Improvement on performance and reliability of TaN/HfO2 LTPS-TFTs with fluorine implantation

In this paper, we demonstrate the low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) with TaN metal-gate and HfO2 gate dielectric to achieve high performance characteristics. A high performance LTPS-TFT with low threshold voltage 0.9 V, excellent subthreshold swing 0.15 V/decade and high Ion/Imin current ratio 1.9 × 106 are derived without any hydrogen treatment. In addition, we also introduce the fluorine implantation prior to the Si thin-film crystallization to passivate the defects in grain-boundaries of the channel film and HfO2/polysilicon interface. Significant improvements on subthreshold swing and Imin are observed. In addition, the transconductance degradation and threshold voltage instability due to hot carrier stress is also investigated, respectively. Finally, we derive a high reliability and performance LTPS-TFT with low threshold voltage ∼1.38 V, ultra-low subthreshold swing 0.132 V/decade and high Ion/Imin current ratio 1.21 × 107, which is suitable for the application of system-on panel (SOP).