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Low-temperature processing of oxide thin-film transistor via combustion processing

Low-temperature processing of oxide thin-film transistor via combustion processing. Combustion processing. Self-propagating High-temperature Synthesis ( SHS) Reagents react itself and produce heat (exothermic reaction) Process stages Ignition Front propagation Product cooling.

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Low-temperature processing of oxide thin-film transistor via combustion processing

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  1. Low-temperature processing of oxide thin-film transistor via combustion processing

  2. Combustion processing Self-propagating High-temperature Synthesis (SHS) Reagents react itself and produce heat (exothermic reaction) Process stages Ignition Front propagation Product cooling Typically powder ~10μm Metal + (Boron, Carbon, Nitrogen)

  3. Combustion processing Reaction subzones Ignition! Cooling down subzone Afterburning subzone Heat transfer Structure formation Main heat release subzone Intense heat transfer Preflame subzone

  4. Combustion processing Primary parameter is Tm(Maximum combustion temperature) Increasing Tm – Inert diluent Decreasing Tm – Preliminary warming-up Adiabatic combustion temperature Complex flamewave propagation equation is not required for thin-film situation

  5. Combustion processing Classical SHS processes Metal + Boron Metal + Carbon Metal + Nitrogen Metal + Silicon Metal + Hydrogen Metal + Metal Metal + Sulfur, Selenium Generally oxidation of metal or intermetallic formation

  6. Combustion processing Metal nitrates-Organic ligand reaction Sulfur-containing ligand produces metal sulfides Thiosemicarbazide(TSC) ligand Thiourea(Thio) ligand Reagents [Ni(TSC)2](NO3)2 [Co(TSC)3](NO3)3·3H2O Fe(TSC)2(NO3)2·2H2O Cu(TSC)2(NO3)2 [Zn(TSC)2](NO3)2 Zn(Thio)2](NO3)2 Cd(Thio)2(NO3)2 Pb(Thio)2(NO3)2 Bi(Thoi)3(NO3)3 In(Thio)3(NO3)3

  7. ThermochimicaActaVolume 6, Issue 4, June 1973, Pages 353-360 Combustion processing Metal nitrates-Organic ligand reaction Similar with explosive reaction of urea nitrate (Highly exothermic reaction) 3[ ] + → + 6H2O + 3N2O + CO2 Urea Fuel Nitrate Oxygen provider Urea nitrate: rocket fuel Cyanourea

  8. Combustion processing Combustion process with sol-gel precursor Starting material + Copper(II) nitrate Acetylacetone + Ammonia water → Precipitations dissolved in nitric acid As a result: Existing ions: Cu2+, NO3-, Acetylacetonate, NH4+, H+

  9. Combustion processing FTIR spectra Precursor have various ligands Metal nitrate Metal-ammine complexes Metal diketano complexes UV-vis Absorption spectrum

  10. Combustion processing Involved reaction Chloride + Ammonia + Nitric acid No combustion: Nitrate oxidant is required for reaction DTA TGA DTA TGA Nitrate only No exothermic reaction observed Nitrate + Ammonia + Nitric acid Combustion of ammonia (270ºC) High power High ignition temperature

  11. Combustion processing Involved reaction Oxidation of carbon residual No carbon residual Nitrate + Acetylacetone Combustion of acetylacetonate ligand (147ºC: lower temperature) Low power Low ignition temperature Nitrate + Acetylacetone + Ammonia + Nitric acid Lower temperature: 131ºC Acetylacetone ignition → Acetylacetone combustion → Ammonia ignition → Ammonia combustion

  12. Combustion processing Reaction mechanism Ignition temperature varies by metal in precursor Direct ignition of precursor complex - O Ignition of free organic molecules - X acetylacetone is not strictly needed Diethylenetriamine Trioctylphosphine Hexanethiol

  13. Combustion processing Application of thin-film transistor Combustion process Low temperature ~200ºC (For ignition) Conventional sol-gel reactions are endothermic Process >400ºC

  14. Combustion processing Precursors and reactions 1) Urea combustion In(NO3)3·2.85H2O, Zn(NO3)2·6H2O,SnCl2(Tin nitrates are unstable) with NH4NO3, Urea 2) Acetylacetone combustion In(NO3)3·2.85H2O, Zn(NO3)2·6H2O,SnCl2 with NH4NO3, Acetylacetone, Ammonia NH4NO3 (Ammonium nitrate): Provides NO3- ions which SnCl2 cannot

  15. Combustion processing DTA results: reaction completes at low temperature ~200ºC Crystallization temperature: Lower Tc from combustion process? Exceptional behavior of ZTO: Combustion energy may not be sufficient to complete reaction

  16. Combustion processing XPS, TOF-SIMS results Combustion Conventional Low carbon M-O-M bonding established at lower temperature

  17. Combustion processing Device performance In2O3: Lowest processing temperature

  18. Combustion processing 200ºC processed flexible device Arylite substrate a-Al2O3 (spin-coating) μsat = 6.0cm2V-1s-1 Ion/Ioff = 103

  19. Conclusions • Exothermic reaction of metal nitrate with urea, ammonia and acetylacetone • - Achieves high local temperature • - High quality metal oxide formation with low substrate heating temperature • Low-temperature process for TFT fabrication • - Combined with low-temperature synthesized gate dielectric • - Enables flexible device on polymer substrates • Some mechanisms are not elucidated yet • - Oxygen is from air or oxygen from precursors

  20. Future work • GI-active layer chain reaction process Ammonia-containing low-temperature precursor (Zinc oxide dissolved in Ammonia) High ignition temperature Acetylacetone-based low ignition temperature precursor (Gate dielectric) Low ignition temperature

  21. Experiment (ZTO) 0.025M Sn(OtBu)4 0.033M Sn(OtBu)4 0.037M Sn(OtBu)4 0.04M Sn(OtBu)4

  22. Experiment (ZTO) ZnOAc,300°C (Zn+Sn)OAc,300°C ZnOAc,350°C

  23. Experiment (ZTO) Mixed 1 layer (Alkoxide+Acetate) – Poor characteristics

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