High-performance hydrogenated amorphous silicon TFT on flexible metal foil with polyimide planarization

We have studied the fabrication of hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) on flexible metal foil with polyimide planarization. The metal foil was coated with polyimide (PI) two times for palanarization with the total thickness of 2.6 μm. The PI was chosen because of its superior planarization capability, easy spin-on process and relatively high temperature process. To coat a PI layer two step process was carried out; room temperature coating and annealing at 180 °C for 1 h and then 300 °C curing for 1 h. The RMS surface roughness was changed from 663 to 20.6 Å by two times coatings. The a-Si:H TFT on the PI planarized metal foil exhibited the field-effect mobility of 1.47 cm2/V s and a threshold voltage of 1.8 V. The flexibility of the high-performance TFT was studied for AMOLED backplane application.