Ladder-type silsesquioxane copolymer gate dielectrics for gating solution-processed IGZO field-effect transistors

Field-effect transistors (FETs) based on solution-processed indium-gallium-zinc oxide (IGZO) exhibited excellent electrical properties, including a high carrier mobility over 1 cm²/V s and an on/off current ratio over 10⁷. Solution-processable gate dielectric materials with excellent electrical strength were required instead of inorganic oxide gate dielectrics such as SiO₂, Al₂O₃, and HfO₂. In this manuscript, we demonstrated the use of a ladder-type poly(phenyl-co-methacryl silsesquioxane) (PPMSQ) copolymer as a gate dielectric in IGZO FETs. Methacryloxypropyl groups in the copolymer were introduced to crosslink the polymer chains via thermal annealing. Thermal annealing at 200 °C enhanced the electrical strength of the gate dielectric layer because of the formation of a network structure with a reduced free volume. The resulting IGZO FETs based on 200 °C-annealed ladder-type PPMSQ gate dielectrics exhibited an electron mobility of 1.2 (±0.05) cm²/V s, a threshold voltage of 17 (±2) V, and an on/off current ratio of 1.5 (±0.7) × 10⁸. The use of the polymeric ladder-type PPMSQ gate dielectrics for gating the IGZO FETs provided a novel approach to realizing future flexible electronics.