The 11 th US-Korea Nanosymposium Choi, Jun-Hyuk 2014. 09. 29 Korea Institute of Machinery & Materials
About KIMM Nano-research Bldg Clean RM Five Research Divisions; 1. Advanced Manufacturing Sys. 2. Extreme Mechanical Eng. 3. Nano-Convergence Mechanical Systems 4. Environmental and Energy Sys. 5. Mechanical Systems Safety 2
Facilities/Infra. For Nanoimprint at wafer scale For Nanoimprint in Large area Master/Molds Large area Mold fabrication Etched master at 8 wafer 3/26
Metal patterning infrastructures Film Quality w.r.t. dep. rate Ag deposited By E-beam v.s. 5.0 A /S 0.5A /S Siliver Milling Test w.r.t. the variables of current, time, and tilting angle Target Sub. Tilting angle ~60 A Tilting angle ~0 Current 300 A Time 1min B 4/26
Outlines 1 Laboratory Introduction Members / Facility Researches for Nanoimprint 2 Fabrication strategies Introduction of various in-house self technologies Metal Imprint Transfer 3 Application to Optoelectronic Devices Photoluminescence Transparent electrode in Hybrid Cell Photovoltatics 4 Closing remarks
Lift-off for well-round shaped Metal dots Process Scheme GT-IJPEN 2014 7/26
Metal direct etch, Nanoimprint CMOS imaging chip + Plasmonic nano filter array + nanoimprint process Front Illumination &Reflection White Light Source SiO2 Al filter Si-wafer 8/26
Embedded Ag nanopatterning 1. Bilayer Hybrid NIL -> Lift-off 2. Metal Imprint Transfer Point of the embedded configuration on multilayer optoelectronics Non-uniform current flow (Leakage current) Reduced efficiency Electric field/electron injection enhancement Electron transport effects Thermal decay, reduced life-time Charge recommbination in solar cells Thermal decay, reduced efficiency 9/26
1. Bilayer Hybrid NIL and following Lift-off Process Scheme (a) (b) (b) Thermal Resist UV Resist Step (c) (c) (d) Step (d) (e) J. Nanophotonics 2014 Patent 1304467 Step (e) (a) Half pre-cure of the coated UV resist (c) Thermal Imprint, UV exposure while pressed -> Complete cure of UV resist (d) Ag deposition by E-beam evaporation (e) Lift-off of thermal resist on top layer 10/26
200nm Ag array (embedded) 150nm Ag array (embedded) 265nm Ag array (embedded) 235nm Ag array (embedded) 11/26
2. Metal Imprint Transfer (a) Process Scheme Ag E-beam Evaporation (c) (d) Mold release UV Exposure (b) UV curable resist Spin-coated Half pre-cured Qz substrate (a) E-beam evaporation of Ag on mold pattern (b) Half pre-cure of UV curable resist (c) Only Ag on the top surface of mold in contact with half-cured resist, and UV exposure (d) Mold release Kor. Patent: 2013-0044343, 2014-0037491 US Patent: 14/194084 Small 2014, Published Note: Embedded Dot Arrays 1) Half pre-cured UV-NIL resist 2) Limitedly Imprinted Depth via Pressure Control 3) Minimized Leakage Current at device depo. 12/26
Completely embedded Planar embedded Half embedded 13/26
Metal Meshes in Hybrid Cell Process Scheme for Si-PEDOT Hybrid Photovoltaic cell 15/26
<Metal-based Meshes fabricated by Metal Imprint Transfer > T peak of 91.6% @ 24 Ω/sq T peak of 90.9% @ 16 Ω/sq T peak of 89% @ 28 Ω/sq 16/26
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Current density (ma/cm 2 ) Voc (V), Jsc (ma/cm 2 ) 40 35 30 25 20 15 10 Au mesh (2 x 100 um) Au mesh (2 x 200 um) 5 Au mesh (2 x 300 um) 0 ITO 0.0 0.1 0.2 0.3 0.4 0.5 0.6 40 35 30 25 0.6 0.4 0.2 0.0 Voltage (V) 2x100 2x200 2x300 ITO Au mesh size (um) Low shunt resistance 70 60 50 40 10 5 0 PCE (%), FF (%) EQE (%) 100 80 60 40 20 0 Au mesh (2x100 um) Au mesh (2x200 um) Au mesh (2x300 um) ITO 400 600 800 1000 Sample Wavelength (nm) V oc (mv) J sc (ma/cm 2 ) FF (%) PCE (%) ITO 491.5 27.3 44.35 5.95 Au mesh (2x300 um) 532.5 33.17 60.7 10.73 Au mesh (2x200 um) 539.2 36.03 67.8 13.17 Au mesh (2x100 um) 548.7 31.08 68.1 11.6 18/26
Tunable Plasmonic Nanostructures Metal Imprint Transfer Annealing at > 150 C Confirmed Tunable plasmonic Properties Plasmonic peak shifts as annealing temperature increases. Green PL Intensity increased more than 400%, w.r.t. Ref. 19/26
Spectral Transmittance- Measured & Simulated 100 Anneal Temp. dependence at 200nm 80 Transmittance (%) 60 40 20 B-40-1 B-40-2 B-40-3 B-40-4 250 C 200 C 150 C R.T 0 300 400 500 600 700 800 900 1000 100 80 A-40-4 B-40-4 C-40-4 Wavelength (nm) Transmittance (%) 60 40 20 150nm 200nm 0 300 400 500 600 700 800 900 1000 Wavelength (nm) 265nm At 40nm, 250 (a) cylinder shape 에서 ellipsoidal 로변하는과정의 transmittance (b)~(d) Electric field intensity of cylinder shape & ellipsoidal shape with a,b=80nm 20/26
Photoluminescence Improvements <Annealing Temp.-dependence> incident light PL peak intensity Mold pattern size: 150nm Ag Thick: 40nm Anneal temp.: R.T./150/200/250 C Ref.glass Ref.NOA A-40-1 A-40-2 A-40-3 A-40-4 Double-grating excitation monochromator Incident light 5 5 glass Sample compartment 320 mm spectrograph with double-grating turret A/B/C ; 150/200/265-nm in mold pattern dia. 20/40/60; 20/40/60-nm in Ag thickness 1/2/3/4; RT/150/200/250 C for annealing temp. 350 400 450 500 550 600 650 700 Wavelength(nm) PL enhancement rate Sample w.r.t Ref. glass w.r.t. Ref-NOA A-40-1 280% 317% A-40-2 268% 303% A-40-3 259% 293% A-40-4 465% 518% 21/26
<Ag Thick.-dependence> <Mold pattern size.-dependence> PL peak intensity Mold pattern size: 150nm Anneal temp.: 250 C Ag Thick: 20/40/60-nm Ref.glass Ref.NOA A-20-4 A-40-4 A-60-4 PL peak intensity Mold pattern size: 150/200/265-nm Anneal temp.: 250 C Ag Thick: 40-nm Ref.glass Ref.NOA A-40-4 B-40-4 C-40-4 350 400 450 500 550 600 650 700 Wavelength(nm) PL enhancement rate Sample w.r.t Ref. glass w.r.t. Ref-NOA A-20-4 243% 276% A-40-4 465% 518% A-60-4 399% 446% 350 400 450 500 550 600 650 700 Wavelength(nm) PL enhancement rate Sample w.r.t Ref. glass w.r.t. Ref-NOA A-40-4 465% 518% B-40-4 371% 415% C-40-4 174% 200% 22/26
Closing Remarks Research Infrastructures for Nanostructures/Patterning Nanoimprint-based nanopatterning and its application in Optoelectronics Several approaches for metallic nanopattern fabrications in plasmonic fields Global Collaborations UC Berkeley-Micromechanical Analysis and Design (BMAD) IMRE, Singapore AMO GmbH Aachen Industrial Collaborations APN Hutem Co. nanolambda Korea Company Samsung Electronics-Manufacturing Institute Youngchang Chemical Co. Ltd 23/26
Members Nanoimprint - Process, Tools, Functional mater. - Appl.: R-RAM, Sensors, (O)LED 3D Multiscale Architecturing - Nanowire structuring - Nanomaterials self-assembly Plasmonic sensors, Light emitting - Metal nanostructuring - Metal NP. Self-growth Staffs Lee, Eung-sug: Ultrafind fabrication, Nanomechatronics Jeong, Jun-ho: Nanolithography, Nanoimprint Choi, Jun-hyuk: Metal nanopattering, Direct/Roll Imprint Choi, Dae-geun: Nanoimprint mater. Process chemistry Lee, Ji-hye: Nanowire, mask fabrication, biosensors Jeong, Joo-yeon: Electronics, Plasmonic optics 24/26
Thank you for your attentions
Research area <Nanopatterning, Lithography> <Metal nanopattern array> <Optoelectronic Applications> <Etching> <Optics-based Sensors> <Metal pattern, Lift-off> <Plasmonic Lithography> 26
Research directions Multilayer, Enlarged Solar cells Planarized Struc. Plasmonic Litho. Mask Plasmonic sensors Undercut 3D Struc. Optoelectronics Embedded structure profile Infrastructure of metallic nanopatterning