分立电荷俘获型存储器模拟研究

发布时间：2018-01-05 03:01

本文关键词：分立电荷俘获型存储器模拟研究　出处：《安徽大学》2012年硕士论文　论文类型：学位论文

【摘要】：随着传统浮栅存储器的尺寸缩小受到限制,急需要发展下一代非挥发存储器,目前对新一代非挥发存储器的研究非常广泛,有铁电存储器,阻变式存储器、纳米晶存储器,电荷陷阱存储器、相变存储器、有机物存储器等。其中分立电荷俘获型存储器的研究非常之多,其中电荷陷阱存储器(CTM:charge trapping memory)又是该领域的研究主流,它凭借其工艺与目j前主流CMOS工艺基本兼容的特性,CTM具有极大的潜力成为下一代非挥发存储器,从而率先占领新的存储器市场。传统浮栅存储器flash在小尺寸下存在严重的数据保持缺陷,浮栅阻挡层变薄,带来比较严重的信息泄露危险,因为薄的阻挡层在P/E过程中更容易产生缺陷,从而导致存储电荷一次性泄露。分立电荷俘获型存储器从理论上很好的解决这一问题,它利用电荷存储层中的分立陷阱来存储电荷的,从而将存储的电荷分立化,就算阻挡层中出现缺陷,也只能引起离缺陷最近的极小部分存储电荷的泄露,并不影响其存储信息的状态,从而保证存储器的正常工作。关于分立电荷俘获型存储器研究主要有三个大的方向,异是从结构上对电荷进行分立存储,如目前研究很多的纳米晶存储器；二是直接从存储材料入手,利用存储信息的化合物材料的分立陷阱来实现存储功能；三是将以上两种方法结合起来。采用纳米晶作为电荷存储介质,这种利用分立的纳米晶颗粒来实现电荷的分立存储,避免了传统浮栅闪存中因氧化层厚度变薄而引起信息泄漏的问题,在具有较好数据保持能力的情况下,能够相当程度的降低存储器件的操作电压。因而它也是下一代非易失性存储器的有力竞争者之一,引起广大研究者极大的兴趣。尽管分立电荷俘获型纳米晶存储器具有较快的擦／写速度、较低的操作电压等优势,但是尺寸缩小后,纳米晶的数量将会存在很大的限制,因为纳米晶数量越多,颗粒直径越大,存储性能越优越,这无疑是一对矛盾,而且不同器件在同一生产工艺下出来的数量可能都会波动,器件的均匀性也会受到较大影响。因此,我们仍需研究性能更为理想的非易失性存储器。与此同时发展起来的电荷陷阱存储器利用的是俘获层中材料本身的缺陷来存储电荷,利用不同材料中的陷阱,甚至通过对材料进行改性来获得更多的缺陷,进一步实现信息电荷的分立存储,它同时还可以实现多位存储,进而可以在相同的面积、技术条件下获得更高的存储密度,目前主流的电荷陷阱存储器结构SONOS至少可以达到22nm的工艺节点。由此可见,电荷陷阱存储器无疑有效的解决了很多问题,比如传统浮栅在小尺寸下的可靠性下降问题,突破了纳米晶存储器尺寸进一步缩小的瓶颈等等。综上,本文对分离电荷俘获型存储器展开了一系列的模拟研究,文章首先简单介绍了Flash memory的原理、结构与应用,接着突出介绍分立电荷俘获型存储器的主要结构原理及性能研究情况,第三章主要研究了纳米晶存储器结构对其存储性能的相关影响,第四章着重对CTM存储材料的模拟选取,以及其性能参数指标进行了着重的研究,采用新的视角与方法对CTM进一步研究起到了非常重要的借鉴作用,即采用了第一性原理对一些材料进行了深入的计算和分析,试图给CTM材料选取提供一套科学的解决方法,同时对存储材料中有效陷阱的选取也做了一定的模拟研究,从而进一步指导CTM实验的进行,对降低CTM研究成本,缩短其研究周期。最后综合总的研究,对本文的工作进行了总结跟展望。
[Abstract]:Along with the traditional floating gate memory size is limited, the urgent need to develop the next generation nonvolatile memory, the current research on a new generation of non-volatile memory is very extensive, with ferroelectric memory, resistive memory, nanocrystal memory, charge trap memory, memory, memory and other organic matter. The study of discrete charge trapping memory is very much, the charge trap memory (CTM:charge trapping memory) is the mainstream of the field, with its basic characteristics compatible with mainstream CMOS process technology and its J before, CTM has great potential to become the next generation nonvolatile memory, and memory to occupy the new market.
The traditional floating gate memory flash has serious defects on data retention in small sizes, the floating barrier layer becomes thin, bring more serious risk of information leakage, because the thin barrier layer in the P/E process is more prone to defects, resulting in storage charges leak at one time. The discrete charge trapping memory in theory is a good solution this problem, it uses the charge storage layer of discrete traps to store charge, which will store the charge separation, even if there is some defect in barrier layer, also can cause defects from the recent tiny part of stored charge leakage, does not affect the storage of information, so as to ensure the normal work of the memory. Study on discrete charge trapping memory there are three major directions, is different from the structure of the discrete storage charge, such as the current study of nanocrystal memory two is directly from the many; In the storage material, the storage function is realized by the discrete trap of the compound material that stores information; three is to combine the above two methods.
The nanocrystals as a charge storage medium, discrete storage such use of discrete nanocrystals to achieve charge, to avoid the traditional floating gate flash memory because of the oxide layer thickness caused by the problem of information leakage in the good data retention situation, to reduce the operating voltage when the storage device level. It is the next generation of non contenders lost memory, caused by the interests of many researchers. Although the discrete charge trapping nanocrystal memory has a faster Wipe / write speed, low voltage operation and other advantages, but the size reduced, the number of nanocrystals will have the very big limitation, because the more the number of nano particle diameter, the greater the storage performance more superior, this is a contradiction, and the number of different devices in the same production process may fluctuate,. The uniformity of the piece will also be greatly affected. Therefore, we still need to study the more ideal nonvolatile memory.
At the same time the development of charge trap memory using the defective material trapping layer itself to store charge, using different materials in the trap, even through the material was modified to obtain more defects, further realize the separation of information storage charge, and at the same time it can also realize storage, which can be in the same area to obtain higher storage density, technical conditions, process node current SONOS charge trap memory structure of the mainstream can reach at least 22nm. Thus, charge trap memory undoubtedly effective to solve a lot of problems, such as the reliability of traditional floating gate in small size of the decline, to break the bottleneck of nanocrystal memory size is further reduced and so on.
In summary, this paper carried out a series of simulation studies on the separation of charge trapping memory, this paper introduced the principle of Flash memory, structure and application, and then highlight main structure principle and Performance Research of discrete charge trapping memory, the third chapter mainly studies the nanocrystal memory structure effect on the storage performance the fourth chapter focuses on the simulation of CTM, storage material selection, as well as its performance.
The number of indicators were emphatically studies with a new perspective and methods to a very important reference for the further study of CTM, which is the first principle calculation is carried out in-depth analysis on some materials, trying to provide a scientific method to solve the CTM material selection, and selection of effective trap storage the material was also performed in a simulation study, to further guide the CTM experiment, CTM research to reduce the cost, shorten the research period. Finally the general research, this paper summarizes the work and prospects.

【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP333

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