A high performance amorphous silicon thin film transistor with a planarized gate

The hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with a SiN x /BCB gate insulator have been studied. The gate planarization was carried out by spin-coating of BCB (benzocyclobutene) on Cr gates. The threshold voltage of a-Si:H TFTs increases with BCB thickness due to the low dielectric constant (2.7) of BCB. The a-Si:H TFT with a SiN x (100 nm)/BCB(100 nm ) gate insulator exhibited a field effect mobility of 0.96 cm 2 /Vs in the linear region, which is about 20 % higher than that of conventional a-Si:H TFT. The BCB exhibits charge trappings during high gate bias, but the stability of the TFT is the same as conventional one when gate bias is between -25 V and + 25 V.