-NIL resist for aqueous lift-off Monomer low viscosity water soluble monofunctional Acrylate Photoinitator e.g. Non-ionic surfactant e.g. η = 10 mpas polar rest group Tuning of interfacial energies 20 mn/m < g < 45 mn/m Auner, Palfinger et al, Organic Electronics, 2009+2010
Applications 18 Residual-free R2R imprint SEM: top view SEM: cross section Zoom UV-Resist PET
Applications 19 Residual-free R2R imprint SEM: top view SEM: cross section Zoom 1 metallization UV resist 2 water lift-off PET
Applications 20 Al lines, CD = 1.6 µm 3 nm Cr + 30 nm Al Lift-off with H 2 O
Applications 21 Al patterns, CD = 1.6 µm 21 web direction
Applications 22 Al patterns, CD = 400 nm l/s = 1:4 web direction
Applications 23 Application nano : Metal grids for transparent conductive foils SEM 400 nm
Applications 24 Application nano : Metal grids for transparent conductive foils SEM 400 nm Source: PolyIC Source: Samsung PyzoFlex technology Flexible displays, touch panels, sensor surfaces, shielding foils,
Applications 25 Application nano : Metal grids for transparent conductive foils SEM 200 nm
Summary 26 Summary Roller-based nanoimprinting is a large area, high resolution patterning process with very high potential. Residue-layer free R2R UV-NIL is possible, when pattern geometries and stamp and resin surface chemistry is optimized. We developed an acrylate-based imprint resin for water-based lift-off and used it for highly-resolved metal patterning on foil without the need of etching. Applications can be seen in electronics, optics, sensing, security features, shown examples: transparent conducting, packaging
Acknowledgements Dieter Nees Markus Leitgeb Herbert Gold Stephan Ruttloff Laco Kuna Volker Schmidt Maria Belegratis Barbara Stadlober
Lift-off in progress Thank you for your interest!