Organic gate insulator materials for amorphous metal oxide TFTs

Numerous solution-processed dielectrics were studied in metal oxide thin film transistors (TFTs) to understand their potential application in flexible display technology. A series of dielectrics was synthesized and systematically formulated to deposit organic gate insulating thin film layers that demonstrate low leakage current (≤10^-8 A/cm2 at 2 MV/cm), high breakdown voltages (>150 V), film flexibility, photopatternability (5-10 μm via hole size), increased temperature stability (up to temperatures of 300 °C), and resistance to common chemicals used in the indium gallium zinc oxide (IGZO) TFT fabrication process. In particular, surface modification improved the stability of bottom-gate organic gate insulators during the sputtering, patterning, and annealing processes for the IGZO active layer on the dielectric surface. The best IGZO TFT performance was achieved when certain Polyera organic gate insulators were incorporated in top-gate top-contact IGZO TFT devices, yielding excellent mobility (~15 cm²/V·s), V_th ~ 0 V, negligible hysteresis, sharp sub-threshold swing (~300 mV/dec), and good bias temperature stress stability. When combined with polymer substrates such organic gate insulators yield truly flexible IGZO TFTs compatible with large-scale production methods.