Study on Preparation of High-kOrganic–Inorganic Thin Film for Organic–Inorganic Thin Film Transistor Gate Dielectric Application

A simple solution-based deposition technique combined with spin-coating is a plausible way to prepare ultra-thin organic–inorganic nanocomposite films. In this study, we describe the spin-coating deposition of a colloidal nanoparticle suspension to obtain an ultra-thin organic–inorganic composite film as a gate insulator for organic thin film transistor (O-TFT) application. To obtain a homogenous organic–inorganic composite film, well-dispersed TiO2 nanoparticles in γ-butyrolactone and polyimide are important; therefore, several dispersants were assessed on the basis of the measurement of the rheological behavior of slurries. The thickness of the organic–inorganic composite film is mainly determined by the speed of spin-coating and viscosity of slurries. An approximately 4000-Å-thick nanocomposite film with homogeneous distribution of TiO2 nanoparticles in polyimide and low roughness was obtained after curing at 200 °C, resulting in a low leakage current density of the nano-composite film, when less than 2 vol % TiO2 nanoparticles were well dispersed in polyimide slurry. The dielectric constant of the organic–inorganic nanocomposite increases with increasing TiO2 content in polyimide, being situated in the range between 4 and 5.