【作者】 陆磊；

【导师】 王明湘；

【作者基本信息】 苏州大学 ， 微电子学与固体电子学， 2010， 硕士

【摘要】 多晶硅薄膜晶体管(TFT: Thin Film Transistor)在液晶显示中的广泛应用,使其越来越受到重视。但是,目前多晶硅TFT的表征方法还主要集中在源漏端和栅极端。本文成功将通用的MOSFET的衬底端表征方法——电荷泵技术(CP: Charge Pumping)和衬底电流(Isub)引入到多晶硅TFT的研究中。首先,通过调整栅脉冲的上升沿和下降沿时间的方式首次消除了CP电流(Icp)中的几何因素,从而达到优化CP的目的。采用优化的CP,在多晶硅TFT中获得了和MOSFET中类似的帽子型Elliot曲线。然后,基于通用的CP模型,建立了TFT中Elliot曲线的模型。另外,利用优化的CP获得了缺陷态密度(Dt: Trap Density)的典型能级分布,并用多种方法可靠地提取了Dt的平均值。更进一步,首次提出了一种能够自动规避几何效应影响的新型Dt提取方法。另外,还利用CP研究了TFT的退化。另一方面,本文首次研究了多晶硅TFT中的Isub。当衬底偏压(Vsub)较小时,Isub来源于发生在沟道内的复合过程,因而和Dt直接相关。并且,在Vg的调控下,复合区可以从整个沟道变化到靠近源漏端或者衬底端附近的局部区域。基于Isub的这种机制,建立了Isub-Vg曲线的模型。最后,利用Isub-Vg曲线精确地探测了热载流子应力造成的损伤区的位置及其内部的Dt的变化。更多还原

【Abstract】 As polysilicon thin film transistors (TFTs) have been widely used in liquid crystal display, it becomes more and more important to study polysilicon TFTs. However, up to the present, the evaluation approaches in polysilicon TFTs are mainly at the source and drain terminals. In this paper, as general approaches at substrate terminal in MOSFETs, the charge pumping (CP) and substrate current (Isub) are applied to polysilicon TFTs.At first, CP is firstly optimized by adjusting the gate pulse transition times to eliminate the geometric component of the CP current (Icp). Improved Elliot curves similar to those in MOSFETs are obtained for polysilicon TFTs. Then, according to the general CP model, the model for Elliot curves of polysilicon TFTs is proposed. Besides, based on the improved CP, typical trap state density (Dt) energy distribution within upper part of the band-gap and mean Dt value ( Dt ) are reliably extracted in different approaches. Furthermore, a modified Dt extraction approach, where the influence of the CP geometric component is inherently avoided, is first proposed. In addition, CP is employed to investigate the degradation of TFTs.On the other hand, Isub in polysilicon TFTs is first studied. When the substrate voltage (Vsub) is very small, Isub is found to be driven by the recombination process and therefore relevant to Dt. Furthermore, controlled by Vg, the recombination area can vary from the whole channel area to the local region near drain, source or substrate terminal. Based on the mechanism, the model for the Isub-Vg curve is built. Finally, the Isub-Vg curve is applied to sensitively locate the hot carrier damage region and detect the locally increased Dt in this area.更多还原