非均匀界面电荷对pMOS及TFT阈值电压的影响研究

发布时间：2018-02-12 05:35

本文关键词： pMOS器件负偏压温度不稳定性(NBTI) 器件模拟(TCAD) 阈值电压薄膜晶体管(TFT)　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着半导体技术的发展,器件日益小型化,pMOS器件的负温度不稳定效应NBTI(Negative Bias Temperature Instability)加剧,成为影响器件和相关电路寿命的主要因素,因而重新受到重视。在实际的物理实验中,往往热载流子效应、NBTI效应等多种退化同时发生,难以进行独立研究。而且随着器件的尺寸越来越小,实验测量的难度加大。传统的实验方法从经济和技术的角度都显示出了不足,因此使用数值模拟软件进行研究显得尤为重要。在实际情况中,器件的漏极会加偏压,这时导致的退化又称为带偏置DB-NBTI(Drain Bias NBTI)效应。与传统的NBTI效应不同,其退化产生的界面电荷在沟道方向上非均匀分布。这种非均匀分布的界面电荷对器件的影响,目前还未得到充分研究。本论文抓住这一机会,利用器件数值模拟软件,结合NBTI退化模型,分别研究了非均匀界面电荷pMOS器件和p沟道多晶硅薄膜晶体管TFT(Thin Film Transistor)的阈值电压退化特性。主要工作概括:(1)利用数值模拟软件Genius-Open,在沟道变化的情况下提取器件阈值电压,和电荷共享模型进行了拟合,并且研究了均匀界面电荷对pMOS器件阈值电压的影响,明确了构建器件模型的合理性,选取的退化模型、提取阈值电压方法的正确性。(2)通过将栅极分段,对界面电荷填充不同的浓度,模拟引入非均匀界面电荷的方法,研究了不同界面电荷的位置对pMOS阈值电压的影响,并通过研究不同情况下器件的表面势,探究了阈值电压变化的机理。(3)引入了分段连续分布的界面电荷,改变其浓度、分布长度,研究其对器件阈值电压的影响。并且对不同位置界面电荷之间的互相作用进行了探究。(4)最后,结合多晶硅陷阱分布模型,运用数值模拟商业软件Medici研究了p沟道TFT阈值电压,考虑和不考虑陷阱模型的情况都进行了讨论。分别设置了界面电荷不同的位置、浓度、连续分布长度,分析其对TFT阈值电压变化的影响。和以前的工作比较,引入变化的时间应力,研究了考虑陷阱模型TFT在漏极加偏压的情况下,随时间的退化特性。为进一步理论研究实际状况下TFT中NBTI退化奠定了一定基础。
[Abstract]:With the development of semiconductor technology, the negative temperature instability (NBTI(Negative Bias Temperature stability) of pMOS devices is becoming more and more small, which has become the main factor affecting the lifetime of devices and related circuits. Many kinds of degradation, such as the hot carrier effect and NBTI effect, occur at the same time, so it is difficult to carry out independent research, and as the size of the device becomes smaller and smaller, The difficulty of experimental measurement is increased. The traditional experimental methods are not enough in terms of economy and technology, so it is very important to use numerical simulation software to study them. In practice, the drain of the device will be biased. The resulting degradation is also known as the band-biased DB-NBTI(Drain Bias NBTI effect. Unlike the traditional NBTI effect, the interface charge generated by the degradation is distributed inhomogeneously in the channel direction, and the effect of the non-uniform distribution of the interfacial charge on the device. At present, it has not been fully studied. This paper takes this opportunity to use the device numerical simulation software, combined with the NBTI degradation model, The threshold voltage degradation characteristics of nonuniform interface charge pMOS devices and p-channel polysilicon transistor TFT(Thin Film transistors are studied respectively. The main work is summarized as follows: (1) using Genius-Open-numerical simulation software, the threshold voltage of the device is extracted under the condition of channel variation. The effect of uniform interface charge on threshold voltage of pMOS device is studied. The rationality of constructing device model and the degradation model are determined. The correctness of threshold voltage extraction method. (2) by dividing the grid electrode into different concentrations of interface charge and simulating the method of introducing non-uniform interface charge, the influence of the position of interface charge on the threshold voltage of pMOS is studied. By studying the surface potential of the device under different conditions, the mechanism of threshold voltage change is studied. Finally, combining with the polysilicon trap distribution model, the threshold voltage of p-channel TFT is studied by using the commercial software Medici. Considering and not considering the trap model, the effects of different positions of interface charge, concentration and continuous distribution length on the threshold voltage variation of TFT are analyzed, which are compared with previous work. By introducing the varying time stress, the degradation characteristics of the trap model TFT with time under the condition of drain bias are studied, which lays a foundation for the further theoretical study of NBTI degradation in TFT.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN386;TN321.5

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