亚微米级MOSFET器件模型分析及BSIM模型参数提取

发布时间：2018-06-08 04:26

本文选题：MOSFET电势模型 + 短沟道效应　；参考：《华北电力大学(北京)》2017年硕士论文

【摘要】：随着半导体器件的尺寸不断减小,短沟道效应和漏致势垒下降效应等次级物理效应不断增强,严重影响了器件性能,给器件和电路的仿真模拟带来了一系列的挑战。解析模型能够给出描述MOSFET在亚阈值状态下短沟效应对器件性能影响的解析表达式,因此精准的MOSFET解析电势模型是迫切需要的。论文首先对伯克利短沟阈值电压模型、电压-掺杂转换模型以及二维双区模型、单区模型在模型构建和解析方程方面做了详细描述。针对二维双区模型,为了提高其模型精度,改进了以下三个方面:一、增加了特征函数的展开项数;二、修改了源漏边界条件,小于结深的边界依然是常数电势,大于结深部分的边界条件采用了耗尽近似,称为浅结条件;三、考虑到小尺寸器件的耗尽层厚度会受漏电压等因素的影响,用电压-掺杂转换模型耗尽层厚度的计算方法校正了双区模型。同时定义了一个平均误差,该误差可以评测模型满足源漏边界条件的情况。由于伯克利短沟阈值电压模型是准二维模型,只能描述表面处的电势分布,本文将其拓展为二维模型使之能够得到二维电势分布,这样可研究衬偏效应对亚阈值摆幅的影响。和二维双区模型不同的是二维拓展的伯克利短沟阈值电压模型中源漏边界条件是常数。本文在不同衬底电压、沟道掺杂浓度和漏电压下,分别计算了双区和单区模型的源漏平均误差,发现双区模型的误差要小得多,并给出了两模型随栅长和漏电压减小的阈值电压滚降趋势,初步确定了双区模型具有更高的精度。计算了双区模型的亚阈值斜率,与伯克利短沟阈值电压模型及其二维拓展模型、电压-掺杂转换模型做了比较,结果显示双区模型的亚阈值斜率无论是变化趋势还是数值大小都与实验数据最为接近,且浅结条件要比常数条件更适合于小尺寸器件。同时发现对于二维拓展的伯克利短沟阈值电压模型,当结深远小于耗尽区厚度时,矩形求解区域的衬底边界电势斜率非零,表明源漏常数边界条件近似不成立。综上结果表明,校正后的双区模型在浅结边界条件时的精度最好。因为BSIM6.1模型在电路设计中更加方便,最后一章利用基因算法实现了BSIM6.1模型与BSIM3v3.2模型的参数转换。作为初步工作,我们在不考虑衬偏效应的情况下实现了利用BSIM6.1模型拟合BSIM3v3.2模型的I-V曲线。
[Abstract]:With the decrease of semiconductor device size, the secondary physical effects, such as short channel effect and leakage barrier drop effect, are increasing, which seriously affect the performance of semiconductor devices and bring a series of challenges to the simulation of devices and circuits. The analytical model can give an analytical expression to describe the effect of short-channel effect on the performance of MOSFET in sub-threshold state, so precise analytical potential model of MOSFET is urgently needed. In this paper, the Berkeley short-channel threshold voltage model, the voltage-doping conversion model, the two-dimensional two-zone model and the single-zone model are described in detail in terms of model construction and analytical equations. In order to improve the accuracy of the two-dimensional two-zone model, the following three aspects are improved: first, the expansion term of the eigenfunction is increased; second, the boundary condition of source and drain is modified, and the boundary less than the junction depth is still a constant potential. The boundary condition which is larger than the junction depth adopts the depletion approximation, which is called the shallow junction condition. Thirdly, considering that the thickness of the depletion layer of the small-sized device is affected by the leakage voltage and other factors, The two-zone model is corrected by calculating the depletion layer thickness of the voltage-dopant conversion model. At the same time, an average error is defined, which can be used to evaluate the condition that the model satisfies the boundary condition of source and drain. Since the Berkeley short-channel threshold voltage model is a quasi-two-dimensional model, it can only describe the potential distribution on the surface. In this paper, it is extended to a two-dimensional model so that the two-dimensional potential distribution can be obtained, so that the influence of the bias effect on the sub-threshold swing can be studied. Different from the two-dimensional two-zone model, the source and drain boundary conditions are constant in the two-dimension extended Berkeley short-channel threshold voltage model. In this paper, under different substrate voltages, channel doping concentrations and leakage voltages, the source and drain mean errors of two-zone model and single-zone model are calculated, respectively. It is found that the error of two-zone model is much smaller. The trend of threshold voltage rolling with the decrease of gate length and leakage voltage is given, and it is preliminarily determined that the two-zone model has higher accuracy. The sub-threshold slope of the two-zone model is calculated and compared with the Berkeley short-channel threshold voltage model and its two-dimensional expansion model, and the voltage-doping conversion model. The results show that the sub-threshold slope of the two-zone model is most close to the experimental data, and the shallow junction condition is more suitable for small-sized devices than the constant condition. It is also found that for the two-dimensional extended Berkeley short-channel threshold voltage model, when the junction depth is less than the depletion region thickness, the potential slope of the substrate boundary of the rectangular solution region is non-zero, which indicates that the boundary condition of the source and drain constant is approximately untenable. The above results show that the corrected two-zone model has the best accuracy under the shallow junction boundary condition. Because BSIM 6.1 model is more convenient in circuit design, in the last chapter, the parameter conversion between BSIM 6.1 model and BSIM3 v3.2 model is realized by genetic algorithm. As a preliminary work, the I-V curve of BSIM3 v3.2 model is fitted by BSIM6.1 model without considering the bias effect.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN386

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