The fabrication of polysilicon thin film transistors by copper-induced lateral crystallization

The material properties and device characteristics of copper-induced polysilicon thin-film transistors (TFTs) are investigated. In preparation of polysilicon through copper-induced lateral crystallization, it was found that the growth rate of copper-induced polysilicon is approximately 4-14 times faster than that of Ni-induced polysilicon and the grain size is 10-20 times smaller. The nucleation mechanism induced by copper is the normal phase transition of the accumulated thermal effect while that induced by Ni is the migration of NiSi₂. The Cu-induced poly-Si TFT exhibits a field effect mobility of 24 cm²/V-sec, a threshold voltage of 6.6 V, and a subthreshold swing of 3.26 V/decade at a drain voltage V_DS=10 V.