标题: 高介电金属闸金氧半场效电晶体之随机扰动电子讯号:实验、建模与TCAD模拟
HKMG MOSFET Random Telegraph Signals (RTS): Experiment, Modeling, and TCAD Simulation
作者: 林煜翔
Lin, Yu-Hsiang
陈明哲
Chen, Ming-Jer
电子研究所
关键字: 随机扰动电子讯号;缺陷;RTS;trap
公开日期: 2012
摘要:   在体积更小、更快、更省电等等便利性和经济性的诉求下,电子元件尺寸的微缩便成为了未来的趋势。而随着电子元件尺寸的微缩,奈米尺度的随机扰动电子讯号(RTS, Random Telegraph Signals)也因而越来越不可忽视。因此,研究小尺寸元件中RTS对元件电性所带来的影响便成为了一门重要的课题。RTS现象的发生普遍认为是载子被氧化层中的缺陷重复进行捕捉-释放的过程。当载子被捕捉时,被捕捉的载子会在氧化层中产生一股额外的屏蔽库仑电位,它将影响到通道中的载子,使得汲极/源极的电流大小随着捕捉-释放的过程而在两个阶段间波动。在实验中,我们较不容易观察到汲极/源极的电流变化量和这些可能影响RTS的参数之间的关系。其中一个理由是,我们无法自由地改变实际的元件的各项参数以改变其物理特性,而另一个理由则是,我们难以在一片晶片上找到足够多具有RTS现象的元件。然而, TCAD模拟使得我们能够解决这些问题。在TCAD模拟中,我们可以藉由设定我们所需要的参数,像是闸极长度、闸极宽度、掺杂浓度等等来控制元件的特性,并且可以插入一个缺陷到矽氧化层中以确保此结构具有RTS的现象。
  本篇论文的主要目标是建立一个新颖的RTS物理模型。而在建立模型之前,我们须先量测实际的实验数据,再佐以TCAD的模拟来了解RTS的各种特性。首先,藉由TCAD的模拟,我们调整了MOSFET尺寸的大小、trap的大小、以及trap的位置。经由比较汲极/源极电流变化量和各种参数间的变化关系,我们能够得出随参数变化而导致的电流变化趋势:(1)汲极电流变化率会随着元件尺寸的渐小而渐增;(2) 汲极电流变化率的曲线图上会有一个最大值同时也是曲线的转折点,而此转折点的转折程度会随着元件尺寸的渐小而逐渐变得剧烈;(3)当两个元件有同样闸极宽度时,汲极电流变化率曲线在次临界电压区域时的斜率也会一样;(4)缺陷在闸极正中央的汲极/源极电流会比缺陷在闸极边缘的汲极/源极电流来得小;(5)缺陷靠近源极的汲极/源极电流会比缺陷靠近汲极的汲极/源极电流来得小。
  接下来在分析过模拟结果之后,我们假设当元件在次临界电压时,于相同的闸极偏压下,汲极电流变化率将只和元件宽度有关( )而并非同时与元件宽度以及长度有关( )。藉由从模型求出的缺陷尺寸来验证模拟跑出来的缺陷尺寸、以及由模拟跑出来的缺陷尺寸来验证模型求出的缺陷尺寸两个相反的方式,可以证明这个假设。以此结果为根据,将 和 两个模型藉由波兹曼函数合并起来,使得我们的新模型在次临界电压区域有 的特性、在强反转区域有 的特性。并且,为了使此模型能够应用在实际数据,我们适当地将其简化。
Due to the request for smaller, faster, and more efficient metal-oxide-semiconductor field-effect transistors (MOSFETs), down-scaling has become a current trend of device development. As the dimensions of device are scaled, random telegraph signals (RTS) play an important role in the development of scaling technologies. Hence, researching the electronic property in the presence of RTS in nano-scale devices is becoming a challenging issue. These signals are generally considered as carrier trapping-detrapping from a defect situated in the silicon oxide. When a carrier is trapped, the trapped carrier will produce an additional screened Coulomb potential in the silicon oxide affecting the carriers in channel, and it makes the drain/source current fluctuate between two discrete levels as a trapping-detrapping process. In the experiment, it is not easy to observe the relation between drain/source current variation and the parameters which may impact RTS phenomenon. The one reason is that we cannot modify the characteristic of real devices as we want, and the other reason is that it is difficult to find RTS events across the whole wafer. However, we can solve these problems by using TCAD simulation. In TCAD simulation, we can control the device characteristics by setting any parameters such as gate length, gate width, and doping concentrate, and insert a trap into silicon oxide to make sure the occurrence of RTS events in structure.
Building a new physical model of RTS is the major purpose in this thesis. Before building it, we have to characterize the practical device to get experimental data, and analyze its identity by simulating RTS phenomenon by TCAD. First, we built a MOSFET structure with different device sizes, different trap sizes, and different trap positions. By comparing the variation of drain/source current with different parameters, the trend of drain / source current variation changing with each of parameters can be obtained: (1) The rate of drain current change is larger when device size is smaller; (2) There is a peak in the curve for the rate of drain current change, and when device size is scaled, the peak will become sharper and sharper; (3) When the devices with the same width, the curve slopes for the drain current change rate in the subthreshold region are also the same; (4) Drain/source current of trap at gate center of device is smaller than trap at gate edge; and (5) Drain/source current of trap near the source is smaller than trap near the drain.
Second, after getting and analyzing the result, we assumed that in the same gate bias, the rate of drain current change would only relate to gate width ( ) instead of both gate width and gate length ( ) when it is in subthreshold region. Then, we verified the trap size in the TCAD simulation while determining the trap size in the model derivation; and vice versa. Based on the simulated result, we combined the two models into a new one using Boltzmann function so that there are two distinct characteristics, in subthreshold region and in strong inversion region. Then, it is a straight focused task to enable the application of the new model in the reproduction of experimental data.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079811527
http://hdl.handle.net/11536/46708
显示于类别:Thesis


文件中的档案:

  1. 152701.pdf

If it is a zip file, please download the file and unzip it, then open index.html in a browser to view the full text content.