短沟道双栅和围栅MOSFET的建模和电学特性研究

发布时间：2018-03-10 21:00

本文选题：双栅MOSFET　切入点：围栅MOSFET　出处：《江南大学》2015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,常规二维金属氧化物半导体场效应管(MOSFET)的特征尺寸已接近物理极限,并出现了许多非理想效应。而新型多栅MOS器件已从平面结构向双栅(DG)、鳍栅、三栅、围栅(SG)MOSFET等三维结构发展,其共同特征是随着栅的数目增加,对沟道的控制能力增强,主要表现在反型层的体积增加,屏蔽了漏端电场对沟道中的电荷分享,从而增大了漏源电流,提高了带负载能力,抑制了一些非理想效应。为了更好地了解和应用此类新型器件的优良电学性能,本论文主要研究短沟道DG和SG MOSFET的电学特性,通过建立器件物理模型,讨论器件结构参数和电学特性的关系,并提出一些抑制典型非理想效应的改进方案。论文首先采用电势分解的方法,求解了短沟道本征或轻掺杂DG MOSFET沟道电势的二维泊松方程,得到其电势解析模型;在此基础上给出了阈值电压、亚阈值区电流和亚阈值摆幅模型的解析表达式,并分析了沟道长度、栅氧化层厚度和沟道宽度对阈值电压、亚阈值区电流和亚阈值摆幅的影响。利用TCAD仿真工具Atlas进行了器件模拟,通过对比验证了相关模型的准确性,归纳了器件参数对电学特性的影响规律。结果表明,当器件工作状态为亚阈值区时,设计合理的沟道长度、宽度及栅氧化层厚度,可以提高DG MOSFET的亚阈值特性,抑制短沟道效应(SCE)的影响。其次,在已有短沟道无结柱状SG MOSFET结构的基础上,通过在求解沟道电势时引入一维电势,得到了电势的表达式;在求解亚阈值区电流解析表达式时,采用泰勒级数展开并作合理近似,解决了直接积分比较困难的问题,并推导了亚阈值摆幅的表达式;讨论了沟道长度、栅氧化层厚度和沟道直径对亚阈值区电流和亚阈值摆幅的影响,并分析了亚阈值特性模拟结果和前人报道的实验结果之间存在误差的原因。结果表明,较薄的栅氧化层能增强栅极对沟道的控制,较大的沟道直径能增大亚阈值摆幅。最后,在已有短沟道三材料柱状SG MOSFET结构的基础上,采用与前面类似的求解方法获得了沟道电势的表达式;推导了阈值电压、亚阈值区电流和亚阈值摆幅的表达式;讨论了沟道直径、栅氧化层厚度和三栅长度比率对这些电学特性参数的影响,并分析了亚阈值特性模拟结果和前人报道的结果之间存在误差的原因。结果表明,优化三材料栅的栅长比率、选择合适的栅氧化层厚度和沟道直径,可以增强器件对SCE和漏致势垒降低效应的抑制能力。总之,通过对短沟道DG、无结柱状SG和三材料柱状SG MOSFET相关电学模型的研究,有助于揭示这些新型MOS器件结构参数和电学特性的关系,为更好地应用它们提供有益的参考。
[Abstract]:With the development of semiconductor technology, the characteristic size of conventional two-dimensional metal oxide semiconductor field effect transistor (MOSFETs) has approached the physical limit, and many non-ideal effects have appeared. The common feature of the development of three dimensional structures, such as SGN MOSFET, is that with the increase of the number of gates, the control ability of the channel is enhanced, which is mainly manifested in the increase of the volume of the inversion layer, which shields the electric field at the end of the drain from the charge sharing in the channel. In order to better understand and apply the excellent electrical properties of these novel devices, the electrical properties of short channel DG and SG MOSFET are studied in this paper. By establishing the physical model of the device, the relationship between the structure parameters and the electrical characteristics of the device is discussed, and some improved schemes to suppress the typical non-ideal effects are proposed. Firstly, the method of potential decomposition is used in this paper. The 2-D Poisson equation of short channel eigenvalue or lightly doped DG MOSFET channel potential is solved, and the analytical model of its potential is obtained, and the analytical expressions of threshold voltage, sub-threshold current and sub-threshold swing model are given. The effects of channel length, gate oxide thickness and channel width on threshold voltage, subthreshold current and sub-threshold swing are analyzed. The device is simulated by TCAD simulation tool Atlas, and the accuracy of the model is verified by comparison. The effects of device parameters on electrical properties are summarized. The results show that the subthreshold characteristics of DG MOSFET can be improved by designing reasonable channel length, width and gate oxide thickness when the device is in the sub-threshold region. Secondly, on the basis of the existing columnar SG MOSFET structure of short channel without junction, the expression of potential is obtained by introducing one-dimensional potential into the solution of channel potential, and the analytical expression of current in sub-threshold region is obtained. By using Taylor series expansion and reasonable approximation, the difficulty of direct integration is solved, the expression of sub-threshold amplitude swing is derived, and the channel length is discussed. The effects of gate oxide thickness and channel diameter on the current and amplitude of sub-threshold range are analyzed. The reasons for the error between the simulation results of sub-threshold characteristics and the experimental results reported by others are analyzed. The thin gate oxide layer can enhance the grid control over the channel, and the larger channel diameter can increase the sub-threshold swing. Finally, based on the existing short channel three-material columnar SG MOSFET structure, The expressions of channel potential, threshold voltage, subthreshold current and sub-threshold amplitude are derived by using a similar solution method, and the channel diameter is discussed. The influence of the thickness of gate oxide and the ratio of three gate length on these electrical characteristic parameters is also analyzed. The reasons for the error between the simulation results of subthreshold characteristics and those reported by others are analyzed. The results show that the gate length ratio of three materials is optimized. Selection of appropriate gate oxide thickness and channel diameter can enhance the ability of the device to suppress the SCE and drain induced barrier reduction effects. In a word, the related electrical models of short channel DG, columnar SG without junction and columnar SG MOSFET with three materials are studied. It is helpful to reveal the relationship between the structural parameters and electrical properties of these new MOS devices and to provide a useful reference for their better application.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN386

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