Fabrication and Characterization of Flexible Thin Film Transistors on Thin Solution-Cast Substrates

We report flexible ZnO thin film transistors (TFTs) fabricated on 5 mu m thick solution-cast polyimide substrate. Plasma enhanced atomic layer deposition (PEALD) was used to deposit Al2O3 dielectric and ZnO active layers respectively. The highest processing temperature was 200 degrees C. The flexible ZnO TFTs we fabricated have very similar characteristics to devices fabricated on glass substrates. Typical TFT mobility was greater than 12 cm(2)/V center dot s for a gate electric field of 2 MV/cm. Simple mechanical releasing can be used to detach the polyimide substrate from the rigid carrier. Device performance showed almost no degradation after releasing. Repeated bending test using homemade roller-flex testing apparatus was conducted. The flexible ZnO TFTs were repeatedly bent and flattened to a minimum radius of 1.6 mm for more than 10,000 cycles with little change in device characteristics. These results demonstrated solution-cast thin polymeric film as a simple but profound path to oxide semiconductor flexible electronics.