Electrical Enhancement of Solid Phase Crystallized Poly-Si Thin-Film Transistors with Fluorine Ion Implantation

Solid phase recrystallized polycrystalline silicon thin-film transistors (SPC poly-Si TFTs) with fluorine ion implantation were investigated in this study. Electrical characteristics and reliability of the proposed poly-Si TFTs were improved effectively, especially for field effect mobility and off current. The fluorine-ion-implanted poly-Si TFT can suppress the hot carrier multiplication near the drain side, leading to superior endurance to electrical stress compared with conventional poly-Si TFTs. It was found that fluorine ions will pile up at the poly-Si interface during thermal annealing, without the initial deposition of pad oxide. The proposed technology is manageable and compatible with conventional poly-Si TFT fabrication. As the ion dosages increase more than 5 X 10 15 cm -2 , however, the electrical characteristics of poly-Si TFTs were degraded due to the increase of trap state density caused by the fluorine segregation in the poly-Si film.