Improvement of device performance of Ph-BTBT-10 field-effect transistors fabricated on a HfO ₂ /alicyclic polyimide double-layered gate insulator

We report on the FET properties of 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) on a HfO 2 /alicyclic polyimide double-layered gate insulator at an elevated temperature. The patterning of semiconductor and polymeric insulator layers is also discussed using the surface selective deposition of solution onto the wettable region (self-assembled monolayer-coated oxide layer) and unwettable region (bare metal oxide layer) obtained by vacuum ultraviolet light (172 nm) irradiation. A multilayered film of 20–30 nm thick Ph-BTBT-10 and a double-layered gate insulator consisting of 30–40 nm thick alicyclic polyimide on high- k metal oxide films leads to a reduction in the operating voltage and the interfacial trap density at the gate insulator interface. The mobility of the FETs was improved from 0.4 to 2.4 cm 2 V −1 s −1 by thermal annealing of Ph-BTBT-10 at 120 °C due to the transition from a monolayer to a bilayer structure and the use of alicyclic polyimide as the polymer gate insulator.