Application of chemical-mechanical polishing for planarizing a high-K nano-composite polyimide insulator used in organic thin film transistors

To solve the large leakage current of heavily blended nanocomposite (PI and nano-TiO₂ particles) with high capacitance gate dielectric film, chemical-mechanical polishing (CMP) was used to planarize the interface between the PI-TiO₂ nano-composite film and pentacene. The hysteresis effect in organic thin film transistors (OTFTs) with the polished nano-composite dielectric surface was reduced because less charge was trapped in the interface. In OTFTs with high capacitance and a smooth surface, the threshold voltage improved from -22 to -5V, the sub-threshold voltage decreased from 3.44 to 0.50 (V/dec.), the current on/off ratio increased from 1.6×10⁶ to 3.53×10⁸, and the mobility increased from 0.416 to 0.624 (cm²V^-1s^-1).