Hysteresis Improvement of Low-Temperature Polycrystalline Silicon Thin-Film Transistors by N₂O Plasma Surface Treatment

초록

We investigated the effects of O2 annealing and N2O plasma surface treatment on polycrystalline silicon (poly-Si) to improve hysteresis of low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs). The O2 annealing surface-treated LTPS TFTs exhibited a reduction in the subthreshold swing (SS). However, hysteresis improvement was not significantly observed compared to the non-treated LTPS TFTs. However, the N2O plasma surface-treated LTPS TFTs exhibited a greater reduction in SS and hysteresis improvement than the O2 annealing surface-treated LTPS TFTs. These results originated from the reduction of trap states at the interface between poly-Si and the gate insulator. Compared to O2 annealing surface treatment, N2O plasma surface treatment makes the interface more stable because oxygen passivates the trap states and diffuses into poly-Si. However, as radio-frequency (RF) power increased, SS and hysteresis characteristics degraded due to ion bombardment. Consequently, we improved the hysteresis of LTPS TFTs through N2O plasma surface treatment on poly-Si by optimizing the RF power conditions.

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