發(fā)布時間：2018-03-10 21:00

  本文選題：雙柵MOSFET　切入點：圍柵MOSFET　出處：《江南大學》2015年碩士論文　論文類型：學位論文

【摘要】：隨著半導體技術的發(fā)展,常規(guī)二維金屬氧化物半導體場效應管(MOSFET)的特征尺寸已接近物理極限,并出現(xiàn)了許多非理想效應。而新型多柵MOS器件已從平面結構向雙柵(DG)、鰭柵、三柵、圍柵(SG)MOSFET等三維結構發(fā)展,其共同特征是隨著柵的數(shù)目增加,對溝道的控制能力增強,主要表現(xiàn)在反型層的體積增加,屏蔽了漏端電場對溝道中的電荷分享,從而增大了漏源電流,提高了帶負載能力,抑制了一些非理想效應。為了更好地了解和應用此類新型器件的優(yōu)良電學性能,本論文主要研究短溝道DG和SG MOSFET的電學特性,通過建立器件物理模型,討論器件結構參數(shù)和電學特性的關系,并提出一些抑制典型非理想效應的改進方案。論文首先采用電勢分解的方法,求解了短溝道本征或輕摻雜DG MOSFET溝道電勢的二維泊松方程,得到其電勢解析模型;在此基礎上給出了閾值電壓、亞閾值區(qū)電流和亞閾值擺幅模型的解析表達式,并分析了溝道長度、柵氧化層厚度和溝道寬度對閾值電壓、亞閾值區(qū)電流和亞閾值擺幅的影響。利用TCAD仿真工具Atlas進行了器件模擬,通過對比驗證了相關模型的準確性,歸納了器件參數(shù)對電學特性的影響規(guī)律。結果表明,當器件工作狀態(tài)為亞閾值區(qū)時,設計合理的溝道長度、寬度及柵氧化層厚度,可以提高DG MOSFET的亞閾值特性,抑制短溝道效應(SCE)的影響。其次,在已有短溝道無結柱狀SG MOSFET結構的基礎上,通過在求解溝道電勢時引入一維電勢,得到了電勢的表達式;在求解亞閾值區(qū)電流解析表達式時,采用泰勒級數(shù)展開并作合理近似,解決了直接積分比較困難的問題,并推導了亞閾值擺幅的表達式;討論了溝道長度、柵氧化層厚度和溝道直徑對亞閾值區(qū)電流和亞閾值擺幅的影響,并分析了亞閾值特性模擬結果和前人報道的實驗結果之間存在誤差的原因。結果表明,較薄的柵氧化層能增強柵極對溝道的控制,較大的溝道直徑能增大亞閾值擺幅。最后,在已有短溝道三材料柱狀SG MOSFET結構的基礎上,采用與前面類似的求解方法獲得了溝道電勢的表達式;推導了閾值電壓、亞閾值區(qū)電流和亞閾值擺幅的表達式;討論了溝道直徑、柵氧化層厚度和三柵長度比率對這些電學特性參數(shù)的影響,并分析了亞閾值特性模擬結果和前人報道的結果之間存在誤差的原因。結果表明,優(yōu)化三材料柵的柵長比率、選擇合適的柵氧化層厚度和溝道直徑,可以增強器件對SCE和漏致勢壘降低效應的抑制能力�？傊�,通過對短溝道DG、無結柱狀SG和三材料柱狀SG MOSFET相關電學模型的研究,有助于揭示這些新型MOS器件結構參數(shù)和電學特性的關系,為更好地應用它們提供有益的參考。
[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.
【學位授予單位】：江南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN386

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本文編號：1595046