The Threshold Voltage Model And Series Resistance Extraction Method Of Polycrystalline Silicon Thin Film Transistors

This paper proposed a threshold voltage (Vth) model and a series resistance (Rs) extraction method for polycrystalline silicon (poly-Si) thin film transistors (TFTs).Firstly, a physical-based analytical expression for Vth of poly-Si TFTs is proposed. This Vth model is derived by the second-derivative method and is based on the ON-state drain current model of poly-Si TFTs. The Vth is defined as the channel turn-on voltage, and includes not only the channel inversion but also the grain boundary (GB) potential barrier modulation effect and mobility degradation effect. Note that the GB barrier modulation is the dominate factor for the device Vth rather than the channel inversion. Besides, this model quantitatively described the"pseudo-subthreshold region"of poly-Si TFTs. The calculated Vth values agree well with the experimentally extracted ones.Secondly, a new Rs extraction method is proposed for poly-Si TFTs based on the ON-state drain current model. This proposed method is insensitive to channel length and mobility variation, and reasonable results can be obtained.